Comparative impact of pneumococcal conjugate vaccines on pneumococcal meningitis according to underlying conditions

Abstract

Background: Several underlying conditions increase the risk of pneumococcal meningitis (PM) in childhood. Patients with these diseases are initially considered as an important target of pneumococcal conjugate vaccines (PCVs). Limited data are available for PM in children with underlying conditions. To understand the benefits of PCV7 followed by PCV13 in this vulnerable population, we analyzed the data for a large cohort of pediatric patients with PM in France from 2001 to 2014.

Methods: We conducted hospital-based active surveillance with 227 pediatric wards working with 168 microbiology departments throughout France. Standardized inclusion criteria for PM were used and data were analyzed by a pre-PCV7, post-PCV7 and post-PCV13 period.

Results: From 2001 to 2014, among the 1582 cases of PM, 62.5% were reported in children less than 2years old. Underlying conditions (n=255, 16.1%) accounted for 7.3% of the cases in these young children versus 30.8% for children ⩾2-18years old (p<0.001). After PCV13 implementation, PM cases decreased by 44.0% from 2009 to 2014, mainly in children without underlying conditions. Though the number of children with underlying conditions remained stable, their proportion among overall PM cases increased by 79.1%. Among children with underlying conditions, PCV7 serotypes, 6 additional PCV13 serotypes, additional 11 serotypes in PPV23 and other serotypes accounted for 24.5%, 14.7%, 25.0% and 35.8%, respectively (p<0.001). After PCV13 implementation, 50.0% of PM cases with underlying conditions and 37.9% without underlying conditions were caused by serotypes included in neither PCV13 nor PPV23.

Conclusion: Besides the reduced numbers of PM, its profile has changed, with an increase in cases in proportion of children with underlying conditions accompanied by a striking change in serotype distribution. This underlines the importance of detecting underlying conditions in children with PM in the PCV13 era.

Keywords: Children; Impact; Pneumococcal conjugate vaccine; Pneumococcal meningitis; Underlying conditions.