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Psychosocial determinants of parental human papillomavirus (HPV) vaccine decision-making for sons: Methodological… Perez, Samara; Tatar, Ovidiu; Shapiro, Gilla K; Dubé, Eve; Ogilvie, Gina; Guichon, Juliet; Gilca, Vladimir; Rosberger, Zeev Dec 5, 2016

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RESEARCH ARTICLE Open AccessPsychosocial determinants of parentalhuman papillomavirus (HPV) vaccinedecision-making for sons: Methodological(T1) and 1,427 (T2) were retained. Less than 3% of boys were vaccinated at both time points. At both T1 and T2,most parents (over 70%) belonged to the earlier vaccination adoption stages: 57% were unaware (T1) and 15.3%Perez et al. BMC Public Health  (2016) 16:1223 DOI 10.1186/s12889-016-3828-9Cote Ste-Catherine Road Room 214, Montreal, QC H3T 1E4, CanadaFull list of author information is available at the end of the article1Department of Psychology, McGill University, 1205 Dr. Penfield Avenue,Montreal, QC H3A 1B1, Canada2Lady Davis Institute for Medical Research, Jewish General Hospital, 4333HCP about the HPV vaccine for their son.(Continued on next page)* Correspondence: samara.perez@mail.mcgill.ca(T2); 20.9% were unengaged (T1) and 32.4% (T2); and 9.1% were undecided (T1) and 25.2% (T2). At follow-up,37.7% of participants did not move from their initial PAPM decision-making stage. Most parents (55%) preferred toreceive information from their healthcare provider (HCP) but only 6% (T1) and 12% (T2) had actually spoken with achallenges and initial results of apan-Canadian longitudinal studySamara Perez1,2* , Ovidiu Tatar2, Gilla K. Shapiro1,2, Eve Dubé3, Gina Ogilvie4, Juliet Guichon5, Vladimir Gilca3and Zeev Rosberger1,2,6AbstractBackground: HPV vaccination decision-making is a complex process that is influenced by multiple psychosocialdeterminants. Given the change in policy recommendation to include males in routine HPV vaccination, our goalswere to assess the HPV vaccination uptake in Canada, to understand where Canadian parents were situated in theHPV vaccine decision-making process for their son, how they changed over time and which psychosocialdeterminants were relevant for this process.Methods: We used an online survey methodology and collected data from a nationally representative sample ofCanadian parents of boys aged 9–16 at baseline (T1, February 2014) and at 9 months’ follow-up (T2). Our analyseswere guided by the Precaution Adoption Process Model (PAPM), a theoretical health behavior model that classifiesparents in one of six stages: unaware, unengaged, undecided, decided not to vaccinate, decided to vaccinate andthose who had already vaccinated their sons. Rigorous methods were used to filter out careless responders:response variance, bogus items, psychometric antonyms and psychometric synonyms.Results: At T1 and T2, we received 3,784 and 1,608 respectively completed questionnaires; after data cleaning 3,117© The Author(s). 2016 Open Access This article is distributed under the terms of the Creative Commons Attribution 4.0International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, andreproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link tothe Creative Commons license, and indicate if changes were made. The Creative Commons Public Domain Dedication waiver(http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated.aprVpaoloccenPerez et al. BMC Public Health  (2016) 16:1223 Page 2 of 17argued for vaccination of males [14]. Inclusion of malesin HPV immunization programs grew further because:1) HPV vaccine uptake rates among females are failingto reach sufficient levels (of at least 70%) to confer herdimmunity to heterosexual males, 2) female-only pro-grams do not offer protection to men having sex withmen (MSM); and 3) a gender specific vaccine raises is-sues of equity [14–22].Presently, all Canadian provinces and territories offerfree, school-based HPV vaccination programs for females.ioral research has been conducted among samples offemales or parents of daughters [31, 37]. To the best ofour knowledge, there are very few studies examining HPVvaccine decision-making that were conducted exclusivelyamong parents of boys [35, 37]. In the Canadian context,only two studies outside the present one examine thepsychosocial decision-making process among Canadianparents of sons; both studies were conducted before theHPV vaccine was recommended for males and thereforethe outcome variable reflects intentions to vaccinate ratherburden of HPV-associated diseases in males, many[13]. As the research evidence grew, demonstrating the Because HPV was traditionally considered an (an infec-tion) that affects females only, the vast majority of behav-(Continued from previous page)Conclusions: HPV vaccination uptake in Canadian boys wvaccination programs for boys. Optimal HPV informationinterventions to increase HPV knowledge and increase HPspeak to one’s HCP did not translate into action for mostto consider to inform implementation strategies. Methodfuture research are offered.Keywords: Human papillomavirus, Cancer prevention, VaHealth behavior, Precaution Adoption Process Model, ParBackgroundThe prevention of human papillomavirus (HPV)-associ-ated diseases is an increasingly prominent public healthissue. HPV is the most common sexually transmitted in-fection (STI) and accounts for 4.8% of the worldwidecancer burden [1, 2]. HPV has been traditionally viewedas an infection that impacts females [3, 4], even thoughit poses a significant disease burden for males. Currentdata suggests that 100% of cervical, 88% of anal, 70% ofvaginal, 50% of penile, 43% of vulvar and 13–56% of oro-pharyngeal cancers are attributable to HPV [3]. Like fe-males, males are at risk also for contracting HPV-associated genital warts (GW), which can negativelyimpact quality of life [3].The quadrivalent vaccine, Gardasil® (Merck) protectsagainst four strains of HPV: two oncogenic strains (HPV16, 18), and two that cause GW (HPV 6 and 11) [5].Epidemiological studies from Australia, Canada, UK andthe US demonstrate population level reductions in therates of HPV, GW, and cervical cancer lesions after intro-duction of HPV vaccine programs for girls [6–11]. Withstrong empirical evidence for both vaccine safety and effi-cacy [5], the HPV vaccine is an important innovation incancer prevention [6, 12].In 2007, in Canada, the HPV vaccine (Gardasil®) wasrecommended for females and subsequently rolled outfor females only in school-based immunization programsCanada’s National Advisory Committee on Immunization(NACI, 2012 and 2015) recommends HPV vaccine forfemales and males aged 9–26 [2]; this recommendation iss very low in the absence of a publicly funded HPVeferences were identified and can be used invaccine uptake. Intentions to vaccinate or planning torents over the 9-month follow up; this finding is criticalgical challenges are described and suggestions forination, Determinants of health, Health decision-making,ts, Boys, Knowledge, Attitudes, Beliefsconsistent with that of other nations (e.g., US [23]Australia [24] and some of the European Union, e.g.Germany (Saxony), Italy (Emilia-Romagna, Sicily) [25, 26].In February 2013, Australia was the first country to extendnational