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UBC Theses and Dissertations

Evaluation of pertussis immunization during pregnancy Abu Raya, Bahaa


Pertussis disease is most severe among young infants, leading to high morbidity and mortality. To reduce the burden of pertussis disease among young infants, immunization against pertussis during pregnancy has been implemented in an increasing number of countries over the past decade. My research goals have focused on addressing important knowledge gaps in the field of pertussis immunization during pregnancy to inform an evidence-based immunization program. Using data on hospitalized pertussis cases admitted to pediatric tertiary care centers in Canada, I report that the highest morbidity and mortality from pertussis is among infants <2 months of age with an incidence rate of 116.4/100,000/year, 38% intensive-care unit admission rate, and 2.3% case fatality rate. Age <16 weeks, encephalopathy and prematurity were independently associated with a 5-fold, 21-fold and 6-fold increased risk for intensive-care unit admission, respectively. I also developed a novel approach that enables comprehensive characterization of anti-pertussis immunoglobulin G (IgG) avidity using a range of bond-breaking agent concentrations combined with high-dimensional biology statistical tools. I applied this approach on cord blood samples, and found that vaccination against pertussis during pregnancy was associated with high levels of high-avidity antibodies. I also found that maternal pertussis vaccination at 28–32 weeks gestation was associated with higher cord blood anti-pertussis IgG avidity that vaccination at 33–36 weeks gestation. Furthermore, I compared antibody responses after primary and/or booster immunization in infants born to women with and without pertussis immunization during pregnancy. I found lower vaccine-induced antibody responses to pertussis, diphtheria and some Streptococcus pneumoniae serotypes in infants born to women vaccinated against pertussis during pregnancy compared with infants of unvaccinated women. The body of work presented here assists public health policy makers to reach evidence-based recommendations across countries. Supporting earlier immunization in the 3rd trimester will be of particular clinical relevance for preterm infants who would completely miss out on protection via maternal antibodies if immunization only occurred in late pregnancy. These data from the meta-analysis supports enhanced surveillance of pertussis, diphtheria and invasive pneumococcal disease in infants to determine the clinical significance of this effect.

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