Impact of a multicomponent intervention on maternal Tdap vaccination coverage during a major pertussis resurgence in the province of Quebec, Canada: A quasi-experimental study.

Amid an unprecedented pertussis resurgence in 2024, this study aimed to assess whether a multicomponent intervention implemented in the Chaudière-Appalaches (C-A) region in Quebec, Canada, increased tetanus-diphtheria-acellular pertussis (Tdap) vaccination coverage during pregnancy. We used a quasi-experimental design to compare trends in vaccination coverage from 2022-2024 in the intervention region (C-A) with both the rest of Quebec (RoQ) and seven more comparable regions (SMCR) in Quebec. To assess the intervention's impact while accounting for seasonality, Difference-in-Differences estimates were computed using a quasi-binomial logistic regression model. Throughout the study period, coverage in C-A remained high (70-90%). After the intervention, pertussis vaccination coverage during pregnancy increased more in the C-A region than in the control regions (6.7%, 3.4%, and 2.0% for C-A, RoQ and SMCR, respectively, p < .001). The relative increase in vaccination coverage was also higher in the C-A region than in the control groups. The intervention led to a 4.2 additional percentage points increase in C-A compared to RoQ (95%CI: -0.4-8.8), and a statistically significant 5.8 additional percentage points increase compared to SMCR (95%CI: 1.5-10.1). These results suggest that the multicomponent intervention may have boosted maternal Tdap vaccination coverage during this pertussis outbreak, preventing severe outcomes.