OBJECTIVES: This study aims to assess the future impact of persistent low VCRs (vaccination coverage rates) on pertussis epidemiology over 8 years and the resulting direct medical and societal costs.

METHODS: A dynamic transmission model previously developed by Coudeville et al. (2008) was adapted to capture the main characteristics of pertussis vaccination in Brazil, as well as the main clinical features of pertussis infections. The population was stratified in five age categories: <1, 1-4, 5-9, 10-19 and ≥20 years old. Costs parameters were extracted from published data. The model was calibrated on reported pertussis incidence for the period 2010-2015, adjusted for under-reporting and a 100-sample probabilistic sensitivity analysis for the 2022-2029 period was conducted.

RESULTS: When compared with a scenario of VCRs restored to 2010 level (VCRs for doses 1, 2 and 3 = 99%), if the VCRs remain at the 2019 level (VCRs for doses 1, 2 and 3 = 79%, 74.5% and 70%, respectively), our model predicts an increased pertussis incidence driven by unvaccinated cohorts, with twice more cases in infants under 1 year of age (356,000 vs 175,000 cases) and 3-fold more cases in children aged 1-4 years (158,000 vs. 56,000 cases). Annual direct public healthcare costs for a possible pertussis outbreak could rise from US$3.9M in the 2010 VCRs scenario and to US$8.4M with the 2019 VCRs. Annual societal costs due to years of life lost could be US$34M and US$71M for the VCRs of 2010 and 2019, respectively.

CONCLUSIONS: Low VCRs could result in an annual incremental cost of US$23.3M, rising to US$41.5M in a potential outbreak. Mitigating the risks of low VCRs requires maintaining vaccine acceptability in the population. The use of less reactogenic acellular vaccines compared to whole cell vaccines could contribute in this manner to avoiding the scenario estimated through the model.