vaccination programs for boys. In Canada, theHPV vaccination program for males has unfolded asfollows. In September 2013, Prince Edward Island (PEI)began including boys in grade 6 in their school-basedHPV vaccination programs. Alberta and Nova Scotiasubsequently followed in September 2014 for grade 5 boysand in autumn 2015 for grade 7 boys respectively. InSeptember 2015, British Columbia (BC) began offeringthe HPV vaccine without cost for “at risk” males e.g.,MSM and ‘street-involved’ youth [27]. Similarly, as ofJanuary 2016, Quebec offers the HPV vaccine withoutcost to MSM aged 9–26. Beginning in September 2016,Ontario, Quebec and Manitoba will include boys in theirschool-based programs (grades 7, 4 and 6, respectively)[14, 28]. In contrast with the female programs, onlyAlberta and Ontario offer catch-up programs for olderboys. When this research study was developed (2012), noHPV vaccinations programs for males existed in Canadaor elsewhere in the world.The examination of the attitudinal, behavioral, cognitive,social, cultural and logistical determinants (hereafter re-ferred to as psychosocial) that influence the HPV-vaccinedecision-making is a growing area of research [29–36].than actual vaccination uptake [38, 39].Further, experts in HPV vaccine behavioral research rec-ommend using theoretical health behavior frameworks toPerez et al. BMC Public Health  (2016) 16:1223 Page 3 of 17better understand the psychosocial determinants thatinfluence an individual’s vaccine decision-making process[30, 40, 41]. Many studies that examine the correlates ofHPV vaccine decision-making utilize the Health BeliefModel (HBM) [31, 42]. The linear HBM attempts tounderstand better HPV vaccine decision-making by focus-ing on attitudes and beliefs about the costs and benefits ofHPV vaccination that are relevant only to people who havebeen engaged (or are presumed to be engaged) sufficientlyby the HPV vaccination to have formed such beliefs [43].As such, most existing studies examine the psycho-social determinants that predict vaccination intentionsand/or uptake are for a group of individuals who areassumed to be already aware and engaged in HPVvaccination [31, 37, 42]. Since this group does notinclude everyone—and with respect to HPV vaccin-ation likely captures few parents because HPV vaccin-ation for males is relatively new and many parentsmay not yet have formed their beliefs—there arelikely other stages in adopting HPV vaccination. ThePrecaution Adoption Process Model (PAPM) is a cat-egorical stage theory, which aims to identify all thestages involved when people commence health-protective behaviors. The PAPM is therefore appropri-ate to apply to parental decision-making about HPVvaccination to determine the psychosocial determi-nates that lead parents to move from one stage to thenext, and ultimately to vaccinate their child [44].The PAPM consists of six1 distinct stages of healthdecision-making: 1) unaware of the health behavior); 2)unengaged in the decision; 3) undecided; 4) decided notto act; 5) decided to act (intending); and 6) acting (vacci-nated). As opposed to linear models, the PAPM stagedmodel acknowledges the fact that transition betweenstages can be explained by different psychosocial deter-minants, i.e. there are differences between determinantswhich influence the transition from stage 1 to 2 com-pared to the determinants which influence the transitionfrom stage 5 to 6.Using a longitudinal design and online survey meth-odology guided by the PAPM, we surveyed a nationalsample of Canadian parents of boys to understandwhere Canadian parents currently stand in the HPVvaccine decision-making process for their son andwhich psychosocial determinants influence their HPVvaccination decision-making process. Importantly, thepresent study was conducted just before severalCanadian provinces began to include males in theirschool-based public vaccination program. This createda unique opportunity to provide baseline data aboutHPV vaccine uptake in the absence of publicly fundedprograms, and to evaluate the impact of recentrecommendations of male HPV vaccination.The study objectives were:1. To provide an estimate of HPV vaccine uptakeamong males in Canada;2. To classify where Canadian parents’ stand in theHPV vaccine decision-making process for their son(s) using the PAPM, at baseline (Time 1, T1) and atfollow-up 9 months later (Time 2, T2);3. To describe how Canadian parents’ changed in theirHPV vaccine decision-making process from T1 tofollow-up (T2); and4. To describe and analyze which psychosocialdeterminants influence parents’ HPV vaccinedecision-making process i.e., PAPM stageThis research article will present a comprehensive de-scription of the study methodology, sample characteristicsas well as the results for objectives 1–3. Descriptive resultfor objective four, specifically for the following psycho-social determinants: HPV and HPV vaccine Knowledge,HPV vaccination information sources, health behaviors(i.e., primary decision-maker, routine check-ups with ahealthcare provider (HCP), and childhood immunizationpractices) and implementation intentions will be pre-sented. A more comprehensive statistical analysis of thepsychosocial determinants of PAPM stages over time i.e.,objective 4, is under way.MethodsRecruitmentThe population of interest was Canadian parents and/orguardians (hereafter referred to as parents) of 9–16 year-old boys. We selected this population because it coversthe current NACI HPV vaccine recommendation formales aged 9–26, and because after the age of 16, virtu-ally all Canadian minors may make a vaccination choicewithout parental consent [45, 46]. Data collection wasfacilitated by Leger2 a polling and market research firmthat maintains a national panel of 400,000 Canadiansacross the 10 provinces. The first wave of data collectionoccurred between February 7 and 25, 2014. E-mail invi-tations to complete a ~20-min online questionnaire weresent to 29,867 panelists who met the study’s inclusioncriteria (i.e., those who had a 9–16-year-old son living intheir household) according to data Leger maintains ontheir panelists. These invitations were followed by16,004 reminder emails (between 1 and 3 emails per par-ticipant). The second wave of data collection occurredbetween October 27 and November 19, 2014. E-mailinvitations were sent to 3,135 participants who wereeligible from T1 to participate at T2. These invitationswere followed by 8,341 reminder emails were (between 1and 5 emails). At the time of data collection, HPV vac-cination for males in Canada was just commencing; PEIhad initiated a school-based HPV vaccination programfor boys five months before (~Sept 2013) our T1 datacollection, while Alberta followed one month ahead of(~Sept 2014) our T2 data collection. See Fig. 1 for adetailed schematic of study participants following studyrecruitment and data cleaning.ProcedurePrior to beginning the questionnaire, participants wereasked first if they prefer to answer the questionnaire inEnglish or French and were provided the questionnaire inthe language of preference. Participants were also asked toagree to answer the questions truthfully and thoughtfullyor were excluded from completing the study. Participantswere also asked