Impact of vaccinating pregnant women against pertussis on hospitalizations of children under one year of age in a tertiary hospital in Catalonia.

Introduction: The recommendation for pertussis vaccination in pregnancy was established in Catalonia in February 2014. The objective of this study was to compare the hospitalization rate for pertussis in children under one year of age before and after the implementation of the vaccination program.

Methods: Observational and retrospective study of patients under one year of age admitted to hospital with a diagnosis of pertussis. The hospitalization rate of patients under one year of age of the period prior to the vaccination program (2008-2013) was compared with the period with vaccination program (2014-2019) in the total of children under one year of age and in 2subgroups: children under 3 months and between 3-11 months.

Results: Hospitalization rate was significantly lower in the period with vaccination program in children under one year of age and specifically in children under 3 months (2.43 vs. 4.72 per 1,000 person-years and 6.47 vs. 13.11 per 1,000 person-years, respectively). The rate ratios were: 0.51 (95% CI 0.36-0.73) for children under one year of age; 0.49 (95% CI 0.32-0.75) for those younger than 3 months and 0.56 (95% CI 0.30-1.03) for those with 3-11 months. No statistically significant differences were observed in the clinical severity between both periods.

Conclusion: The introduction of the pertussis vaccination program in pregnancy was associated with a global lower hospitalization rate for pertussis in children under one year of age and specifically in those under 3 months of age.