Effectiveness of the 13-valent pneumococcal conjugate vaccine in preventing invasive pneumococcal disease in children aged 7-59 months. A matched case-control study.

Background: The 13-valent pneumococcal conjugate vaccine (PCV13) was licensed based on the results of immunogenicity studies and correlates of protection derived from randomized clinical trials of the 7-valent conjugate pneumococcal vaccine. We assessed the vaccination effectiveness (VE) of the PCV13 in preventing invasive pneumococcal disease (IPD) in children aged 7-59 months in a population with suboptimal vaccination coverage of 55%.

Methods: The study was carried out in children with IPD admitted to three hospitals in Barcelona (Spain) and controls matched by hospital, age, sex, date of hospitalization and underlying disease. Information on the vaccination status was obtained from written medical records. Conditional logistic regression was made to estimate the adjusted VE and 95% confidence intervals (CI).

Results: 169 cases and 645 controls were included. The overall VE of ≥1 doses of PCV13 in preventing IPD due to vaccine serotypes was 75.8% (95% CI, 54.1-87.2) and 90% (95% CI, 63.9-97.2) when ≥2 doses before 12 months, two doses on or after 12 months or one dose on or after 24 months, were administered. The VE of ≥1 doses was 89% (95% CI, 42.7-97.9) against serotype 1 and 86.0% (95% CI, 51.2-99.7) against serotype 19A. Serotype 3 showed a non-statistically significant effectiveness (25.9%; 95% CI, -65.3 to 66.8).

Conclusions: The effectiveness of ≥1 doses of PCV13 in preventing IPD caused by all PCV13 serotypes in children aged 7-59 months was good and, except for serotype 3, the effectiveness of ≥1 doses against the most frequent PCV13 serotypes causing IPD was high when considered individually.