Trends and characteristics of Tdap vaccination during pregnancy in Ontario, Canada: a retrospective cohort study.

Background: In February 2018, Canada's National Advisory Committee on Immunization (NACI) recommended tetanus toxoid, reduced diphtheria toxoid and acellular pertussis (Tdap) vaccination during pregnancy to protect newborns against pertussis infection. We sought to describe pre- and postrecommendation trends in Tdap vaccination coverage among pregnant Ontario residents.
Methods: Using linked health administrative databases, we conducted a population-based retrospective cohort study of all pregnant individuals who gave birth in Ontario hospitals between April 2012 and March 2020. We described Tdap vaccination patterns in pregnancy for the entire study period and before and after the NACI recommendation. We used log-binomial regression to identify characteristics associated with Tdap vaccination during pregnancy.
Results: Among the 991 850 deliveries included, 7.0% of pregnant individuals received the Tdap vaccination during pregnancy. Vaccine coverage increased from 0.4% in 2011/12 to 29.2% in 2019/20. Coverage was highest among individuals who were older, had no previous live births, had adequate prenatal care and received maternity care primarily from a family physician. After adjustment, characteristics associated with lower coverage included younger maternal age, having a multiple birth, residing in a rural location and higher area material deprivation. In 2019/20, 71.0% of vaccinated individuals received the Tdap vaccination during the recommended gestational window (27-32 wk). Stratified analyses of the pre- and postrecommendation cohorts yielded similar findings to the main analyses with a few gradient differences after adjustment.
Interpretation: During pregnancy, Tdap vaccination coverage increased substantially in Ontario between 2011/12 and 2019/20, most notably after recommendations for universal Tdap vaccination during pregnancy began in Canada. To further improve vaccine coverage in the obstetric setting, public health strategies should consider tailoring their programs to reach subpopulations with lower vaccine coverage.
Competing Interests: Competing interests: Scott Halperin has received research grants or contracts from and has served on ad hoc advisory boards for GlaxoSmithKline, Sanofi Pasteur, Pfizer, Merck, Janssen, Medicago, Entos IMV, CanSino, VBI, Moderna, Precision Nanosystems, AstraZeneca, Seqirus, Novavax and Dynavax (all unrelated to this study). Manish Sadarangani has been an investigator on projects funded by Pfizer, Merck, Moderna, Sanofi Pasteur, Seqirus, Symvivo, VBI Vaccines and GlaxoSmithKline (all unrelated to this study). All funds have been paid to his institute, and he has not received any personal payments. He is chair/deputy chair of 2 data safety monitoring boards for SARS-CoV-2 vaccine trials, involving different vaccines. Kumanan Wilson is the CEO of CANImmunize Inc. and served as a member of the independent data monitoring committee for the Medicago SARS-CoV-2 vaccine trial (all unrelated to this study).
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