Impact of vaccine schedule change on pertussis epidemiology in France: a modelling and serological study

• Published in: The Lancet infectious diseases 2022-02, Vol.22 (2), p.265-273
• Main Authors: Paireau, Juliette, Guillot, Sophie, Aït El Belghiti, Fatima, Matczak, Soraya, Trombert-Paolantoni, Sabine, Jacomo, Véronique, Taha, Muhamed-Kheir, Salje, Henrik, Brisse, Sylvain, Lévy-Bruhl, Daniel, Cauchemez, Simon, Toubiana, Julie
• Format: Article
• Language: English
• Subjects: Life Sciences; Santé publique et épidémiologie; Statistics
• ISSN: 1473-3099; 1474-4457
• DOI: 10.1016/S1473-3099(21)00267-X

Background: In 2013, France modified its pertussis vaccination schedule to remove one dose at 3 months of age and change the age of the booster dose from 16 to 11 months. We aimed to assess the subsequent impact on pertussis epidemiology in France. Methods: We analysed the PCR test results of nasopharyngeal swabs (N=7493) collected from symptomatic outpatients aged 2-20 years old between 2012 and 2019 in France. We developed a negative binomial regression model for the number of pertussis cases by year and age. The linear predictor included the year, the age group, the population size and a proxy of waning immunity that could vary with vaccine schedule. We also compared the anti-pertussis toxin (PT) antibody levels of 315 children born before and after the vaccine schedule change. Findings: The model that best fitted the 2012-2018 epidemiological data supported a faster waning of immunity following vaccination with the new vaccine schedule. Three years after vaccination, the risk of developing pertussis was 1.7 (95% CI, 1.4-2.0) times higher for children vaccinated according to the new schedule than those vaccinated according to the previous schedule. The model correctly predicted the age distribution of cases in 2019. Anti-PT IgG levels were significantly lower in children born after implementation of the new schedule, compared to children born before. Interpretation: A shorter-lived protection induced by the 2/4+11 vaccine schedule recommended in France since 2013 is associated with an increase of pertussis cases in 2-5-year olds.