at the beginning of the questionnaire toprovide a name, nickname, initials or abbreviations fortheir son who is between the ages of 9 and 16 and whohas had the nearest birthday. Using intelligent program-ming, the provided sons’ initials, name or nickname (e.g.,Dan) was then replaced for my son in most items, makingthe questionnaire individualized for each participant. Inthis way, participants were asked about their beliefs andattitudes relative to one specific son. Participants wereinformed that their son’s name will not be used in anyother way by the researchers. Participants were requiredto complete every item, obviating the problem of missingdata. For 16 sensitive questions, “I prefer not to answer”was a response option provided. In order to further ensurerecollection of answering the questionnaire at T1,participants were asked at T2 “Do you remembercompleting the survey related to the HPV vaccine aboutmy son?” Participants who indicated no recollection werenot invited to participate at T2. Respondents werecompensated 3$ per completed questionnaire at both T1and T2.MeasuresQuestionnaire developmentA 2010 systematic review of measures used in HPV vaccineacceptability research called for standardized theoreticalPerez et al. BMC Public Health  (2016) 16:1223 Page 4 of 17Fig. 1 Flow diagram of study participantsPerez et al. BMC Public Health  (2016) 16:1223 Page 5 of 17and operational definitions of constructs [33]. This recom-mendation included: 1) utilizing theory to guide constructdefinitions [47, 48]; 2) employing cognitive testing [49]; 3)reviewing measures by panels of experts [39, 47, 48, 50]; 4)measuring intentions and actual behavior through cleardefinitions (e.g., asking about compliance to recommendednumber of doses) [51]; and, 5) development of con-structs to take into account language and literacylevels [48, 49, 52]. Our questionnaire development ad-hered to all five recommendations, including a ‘thinkaloud’ pilot testing of the questionnaire with 20 parents of9–16-year-old boys. The questionnaire was developed,reviewed and approved by a bilingual panel of seven expe-rienced HPV researchers.The English questionnaire was translated into French bya specialized translation firm and reviewed for accuracy byan independent bilingual group of professionals (n = 5)working in the healthcare field. The questionnaires werevirtually identical at T1 and T2 except for minor differ-ences (e.g., demographic items were removed at T2; itemsrelated to conspiracy beliefs were added at T2). Thecomplete questionnaire3 contained 165 items at T1 and191 items at T2, and is available by contacting the corre-sponding author. A summary of the questionnaire con-structs, sample items and response options are providedin Additional file 1.Socio-demographics (12 items)The first 12 items were standard socio-demographicvariables (e.g., province, education, religion) selectedfrom Statistics Canada 2011 Census questionnaire. Wecompared our sample to data the authors requestedfrom Statistics Canada’s National Household Survey(2011) of participants who met our inclusion criteria i.e.,parents of 9–16-year-old sons (n = 2,336,115) residing inthe 10 Canadian provinces in order to assure thegeneralizability of our results to the entire Canadianpopulation. First, chi-square tests were performed toexamine if there were any significant differences insocio-demographics between our T1 and T2 samples.Next, chi-square tests were performed to examine ifthere were any significant differences in socio-demographics between T1 and Statistics Canada’ssample (see Table 1). Because statistical significantdifferences (p < 0.05) in proportions do not indicate thesize of the difference, we further calculated Cohen’s h[53] (see Table 1). Consistent with Cohen’s recommen-dations, we interpreted h ≤ 0.2 as small, h = 0.5 asmedium and h ≥ 0.8 as a large difference [53].PAPM stage (1 item)The primary outcome variable in our study was parents’self-reported HPV vaccine decision-making stage, i.e.,PAPM stage. Parents were asked: “Before today, whichof the following best describes your thoughts about theHPV vaccine concerning my son?” Six response optionswere provided which allowed us to classify parentsaccording to six distinct categorical stages of HPV vac-cine decision-making (see Additional file 1). Of note,after assessing socio-demographics and HPV and HPVvaccine knowledge and just prior to assessing the outcomevariable i.e., PAPM stage, participants were provided witha brief informative statement about HPV and the HPVvaccine in order to ensure that they had some basicawareness as to what HPV and the HPV vaccine was4.Psychosocial determinantsHPV and HPV vaccine knowledge items (36 items)There is mixed evidence for the relationship betweenHPV-general and HPV-vaccine knowledge and parents’HPV vaccination intentions/uptake for their child [40, 54,55]. In order to assess what parents know about HPV andthe HPV vaccine, we utilized Waller and colleagues exist-ing psychometrically-tested, validated 16-item HPV and 7-item HPV vaccine scales [56]. We added 9 general HPVknowledge items and 4 HPV-vaccination specific itemsthat were missing from the scale (e.g., items assessingabout whether parents know about the link between HPVand other HPV-associated cancers beyond cervicalcancer), (see Additional File 1). Items answered correctlywere assigned 1 point while incorrect and “don’t know”were assigned 0 points to generate a total HPV-generaland HPV vaccine knowledge scores.Attitudes and beliefs (61 Items)HPV-specific vaccination attitudes and general vaccine be-liefs has been associated with parental vaccination inten-tions and uptake [37, 57]. The authors generated a list of200 potential attitudinal items found after reviewing thepsychosocial HPV vaccine literature and selected itemsbased on constructs derived from different theoreticalmodels of health behavior, including the HBM and theTheory of Reasoned Action) [58]. For each attitude andbelief item, a 7-point Likert response format with 1 =Strongly Disagree, 4 = Neutral and 7 = Strongly Agreewas used (see Additional file 1).Information sources (6 items), health behaviors (6 items),implementation intentions (3 items) and other itemsParticipants were asked about the sources where theyactually heard about the HPV vaccine and the sourcesthey would prefer receiving information about the HPVvaccine. They were also asked if, and what type ofrecommendation (for, against, neutral, or neither) theyreceived from a HCP for their son concerning the HPVvaccine. Self-reported health behaviors were also assessede.g., whether their son has attended a routine medicalcheck-up in the past year, acceptance of all