Invasive pneumococcal disease incidence in children and adults in France during the pneumococcal conjugate vaccine era: an interrupted time-series analysis of data from a 17-year national prospective surveillance study

Background: the long-term benefits of pneumococcal conjugate vaccines (PCVs) remain unknown because of serotype replacement. We aimed to estimate the effect of PCV implementation on invasive pneumococcal disease incidence in France. Methods: we did a quasi-experimental interrupted time-series analysis using data from a French national prospective surveillance system. We included all invasive pneumococcal disease cases in children and adults from more than 250 participating hospitals between Jan 1, 2001, and Dec 31, 2017. The primary outcome was incidence of invasive pneumococcal disease (meningitis and non-meningitis) over time, analysed by segmented regression with autoregressive error. Isolates were serotyped by latex agglutination with antiserum samples. Findings: we included 75 903 patients with invasive pneumococcal disease, including 4302 (5·7%) children younger than 2 years and 37 534 (49·4%) adults aged 65 years or older. Before PCV7 implementation, the estimated monthly incidence of invasive pneumococcal disease was 0·78 cases per 100 000 inhabitants, which did not change significantly up to May, 2010. PCV13 implementation in 2010 was followed by a significant decrease in the incidence of invasive pneumococcal disease (-1·5% per month, 95% CI -2·2 to -0·8), reaching an estimated monthly incidence of 0·52 cases per 100 000 inhabitants in December, 2014. From January, 2015, the incidence rebounded (1·8% per month, 95% CI 1·0 to 2·6), reaching an estimated monthly incidence of 0·73 cases per 100 000 inhabitants in December, 2017. The estimated monthly incidence increased from 0·93 cases per 100 000 in December, 2014, to 1·73 cases per 100 000 in December, 2017, for children younger than 2 years, and from 1·54 cases per 100 000 in December, 2014, to 2·08 cases per 100 000 in December, 2017, for adults aged 65 years or older. The main non-PCV13 serotypes involved in the increase were 24F in young children and 12F, 22F, 9N, and 8 in adults aged 65 years or older. Interpretation: PCV13 implementation led to a major reduction in the incidence of invasive pneumococcal disease. However, a rebound in cases among children and adults since 2015, driven by several emerging non-PCV13 serotypes, jeopardises the long-term PCV benefits. These findings, if confirmed in the coming years, should be considered in the development of next-generation PCVs and might guide policy makers in the selection of future pneumococcal vaccines.