RT Journal Article SR Electronic T1 Effectiveness of pertussis vaccination and duration of immunity JF Canadian Medical Association Journal JO CMAJ FD Canadian Medical Association SP E399 OP E406 DO 10.1503/cmaj.160193 VO 188 IS 16 A1 Kevin L. Schwartz A1 Jeffrey C. Kwong A1 Shelley L. Deeks A1 Michael A. Campitelli A1 Frances B. Jamieson A1 Alex Marchand-Austin A1 Therese A. Stukel A1 Laura Rosella A1 Nick Daneman A1 Shelly Bolotin A1 Steven J. Drews A1 Heather Rilkoff A1 Natasha S. Crowcroft YR 2016 UL http://www.cmaj.ca/content/188/16/E399.abstract AB Background: A resurgence of pertussis cases among both vaccinated and unvaccinated people raises questions about vaccine effectiveness over time. Our objective was to study the effectiveness of the pertussis vaccine and characterize the effect of waning immunity and whole-cell vaccine priming.Methods: We used the test-negative design, a nested case–control study with test-negative individuals as controls. We constructed multivariable logistic regression models to estimate odds ratios (ORs). Vaccine effectiveness was calculated as (1 – OR) × 100. We assessed waning immunity by calculating the odds of developing pertussis per year since last vaccination and evaluated the relative effectiveness of priming with acellular versus whole-cell vaccine.Results: Between Dec. 7, 2009, and Mar. 31, 2013, data on 5867 individuals (486 test-positive cases and 5381 test-negative controls) were available for analysis. Adjusted vaccine effectiveness was 80% (95% confidence interval [CI] 71% to 86%) at 15–364 days, 84% (95% CI 77% to 89%) at 1–3 years, 62% (95% CI 42% to 75%) at 4–7 years and 41% (95% CI 0% to 66%) at 8 or more years since last vaccination. We observed waning immunity with the acellular vaccine, with an adjusted OR for pertussis infection of 1.27 (95% CI 1.20 to 1.34) per year since last vaccination. Acellular, versus whole-cell, vaccine priming was associated with an increased odds of pertussis (adjusted OR 2.15, 95% CI 1.30 to 3.57).Interpretation: We observed high early effectiveness of the pertussis vaccine that rapidly declined as time since last vaccination surpassed 4 years, particularly with acellular vaccine priming. Considering whole-cell vaccine priming and/or boosters in pregnancy to optimize pertussis control may be prudent.