theTable1Socio-demographicsforT1,T2andStatisticsCanadanationalhouseholdsurveysamples.TestofproportionsandeffectsizebetweenT1toT2andT1toStatisticsCanadasampleTime1n=3117Time2n=1427StatCann=2336115T1:T2EffectsizeCohen’shT1:StatCanEffectsizeCohen’shn%n%n%χ2valuepvalueχ2valuepvalueProvinceAlberta31910.214410.126511011.3χ2<0.01p=0.92h<0.01χ2=3.73p=0.05h=-0.04BritishColumbia33210.71309.129740012.7χ2=2.38p=0.12h=0.05χ2=11.93p<0.001h=-0.07Manitoba1203.8533.7890703.8χ2=0.02p=0.90h<0.01χ2<0.01p=0.95h<0.01NewBrunswick902.9362.5497152.1χ2=0.36p=0.55h=0.02χ2=8.25p<0.01h=0.05NewfoundlandandLabrador642.1201.4342101.5χ2=1.95p=0.16h=0.05χ2=7.07p<0.01h=0.05NovaScotia1384.4503.5610052.6χ2=1.88p=0.17h=0.05χ2=39.62p<0.001h=0.10Ontario92629.740028.093875040.2χ2=1.25p=0.26h=0.04χ2=141.71p<0.001h=-0.22PrinceEdwardIsland260.870.5103750.4χ2=1.16p=0.28h=0.04χ2=9.83p<0.01h=0.05Quebec102032.756639.750664021.7χ2=20.44p<0.001h=-0.14χ2=222.49p<0.001h=0.25Saskatchewan822.6211.5748403.2χ2=5.42p=0.02h=0.08χ2=3.11p=0.08h=-0.03LanguageBilingual551.8321.5345602.2χ2=0.95p=0.33h=-0.03χ2=1.55p=0.21h=0.02English18395975653123870553.0χ2=14.24p<0.001h=0.12χ2=44.38p<0.001h=0.12French10303356039.243222018.5χ2=16.26p<0.001h=-0.13χ2=435.30p<0.001h=0.34Other1916.1785.563063027.0χ2=0.66p=0.42h=0.03χ2=687.17p<0.001h=-0.59Perez et al. BMC Public Health  (2016) 16:1223 Page 6 of 17Table1Socio-demographicsforT1,T2andStatisticsCanadanationalhouseholdsurveysamples.TestofproportionsandeffectsizebetweenT1toT2andT1toStatisticsCanadasample(Continued)Time1n=3117Time2n=1427StatCann=2336115T1:T2EffectsizeCohen’shT1:StatCanEffectsizeCohen’shn%n%n%χ2valuepvalueχ2valuepvalueGenderMale99832.046032.2107520046.0χ2=0.01p=0.91h<-0.01χ2=245.30p<0.001h=-0.29Female211968.096767.8126091054.0χ2=0.01p=0.91h<0.01χ2=245.31p<0.001h=0.29EducationElementaryorHighSchool68021.830121.177393533.1χ2=0.26p=0.61h=0.02χ2=179.37p<0.001h=-0.25College118037.951836.394598040.5χ2=0.95p=0.33h=0.03χ2=8.87p<0.01h=-0.05University125040.160742.561620026.4χ2=2.30p=0.13h=-0.05χ2=301.14p<0.001h=0.29MaritalStatusSingle2287.31077.51090454.7χ2=0.03p=0.87h<-0.01χ2=48.38p<0.001h=0.11MarriedorCommonLaw254581.6117382.2203006086.9χ2=0.16p=0.68h=-0.01χ2=74.87p<0.001h=-0.14Separated/Divorced33910.914510.21970058.4χ2=0.45p=0.50h=0.02χ2=23.73p<0.001h=0.08EmploymentStatusWorkingfull-time206466.294366.1124509053.3χ2<0.01p=0.96h<0.01χ2=208.25p<0.001h=0.26Workingpart-time47015.121515.175358532.3χ2=0p=1h<0.01χ2=419.79p<0.001h=-0.41Notworking/Retired/Other57018.326418.533744514.4χ2=0.02p=0.90h<-0.01χ2=36.86p<0.001h=0.10HouseholdIncome(CAD$beforetaxes)$39999orless39512.717312.134494014.8χ2=0.22p=0.64h=0.02χ2=10.67p<0.001h=-0.06Perez et al. BMC Public Health  (2016) 16:1223 Page 7 of 17Table1Socio-demographicsforT1,T2andStatisticsCanadanationalhouseholdsurveysamples.TestofproportionsandeffectsizebetweenT1toT2andT1toStatisticsCanadasample(Continued)Time1n=3117Time2n=1427StatCann=2336115T1:T2EffectsizeCohen’shT1:StatCanEffectsizeCohen’shn%n%n%χ2valuepvalueχ2valuepvaluebetween$40000and$5999942813.718713.133265014.2χ2=0.28p=0.60h=0.02χ2=0.62p=0.43h=-0.01between$60000and$7999946815.022115.533800014.5χ2=0.14p=0.71h=-0.01χ2=0.71p=0.40h=0.02between$80000and$9999951116.423716.632393513.9χ2=0.02p=0.89h<-0.01χ2=16.44p<0.001h=0.07$100000ormore100932.445932.299659042.7χ2=0.01p=0.92h<0.01χ2=134.32p<0.001h=-0.21NationalityBorninCanada271787.2126388.5161747569.2χ2=1.50p=0.22h=-0.04χ2=469.17p<0.001h=0.44NotborninCanada39712.716411.571863530.8χ2=1.28p=0.26h=0.04χ2=474.22p<0.001h=-0.45EthnicityWhite(e.g.,Caucasian,European)274187.9128089.7168643572.2χ2=2.81p=0.09h=-0.06χ2=383.89p<0.001h=0.40EastAsian(e.g.,Chinese,Filipino,Japanese,Korean,Vietnamese)1193.8493.42032958.7χ2=0.30p=0.58h=0.02χ2=92.93p<0.001h=0.21OtherEthnicities2317.4845.944638519.1χ2=3.29p=0.07h=0.06χ2=274.96p<0.001h=-0.35ReligionChristian189860.988161.7157829567.6χ2=0.26p=0.61h=-0.02χ2=62.85p<0.001h=-0.14NoFaith98431.644431.148588520.8χ2=0.07p=0.79h<0.001χ2=218.42p<0.001h=0.25OtherFaiths1705.5745.227193511.6χ2=0.09p=0.76h=0.01χ2=115.30p<0.001h=-0.22StatCan=StatisticsCanada.T1:T2isthecomparisonbetweenTime1sampleandTime2sample.T1:StatCaniscomparisonbetweentheTime1sampleandStatisticsCanada’sNationalHouseholdSurvey(2011)samplePerez et al. BMC Public Health  (2016) 16:1223 Page 8 of 17coded) dispersed across 7 separate web pages in our onlinePerez et al. BMC Public Health  (2016) 16:1223 Page 9 of 17questionnaire. There were 13, 9, 7, 11, 8, 10 and 6 items acrossthe 7 different web pages. We flagged participants who had 0variance across the items on more than 4 of the 7 pages.For the validity criterion, we used three bogus itemsfrom Weinberger and colleagues [62]: “I have never metanyone younger than I am”; “Everyone makes mistakesat least once in a while”, and “I am answering thesequestions truthfully” with response options ranging from1= “strongly disagree” to 7 = “strongly agree”, where 4 =“neutral”. We reverse coded the first item and created a totalvalidity score for the three items. We removed participantswho scored 12 or below, then, re-introduced any participantwho answered “neutral” to all three items. The rationale forthis cut-off was that we sought to identify participants whoscored below “neutral” (somewhat disagree, disagree andstrongly disagree) given that the correct answer to these itemswas to “agree” with them (note that the opposite is true forthe one reverse coded item). We chose to re-introduce anyparticipant who answered “neutral” to all three items as theseitems are available for subjective interpretation and those whorecommended childhood vaccines. Parents were askedwho the primary health decision-maker was for their son(e.g., mother, father or joint).Lastly, parents were also asked about behaviors theyintended to complete at T1 (e.g., contact an HCP, searchthe internet), and at T2, using the computer-adaptivetesting, we re-assessed if the specified behaviors theyindicated at T1 were indeed carried out by T2.Other additional items include: if the participant have anydaughters and/or any vaccinated daughters (2 items);parent's health behaviours (3 items) communication aboutsex/HPV vaccination (7 items); degree of parental/soninvolvement in HPV vaccine decision-making (3 items),willingness to vaccinate at different price points (4 items);vaccine conspiracy beliefs (9 items) [59]; right wingauthoritarianism (7 items); beliefs about other parents whodo not vaccinate their child (2 items) and the ConspiracyMentality Questionnaire (5 items) [60] are found in theadditional file.Data cleaningAddressing careless/unmotivated respondersOnce data collection was completed, we sought to ensure thehighest level of data quality and integrity of our conclusions.We used four data cleaning methods to identify participantswho might not have used appropriate care while completingthe questionnaire i.e., careless or unmotivated responders [61].The four methods employed were: variance, bogus items,psychometric antonyms and psychometric synonyms [61]. Forthe variance criterion, we examined 64 items (some reversewere systematically answering “neutral” to all items would beremoved by the variance method.Another method used was psychometric synonymsand antonyms [61, 63], which are consistency indicesthat help to eliminate bias by examining differences initems that are highly similar or opposing in content. Weexamined any questionnaire item that had a 7-pointLikert response option. Post hoc, we standardized allrelevant items into z scores and correlated all items. Weidentified the 30 most positively and 30 most negativelycorrelated items. We recoded these items to create pairsof synonyms and then calculated the correlation betweensynonyms and antonyms for each participant, whichestablished a synonym index and an antonym index foreach participant. We then