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Background: Pertussis remains poorly controlled relative to other diseases targeted by childhood vaccination programs. We combined estimates from four population-based studies of pertussis vaccine effectiveness (VE) in three Canadian provinces using a meta-analytic approach to improve precision and explore regional variation in VE and durability of protection., Methods: Studies were conducted in Alberta, Manitoba, and Ontario over periods ranging from 1996 to 2015. Adjusted log odds ratios (OR; VE = 100*[1-OR]) of the effect of vaccination on pertussis risk were estimated by time since last vaccination in each study and pooled using DerSimonian and Laird random-effects models. We used the I 2 statistic to estimate between-study heterogeneity and assessed methodological and clinical heterogeneity through subgroup analyses of study design and age., Results: Data on 3,270 pertussis cases and 23,863 controls were available. Pertussis VE declined from 86% (95% CI 79%-90%, I 2  = 81.5%) at < 1 year since last vaccination to 51% (11%-74%, I 2  = 80.9%) by ≥ 8 years. Effect estimates were the most heterogeneous in the least and most elapsed time periods since last vaccine dose. This was attributable mostly to variation between provinces in the distribution of age groups and number of vaccine doses received within time periods, as well as study design and small numbers in the most elapsed time period., Interpretation: Consistent trends of decreasing pertussis VE with increasing time since last vaccination across three Canadian provinces indicate the need for immunization schedules and vaccine development to optimize protection for all individuals, especially for adolescents and young adults at greatest risk of infection., Competing Interests: Declaration of Competing Interest The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: CHR has received an unrestricted research grant from Pfizer for an unrelated study. SMM has received unrestricted research grants from Merck, GlaxoSmithKline, Sanofi Pasteur, Pfizer and Roche-Assurex for unrelated studies, as well as fees as an advisory board member for Sanofi Pasteur., (Crown Copyright © 2021. Published by Elsevier Ltd. All rights reserved.)

Background: Pertussis is still frequently reported in Canada. In Alberta, pertussis incidence ranged from 1.8 to 20.5 cases per 100,000 persons for 2004-2015. Most cases occurred in those aged <15 years. In Alberta, acellular formulations replaced whole-cell in 1997. We investigated pertussis vaccine effectiveness (VE) using a test-negative design (TND) study., Methods: We included all persons who had a real-time PCR laboratory test for Bordetella pertussis between January 1, 2010 and August 31, 2015, in the province of Alberta, Canada. Vaccination history was obtained from Alberta's immunization repository. Vaccination status was classified as complete, incomplete, or unvaccinated, based on the province's vaccination schedule. Persons who had received ≥one dose of whole cell vaccine were excluded from analysis. Multivariable logistic regression models were used to estimate adjusted odds ratios (aOR) and 95% confidence intervals (95% CI) for pertussis infection by time since last vaccination. We adjusted for vaccination status, age, sex, neighbourhood income, urban/rural status, and the presence of a co-morbid condition. VE was calculated as [(1 - aOR) * 100]., Results: Of the 12,149 tests available, 936 (7.7%) were positive for Bordetella pertussis. Among the full cohort, VE was 90% (95% CI 87-92%) at 1 year, 81% (95% CI 77-85%) at 1-3 years, 76% (95% CI 68-82%) at 4-7 years, and 37% (95% CI 11-56%) at 8 or more years since a last dose of acellular pertussis vaccine., Conclusions: Pertussis VE was highest in the first year after vaccination, then declined noticeably as years since a last vaccination increased. Our results suggest that a large number of adolescents and adults are susceptible to infection with Bordetella pertussis. Regular boosters throughout childhood, adolescence, and during pregnancy may be needed., (Copyright © 2019 Elsevier Ltd. All rights reserved.)

Objective: To assess vaccine coverage for a cohort of children who have been in the care of the child welfare system compared to children in the general population., Methods: This retrospective cohort study used population-based administrative health data for a 2008 birth cohort of children from Alberta, Canada. We assessed coverage at ages 2 (n = 44,206) and 7 (n = 42,241) for three vaccines with different administration schedules for children in care (at any period before the age of assessment) and those who had never been in care, comparing them using risk differences and relative risks (RRs). We similarly assessed coverage for children not in care who shared characteristics of children in care., Results: At age two, vaccination coverage for children in care ranged from 54.3% to 81.4%, depending on vaccine. In comparison, coverage for those not in care ranged from 74.2% to 87.4%. At age seven, coverage for children in care ranged from 53.1% to 65.3%, compared to 76.6% to 83.4% for those not in care. For all vaccines at both ages, the risk for being under-vaccinated was higher for children in care (e.g., diphtheria, pertussis, tetanus, polio, Haemophilus influenzae type b at age 7: RR 2.01, 95% confidence interval [CI] (1.74-2.32). Even for children not in care who had characteristics similar to children in care, we found children in care had lower coverage., Conclusion: Children in care have consistently lower vaccine coverage than children not in care. Policies and practices should promote optimal access to vaccination for these children.

Introduction: Vaccination status is often categorized as complete or not-complete. This ignores the potentially important heterogeneity in children whose vaccinations are not-complete. We sought to subcategorize not-completely vaccinated children and determine whether characteristics differed among these subgroups., Methods: This retrospective cohort study assessed vaccination status at 2 years of age for 43,965 children in the 2008 Alberta (Canada) birth cohort who were registered with provincial vital statistics records. Children were categorized (based on the five routinely scheduled childhood vaccines) as complete, incomplete, selective, or non-vaccination status. Characteristics derived from administrative health databases were used to determine factors associated with vaccination status., Results: Population-level vaccination status at 2 years of age was found to be: 71.1% complete and 28.9% not complete (21.9% incomplete, 2.0% selective, and 5.1% non-vaccinated). Midwife delivery at home, compared to physician delivery in hospital, was strongly associated with non-vaccination status (adjusted odds ratio [aOR] 51.70, 95% CI 37.10-72.10). Factors that might pose barriers to vaccination, such as single marital status (aOR 1.58, 95% CI 1.49-1.67), large number of household children (≥4 vs. 1) (aOR 3.24, 95% CI 2.95-3.54), and multiple household moves (≥3 vs. 0) (aOR 1.69, 95% CI 1.35-2.10), were all strongly associated with incomplete vaccination status., Conclusions: Of the children who were not completely vaccinated at age 2, the vast majority had started but not completed the vaccination series, while a smaller number were selectively vaccinated or not vaccinated at all. Distinct differences are present among these groups that require attention when addressing vaccine coverage., (Copyright © 2015 Elsevier Ltd. All rights reserved.)