BACKGROUND AND OBJECTIVES: Maternal immunization with tetanus, diphtheria, and acellular pertussis vaccine (Tdap) is routinely recommended in many countries as a strategy to protect young infants against severe pertussis infection; few studies have assessed whether prenatal exposure to the vaccine is associated with any longer-term adverse health effects in children. We evaluated the long-term safety of exposure to Tdap vaccination during pregnancy. METHODS: Population-based retrospective cohort study conducted in Ontario, Canada using multiple linked province-wide health administrative databases. All live births between April 2012 and March 2017 were included, and children were followed for up to 6 years to ascertain study outcomes. Children exposed to prenatal Tdap were propensity score matched to unexposed children at a 1:5 ratio. Tdap vaccination during pregnancy was ascertained by using vaccine-specific fee codes. Immune-related (infectious diseases, asthma) and nonimmune-related (neoplasm, sensory disorders) outcomes and a nonspecific morbidity outcome (urgent or inpatient health service use) were evaluated from birth to end of followup. RESULTS: Of 625 643 live births, 12 045 (1.9%) were exposed to Tdap in utero. There were no significant increased risks of adverse childhood outcomes and prenatal Tdap exposure; however, we observed inverse associations (adjusted incidence rate ratio [95% confidence interval]) with upper respiratory infections (0.94 [0.90-0.99]), gastrointestinal infections (0.85 [0.79-0.91]), and urgent and inpatient health service use (0.93 [0.91-0.96]). CONCLUSIONS: Exposure to Tdap vaccination in pregnancy was not associated with any increased risk of adverse health outcomes in early childhood, supporting the long-term safety of Tdap administration in pregnancy.
Bibliographical noteFunding Information:
FUNDING: This study was supported by ICES, which is funded by an annual grant from the Ontario Ministry of Health and Long-Term Care. This research was also supported by operating grants from the Canadian Institutes of Health Research (PJT-159519 and MY7-161351). Dr Kwong was supported by a clinician-scientist award from the Department of Family and Community Medicine, University of Toronto. Dr Sadarangani was supported via salary awards from the BC Children’s Hospital Foundation, the Canadian Child Health Clinician Scientist Program, and the Michael Smith Foundation for Health Research. The funders of this research were not involved in the study design, data analysis, or manuscript preparation or publication decisions. The opinions, results, and conclusions reported in this article are those of the authors and are independent from the funding sources. No endorsement by ICES or the Ontario Ministry of Health and Long-Term Care is intended or should be inferred.
Ethics approval for this project was obtained from the Children’s Hospital of Eastern Ontario Research Ethics Board (Protocol No. 18/10PE), the Ottawa Health Science Network Research Ethics Board (Protocol No. 20180432-01H), and the ICES Privacy Office (Project No. 2019-0901-171- 000).
POTENTIAL CONFLICT OF INTEREST: Dr Halperin’s institution received grants from GlaxoSmithKline and he is a member of ad-hoc advisory committees for GlaxoSmithKline and Sanofi Pasteur (unrelated to this study). Dr Sadarangani has been an investigator on projects (unrelated to this study) funded by Pfizer, Merck, Seqirus, VBI Vaccines, GlaxoSmithKline, Sanofi and Pasteur. All funds have been paid to his institute, and he has not received any personal payments; the other authors have indicated they have no potential conflicts of interest to disclose.
© 2021 by the American Academy of Pediatrics.