flagged all values less than -2standard deviations (SD) on the synonyms index andgreater than +2 SD on the antonyms index as thesecorrelations could be seen as extreme outliers.These four methods identified that 15% of our sampleat T1 (n = 575) and 5% of our sample (n = 202) at T2belonged to a latent class that can be considered carelessor unmotivated in their responses, a percentage nearlyidentical to findings by other research groups [61, 64].Data collected from these participants were removedfrom our final sample (see Fig. 1).Self-report of son’s vaccination statusFollowing T1 data collection, we inspected the data fromour primary outcome variable, PAPM stage. The authorsobserved that some participants’ responses were im-plausible, nonsensical or inaccurate. We speculated thatperhaps parents may have confused the HPV vaccinewith other childhood vaccinations, and therefore someparticipants likely did not match the profile of a partici-pant who had truly vaccinated his or her son againstHPV. For example, some participants indicated thattheir son had been vaccinated in school, even thoughthey lived in provinces where indeed no school-basedprograms for boys yet existed. This challenge of self-re-port (i.e., subjective) vaccination as opposed to objective(e.g., vaccination booklet with official stamps or elec-tronic vaccination registries) has been reported in theliterature [65, 66].During data cleaning at T1, the authors thereforeestablished a first method of examining a set of 10criteria to increase the likelihood that parents who hadindicated that they had vaccinated their son were notfalse positives. Furthermore, in order to improve uponthe accuracy of parents’ self-reported vaccination status,at T2, we prompted those who selected PAPM stage 6(i.e., vaccination) with a brief informative statementabout the Canadian HPV vaccine policy (e.g., we in-formed participants that except for PEI, parents have topay/purchase the HPV vaccine) and then asked thePAPM stage item a second time to ensure that theirPAPM stage was as accurate as possible.differences on all socio-demographic variables exceptPAPM stagesThe number and percentage of parents across the sixPAPM stages is presented in Table 2. The HPV vaccinationuptake of Canadian males 9-16 years old was very low, withonly 34 and 39 parents reporting that their sons were vacci-nated at T1 and T2, which represents an HPV vaccine up-take rate of 1.1% at T1 and 2.7% at T2. Of the few parentswho indicated that they had vaccinated their son, 47% re-ceived one dose at T1 and 56% at T2 (p > 0.05). Two orthree doses were reportedly received by 53% of sons at T1and 44% at T2 (χ2 = 0.32, CI: -0.34; 0.16, p > 0.05).While there was a free school-based program in placefor boys in Grade 6 in PEI, our results still show that 19parents from PEI were unaware, unengaged or un-decided. At T2, there was a program in place for boys inPerez et al. BMC Public Health  (2016) 16:1223 Page 10 of 17for two provinces and language (see Table 1). We hadsignificantly more respondents from Quebec and fewerrespondents from Saskatchewan at T2 compared to T1but the difference was small (h ≤ 0.2). We also hadfewer English respondents and more French respon-dents at T2 compared to T1, and the difference wassmall as well (h ≤ 0.2).A comparison of the T1 and Statistics Canada sam-ples revealed that there were statistically significantdifferences for the proportions of responses betweenthe two samples for all provinces (except Alberta,Manitoba and Saskatchewan), language (except bilin-guals), gender, education, marital status, employmentstatus, income (except those earning between $40 000and $59 999 and those earning between $60 000 and$79 999), nationality, ethnicity and religion (see Table 1).An examination of the effect size indicates that theeffect size was small for 14 differences and medium forAt T2, two additional issues arose. The first issue wasimpossible PAPM stage transitions. From both a theoret-ical and practical perspective, it is impossible for some-one to report being in stages 2–6 at T1, and then toreport being in stage 1 at T2. For such a report to betrue, the participant would need to have become un-aware, after having previously been aware that the HPVvaccine could be administered to males. The secondissue was the impossibility of someone moving fromreporting that their son had been vaccinated (Stage 6) atT1, to then reporting any other stage at T2 (i.e. implyingthat their son is no longer vaccinated). In total, usingthe aforementioned three methods, 92 participants wereremoved from the final sample due to likely inaccurateor implausible vaccination stage (see Fig. 1).Statistical analysis was conducted using SPSS v23and R v3.2.2.ResultsThe mean time to complete the questionnaire was 21 minat T1 and 24 min at T2.Participants and socio-demographicsThe final cohort consisted of 3,117 participants at T1 and1,427 at T2, representing a 45% attrition rate (see Fig. 1for recruitment overview). The response rate, calculatedbased on completion by participants who initiated thequestionnaire (n = 5733 at T1 and n = 1999 at T2), was66.0% at T1 and 80.4% at T2. The sample’s socio-demographic characteristics are presented in Table 1.When comparing the T1 and T2 samples, the sampleswere found to be similar as there were no significant18 differences (see Table 1). In no case, was the effectsize large (see Table 1).Grade 5 in Alberta, and our results indicate that 85parents were unaware, unengaged or undecided fromthese two provinces. Moreover, at T1, only 1 parentfrom the 34 (2.9%) who reported their son was vacci-nated were from provinces offering free HPV vaccinationfor boys (PEI) and at T2, 11 from the 39 (28.2%) wereparents of vaccinated sons who were from provinces thatwere vaccinating boys against HPV as part of the provin-cial immunization schedule (PEI and Alberta).HPV and HPV vaccine knowledgeWe validated and extended Waller et al.’s existingknowledge scales and create a 25-item HPV generalknowledge scale and the 11-item HPV vaccine know-ledge scale, which were found to be psychometricallyrobust [67].The mean scores for HPV knowledge were 11.67 (from25 possible points) at T1 and 14.02 at T2 (t = 12.11, CI:1.97; 2.73, p < 0.01). The mean scores for HPVvaccination knowledge were 5.22 (from 11 possible points)at T1 and 6.3 at T2 (t = 12.27, CI: 0.9; 1.24, p < 0.01).Table 2 PAPM stages at Time 1 and Time 2PAPM Stage Time 1 Time 2n % n %I was unaware that the HPV vaccine could begiven to males (Stage 1)1778 57.0 218 15.3I was aware that the HPV vaccine can be givento males, but I have not thought about gettingthe HPV vaccine for my son (unengaged, Stage 2)652 20.9 462 32.4I have thought about getting the HPV vaccinefor my son, but I am undecided about gettingthe HPV vaccine for him (Stage 3)284 9.1 360 25.2I have decided I do NOT want my son to getthe HPV vaccine (Stage 4, decided not to)212 6.8 208 14.6I have decided I DO want my son to get theHPV vaccine (Stage5, decided to)157 5.0 140 9.8My son has already received the HPV vaccine(Stage 6, vaccinated)34 1.1 39 2.7A detailed elaboration of these results (e.g., what parentsknow/don’t know) and the relationship between know-ledge and PAPM stages are presented elsewhere [67].Attitudes and beliefsWe developed and validated a comprehensive,psychometrically-sound HPV vaccination attitudesand belief scale (HABS), which contains 46 itemsand 9 factors: benefits, threat, influence, harms, risk,affordability, communication, accessibility and generalattitudes (see Additional file 1). The psychometric proper-ties of the scale are described in another paper [68].Information sourcesMost parents (94% at T1 and 88% at T2) never spokewith a doctor /HCP about the HPV vaccine for their son(χ2 = 40.4, CI: 0.04; 0.08 p < 0.01, h = 0.2).Of the few parents (6% at T1 and 11.4% at T2) who didHealth behaviorsAt both time points, parents indicated that their son’shealthcare decisions are typically a joint decision madeby both parents (60.4% at T1 and 62% at T2, χ2 = 0.5,p > 0.05), followed by mothers alone (40.2% at T1 and39% at T2, χ2 = 1.05, p > 0.05) and fathers alone (5% at T1and 4.6% at T2, χ2 = 0.28 p > 0.05).More than half of parents (61% at T1 and 59% at T2)mentioned that their son underwent a routine checkupwith a healthcare provider in the previous year (χ2 = 2.07,CI: -0.008; 0.054, p > 0.05). Most parents (93% at both T1and T2) stated that their sons have received all childhoodvaccines. Interestingly, at T1 and T2 respectively, 25.5%and 21.2% of parents who decided not to vaccinate theirson against HPV stated their son did not receive all recom-mended childhood vaccines; the proportions were signifi-cantly higher than parents belonging to any of the other 5PAPM stages at both time-points (p < 0.05).Perez et al. BMC Public Health  (2016) 16:1223 Page 11 of 17speak to their doctors/HCP, 59% of them were recom-mended to get the HPV vaccine for their son at T1 and69% at T2 (χ2 = 3.33, CI: -0.21; 0.006, p = 0.07). At T1,55.8% of those parents who vaccinated their son hadspoken with a HCP about the HPV vaccine. More thanhalf the sample (54%) at both T1 and T2 prefer to receivetheir information from an HCP, which was by far themost preferred source of information, followed bypublic health brochures, pamphlets, flyers or posterswhich was reported by 18% of parents at T1 and T2.Parents reported that the sources from which theyactually received information about the HPV vaccine(e.g., TV or radio) did not correspond with their mostpreferred information source (e.g., from their HCP,see Fig. 2).Fig. 2 Percentage of participant’s actual source of receiving HPV vaccine inTime 1 and Time 2Implementation intentionsIn most cases, parents did not implement their planned/intended actions to facilitate HPV vaccination between T1and T2. Parents increased the search for information aboutHPV vaccine in written sources (i.e., brochures, books,magazines) at T2 (21%) compared to T1 (15%) (see Fig. 3).Some parents did not name a planned intention, but whenthey stated nothing, they indeed remained in status quo.Stage transitions from T1 to T2 (n = 1427)We had 539 (37.7%) participants who remained in thesame stages of vaccination adoption (i.e., PAPM stage)from T1 to T2; this includes 3 participants who indi-cated at T1 that their sons were vaccinated. A higherformation compared to their preferred information sources at both1 cPerez et al. BMC Public Health  (2016) 16:1223 Page 12 of 17Fig. 3 Percentage of participant’s self-reported planned actions at Timenumber, 705 (49.4%) progressed from T1 to T2 towardsadvanced PAPM stages that are closer to action i.e.,vaccination; 53 participants (3.7%) regressed (to earlierstages than they initially were in, away from action); only36 parents (2.5%) advanced to having their sonsvaccinated at T2. Of the 1238 participants who initiallyidentified as being unaware, unengaged or undecidedat T1 and who completed the T2 questionnaire, 27progressed to vaccinated at T2. Of the 80 participantswho had decided to act at T1 and who completed the T2questionnaire, only 9 participants (11%) progressed tobeing vaccinated at T2. Not a single participant in stage 4in T1 (i.e. decided not to act, n = 106) moved towardsdecided to act or vaccination at T2. 130 participants(9.1%) moved from unaware, unengaged, undecided ordecided to act at T1 to decided not to act at T2 (see Fig. 4).DiscussionTo our knowledge, this is the first HPV vaccinationspecific survey in a pan-Canadian representative sampleof parents of boys after the first HPV vaccine (Gardasil®)was licensed in Canada for males in September 2010[14]. Other vaccination surveys such as the ChildhoodNational Immunization Coverage Survey (CNICS) con-ducted by Statistics Canada have not been gender andHPV specific [69], such that the data collected are lessrepresentative of the Canadian population of parents ofIntentions)ompared to actions reported as completed at Time 2 (Implementationboys and do include items about HPV vaccination formales. At the time of data collection, only one of the tenprovinces at T1 (PEI), and two of the provinces at T2(PEI and Alberta) had implemented school-based HPVvaccination program for males, and no territories offeredschool-based HPV vaccination for boys. As such, only asmall number of parents from PEI and Alberta and (i.e.,only those with sons in grade 6 and 5 respectively) wereeligible for free school-based HPV vaccination programs.In the absence of programs, the HPV vaccine uptake,was exceptionally low at both T1 (1.1%, n = 34 from3117) and T2 (2.7%, n = 39 from 1427).Similarly, the lack of programs for boys, and in turnthe cost of vaccinations as well the lack of information(e.g., not even knowing boys can get the HPV vaccine;lack of understanding about the benefits/risks; no rec-ommendation from a HCP) likely explains why at bothtime-points most parents (87% at T1 and 73% at T2)were in the first three stages of adoption (unaware, un-engaged or undecided). Furthermore, post-hoc, we ex-amined the few sons (n = 34 and T1 and n = 39 at T2)who were vaccinated, and the majority was not evenfrom provinces that offered free-school based HPVvaccination programs. Having two provinces that hadintroduced male HPV vaccination programs did not ap-pear to skew our ‘snapshot’ of parental HPV vaccinedecision. We were also able to establish a reliablen ox-aPerez et al. BMC Public Health  (2016) 16:1223 Page 13 of 17estimate of HPV vaccine uptake in Canada. Currently(as of September 2016), there are six Canadian provincesFig. 4 Number of participant’s initial PAPM stage reported at T1 is showstage or their movement to a different PAPM stage at T2 shown on thewith HPV vaccination programs for males. The six Can-adian provinces join only a handful of other countries/regions e.g., Australia, Austria, Israel, Barbados, Lichten-stein, New Zealand that have implemented or are set toimplement publicly funded HPV vaccination programsfor boys [25, 29, 30]. Our work offers valuable baselineinformation to all stakeholders involved in implementingand evaluating HPV vaccination programs.At T2, almost half the sample moved forward along thePAPM vaccine decision-making trajectory, with mostmoving towards unengaged or undecided. Over a third ofthe sample remained in the same stage as at baseline.These results are not surprising, considering our studywas an observation design and not an intervention study.Moreover, the movement towards the later stages of adop-tion was minimal, i.e., very few parents moved towardsdeciding to act and acting/vaccination. In the absence ofprograms or targeted interventions that match parents’informational needs, most parents remained fixed in theircurrent and/or earlier stages of adoption. The forwardmovement along the PAPM vaccine decision-makingtrajectory could likely be explained by parents acquiringinformation through written sources (e.g., media) orsimply by virtue of completing the questionnaire at T1.Furthermore, voluntary initiation of parents e.g. toacquire information via the internet or to speak totheir HCP was not found at T2. Of those parentswho had decided to vaccinate their son at T1 i.e., hadintentions and who completed the T2 questionnaire,n the y-axis. Number of participant’s who remained in the same PAPMxis (n =1427)very few parents followed through in vaccinating theirsons even when they were in the later stages ofdecision-making. This finding supports a growingbody of research showing that there are importantgaps between intending to act and carrying out inten-tions [70]. Therefore, some individuals likely requirehelp developing specific implementation plans to re-duce the barriers.Of interest, the most immobile group were thosewho had decided not to vaccinate, with no parent inthis stage (of 106) moving toward intentions orvaccination at T2. Our results complement previousresearch suggesting that a proportion of these parentsmay likely be hesitant towards all vaccines and notuniquely against the HPV vaccine, and perhaps moreakin to what are known as “anti-vaxxers” [71, 72].For the entire sample, HPV knowledge and HPVvaccine knowledge remained poor at both time-points. The relationship between parent’s knowledgeand vaccine acceptance/intentions is mixed andequivocal [73–77]. Low knowledge in the presentgroup of parents could be explained by the relativelynew recommendation of the HPV vaccine for boysand indicate the need to inform parents about thelink between HPV and penile, anal and oral cancersas well as GW. Importantly, there were discrepanciesbetween preferred and actual HPV informationPerez et al. BMC Public Health  (2016) 16:1223 Page 14 of 17channels. Although parents are requesting and requir-ing more information on HPV vaccination, theirneeds are not being met. Providing relevant, accurateinformation about the recommendation and benefitsof the HPV vaccine for boys, ideally delivered by adoctor or HCP, could improve HPV vaccine uptake.Our results also indicated that the vast majority ofCanadian parents have not received a recommendationfrom their HCP about the HPV vaccine for their sonsdespite their HCP being the primary source they preferand want to receive information from. Moreover, whilethe sample size is small (n =36), 80% of parents who ad-vanced towards actual vaccination from T1 to T2 re-ceived a recommendation from their HCP. An HCPrecommendation has almost consistently been shown tobe associated with increased parental HPV vaccine accept-ability [73, 76, 78–80] and the absence of an HCP recom-mendation has been associated with negative attitudesand refusal of HPV vaccination [74–76, 80]. Facilitatingknowledge translation through HCPs should be a majorgoal for future interventions to increase HPV knowledgeand in turn, improve HPV vaccination uptake [14]. Otherpotential avenues where parents could acquire HPV infor-mation is from public health brochures, pamphlets andposters provided by government health organizations andendorsed by different medical organizations (e.g. CanadianMedical Association) which may be seen as an HCP en-dorsement. Since other vaccines (e.g., Tdap, Hepatitis Band meningococcal) are given to Canadian children at asimilar age/grade as the HPV vaccine, an opportunity ex-ists to pair the vaccines together in administration andeducate parents about HPV vaccination.The present study’s strengths are related to the study’slongitudinal design, data collection tool (questionnaire),data collection method (online survey to acquire a pan-Canadian sample) and data cleaning techniques. The on-line survey approach allowed us to: 1) use computer-adaptive testing, 2) avoid missing data, and 3) collectdata in a time efficient way. Furthermore, by developinga strong data-cleaning algorithm, we increased the reli-ability of our final data. Moreover, the authors engagedin extensive psychometric testing [67, 68] to ensure thevalidity of the psychosocial constructs which has beenrecommended in this area of research [33]. Additionally,our study utilized a longitudinal design, which will allowus to analyze how the psychosocial determinants influ-ence HPV vaccine decision making over time. To thebest of our knowledge, there is only one existing lon-gitudinal study of parents of boys which was con-ducted outside of Canada [81]. Moreover, our resultsconfirmed that intentions do not translate into vac-cination over time (only 7/80 of the decided to whenon to vaccinate their sons), which is often unknownin most intention studies. Lastly, the use of thePAPM allowed us to capture HPV vaccine decision-making in a more nuanced way, and not presumethat all parents are aware or engaged in this particu-lar health behavior. Therefore, our results demon-strate that in studying HPV decision-making, thePAPM is likely a fitting theoretical model in contrastto the HBM or IBM, which ignore the earlier stagesof vaccine decision-making.Our study is limited in several ways. Compared to datacollected from Statistics Canada household survey sam-ple of parents with 9-16-year-old, there were differencesin the structure of our sample. The effect size wasmostly small to medium with no effect size exceeding0.6. In our opinion, the small to medium differencesallow us to generalize our results to the Canadian con-text. Our suggestion for future studies would be to im-pose quotas based on the repartition of respondentsconsistently with national representative available data inorder to further reduce sample differences. Additionally,our sample consisted of more mothers (65%) thanfathers (35%). Importantly, our response rate of males ishigher than in other studies reporting HPV vaccinerelated attitudes where the average proportion ofmothers was 82.3% [37]. Therefore, in our opinion theproportion of males and females in our sample closelyreflects the gender specific HPV vaccination decision-making process in Canada. Participants were also lost tofollow-up, but importantly our T2 sample was comparableand nearly identical to the original T1 sample on all socio-demographic variables albeit province and language,where the effect was small. Moreover, we were unable tosample the three Northern territories constituting ofmostly Indigenous peoples (e.g., North American Indian,Inuit), as these residents were not represented in Leger’spanel. Future research should evaluate the psychosocialdeterminants of HPV vaccine decision-making in thispopulation. Additionally, the present findings did notanalyze the confounding role of having daughters who areeligible for HPV vaccination in the household. Futureanalyses are underway which will examine whether havinga vaccinated daughter is a predictor of PAPM stage. Afinal limitation was the recall bias of some participants’self-reported vaccination status. The issue of inaccurateself-report of vaccination as opposed to actual (e.g. vaccin-ation booklet, physician’s record) has been reported in thevaccine literature [65]. In the absence of an HPVimmunization school-based program, most males re-ceive the HPV vaccine privately and the option toregister this information with national databases isvoluntary. As the HPV vaccination rate was extremelylow (1-3%) in our study, and the HPV vaccine wasnot included in provincial immunization programs,we have reason to believe that the lack of objectiveproof of vaccination had only a small influence onPerez et al. BMC Public Health  (2016) 16:1223 Page 15 of 17our results. Future studies should consider that par-ents’ self-reported vaccinated status may be unreliableand should try to use objective records to preciselymeasure HPV vaccine uptake.ConclusionsOur results illustrate the exceptionally low uptake of theHPV vaccine in Canadian boys in the absence of a fundedimmunization program. Parents are critical to a successfulHPV vaccination program in children. Directing ourattention to males as much as females is importantbecause males play a role in transmission and arevulnerable to HPV-associated diseases. This data can helpdirect efforts towards helping Canadians become awarethat males are recommended to get the HPV vaccine andbe engaged in the decision to vaccinate their sons.Moreover, intentions to vaccinate one’s son orplanning to speak to one’s HCP did not translate intoaction for most parents over the 9-month follow-up.These results have implications for implementation ofstrategies (e.g., HCPs offering the HPV vaccine to theparent of a son directly and immediately during aroutine visit, fostering resources within schools toincrease HPV vaccine uptake). Lastly, the use ofstaged-based health behavior model, i.e., the PAPM,allowed for more precision as to where parents stoodalong the HPV vaccine decision-making trajectory.Forthcoming analyses to better understand the psy-chosocial determinants that influence each specificstage will allow us to target the unique gaps andbarriers of each PAPM stage.Endnotes1The PAPM original model consist of seven stages ofhealth decision-making. The seventh stage is a mainten-ance stage and does not apply to HPV vaccination. Forsimplicity, only the six stages are described.2Leger has the largest representative panel in Canadaand the largest Franco-Canadian panel. Since membersare recruited randomly over the phone, the Leger Panelis highly representative and offers exceptional qualityrespondents. Leger sampling process is based on datafrom Statistics Canada (e.g., province, age, gender,language and region).3As the questionnaire was computer adapted, fewitems were asked of only some groups. For example,only those participants who indicated they vaccinatedtheir son, were further asked about how many doseshe received.4The informative statement read as follows: Pleaseread carefully the following information about HPV.The Human Papillomavirus (HPV) is the most com-mon sexually transmitted infection. HPV can causegenital warts. HPV can also cause cancers of thecervix, penis, anus, vagina, vulva and oral cancers.There are HPV vaccines available that are sometimesreferred to as the cervical cancer vaccine, Gardasil®, orCervarix®. The HPV vaccine is given in 2 or 3 doses andcosts approximately $150–$200 per dose. Health Canadahas approved and recommended an HPV vaccine for bothmales aged 9–26 years and females aged 9–45 years.Additional fileAdditional file 1: Questionnaire Sections with variable constructs,number of items, sample items and response choices. (DOCX 142 kb)AbbreviationsBC: British Columbia; CNICS: Childhood National immunization coveragesurvey; GW: Genital warts; HABS: HPV Attitudes and Beliefs Scale; HBM: Healthbelief model; HCP: Healthcare provider; HPV: Human papillomavirus;IBM: Integrated behavioral model; MSM: Men having sex with men;NACI: Canada’s National advisory committee on immunization;PAPM: Precaution adoption process model; PEI: Prince Edward IslandAcknowledgementsThe authors warmly thank Dr. Eduardo Franco O.C. for his guidance andexpertise. The authors further extend thanks to Christopher A. Brown, KevenJoyal-Desmarais, Leonora King, Shelly Ann McNeil and Anila Naz for theirtime and support.FundingThis study was supported by: Grant #288295 from the Canadian Institute ofHealth Research (CIHR).Availability of data and materialsEntire questionnaire is available by contacting the authors. Data is availablein SPSS and Excel, and can be readily made available by contacting theauthors.Authors’ contributionsSP conceived and designed the study; performed the statistical analysis,interpreted the data and drafted the manuscript. OT performed the statisticalanalysis, interpreted the data and assisted in drafting the manuscript. GSassisted in data interpretation and provided critical feedback on manuscriptrevisions. ED, GO, JG, VG participated in study design and conceptualization,and provided critical feedback on manuscript revisions. ZR conceived anddesigned the study; assisted in data interpretation, provided critical feedbackon manuscript revisions. All authors read and approved the final manuscript.Competing interestsZR reports personal fees from Merck outside the submitted work at a consultationmeeting in November, 2015; and speaker to family physicians in April, 2015.Consent for publicationNot applicable.Ethics approval and consent to participateThe study was approved by the Institutional Review Board at the JewishGeneral Hospital in Montreal, Canada. Study participants consented toLeger’s terms of use and privacy policy, which covers that their data will beused anonymously for research studies.Author details1Department of Psychology, McGill University, 1205 Dr. Penfield Avenue,Montreal, QC H3A 1B1, Canada. 2Lady Davis Institute for Medical Research,Jewish General Hospital, 4333 Cote Ste-Catherine Road Room 214, Montreal,QC H3T 1E4, Canada. 3Institut National de Santé Publique du Québec, 2400D’Estimauville, Quebec G1E 7G9, Canada. 4Faculty of Medicine, University ofBritish Columbia, BC Women’s Hospital and Health Centre, Room H203G,Perez et al. BMC Public Health  (2016) 16:1223 Page 16 of 174500 Oak Street, Vancouver, BC V6H 3N1, Canada. 5Community HealthSciences, Faculty of Medicine, University of Calgary, 3280 Hospital Drive N.W,Calgary, AB T2N 4N1, Canada. 6Louise Granofsky-Psychosocial OncologyProgram, Segal Cancer Center, Jewish General Hospital, 4333 CoteSte-Catherine Road, Montreal, QC H3T1E4, Canada.Received: 11 June 2016 Accepted: 8 November 2016References1. Chaturvedi AK. Beyond cervical cancer: burden of other HPV-related cancersamong men and women. J Adolesc Health. 2010;46(4 Suppl):S20–6.doi:10.1016/j.jadohealth.2010.01.016.2. Public Health Agency of Canada. Update On Human Papillomavirus (HPV) Vaccines[Internet]. 2012 [cited 2016 May 5]. Available from: http://www.phac-aspc.gc.ca/publicat/ccdr-rmtc/12vol38/acs-dcc-1/index-eng.php. Accessed 11 Nov 2016.3. Forman D, de Martel C, Lacey CJ, Soerjomataram I, Lortet-Tieulent J, Bruni L,et al. Global burden of human papillomavirus and related diseases. 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