Effectiveness of the 13-valent pneumococcal conjugate vaccine against invasive pneumococcal disease in South African children : a case-control study
CITATION: Cohen, C., et al. 2017. Effectiveness of the 13-valent pneumococcal conjugate vaccine against invasive pneumococcal disease in South African children : a case-control study. Lancet Global Health, 5(3):e359-e369, doi:10.1016/S2214-109X(17)30043-8.
The original publication is available at http://www.thelancet.com/journals/langlo
Background: The 13-valent pneumococcal conjugate vaccine (PCV13) was designed to include disease-causing serotypes that are important in low-income and middle-income countries. Vaccine eff ectiveness estimates are scarce in these settings. South Africa replaced PCV7 with PCV13 in 2011 using a 2 + 1 schedule. We aimed to assess the eff ectiveness of two or more doses of PCV13 against invasive pneumococcal disease in children with HIV infection and in those not infected with HIV. Methods: Cases of invasive pneumococcal disease in children aged 5 years or younger were identifi ed through national laboratory-based surveillance. Isolates were serotyped with the Quellung reaction or PCR. We sought in-hospital controls for every case, matched for age, HIV status, and study site. We aimed to enrol four controls for every case not infected with HIV and six controls for every case with HIV infection (case-control sets). With conditional logistic regression, we calculated vaccine eff ectiveness as a percentage, with the equation 1 – [adjusted odds ratio for vaccination] × 100. We included data from an earlier investigation of PCV7 to assess vaccine eff ectiveness in children exposed to but not infected with HIV and in malnourished children not infected with HIV. Findings: Between January, 2012, and December, 2014, we enrolled children aged 16 weeks or older to our study: 240 were cases not infected with HIV, 75 were cases with HIV infection, 1118 were controls not infected with HIV, and 283 were controls with HIV infection. The eff ectiveness of two or more doses of PCV13 against PCV13-serotype invasive pneumococcal disease was 85% (95% CI 37 to 96) among 11 case-control sets of children not infected with HIV and 91% (–35 to 100) among three case-control sets of children with HIV infection. PCV13 eff ectiveness among 26 case-control sets of children not infected with HIV was 52% (95% CI –12 to 79) against all-serotype invasive pneumococcal disease and 94% (44 to 100) for serotype 19A. Vaccine eff ectiveness against PCV7-serotype invasive pneumococcal disease was 87% (95% CI 38 to 97) in children exposed to HIV but uninfected and 90% (53 to 98) in malnourished children not infected with HIV. Interpretation: Our results indicate that PCV13 in a 2 + 1 schedule is eff ective for preventing vaccine-type pneumococcal infections in young children not infected with HIV, including those who are malnourished or who have been exposed to HIV. Although the point estimate for PCV13 vaccine eff ectiveness in children infected with HIV was high, it did not reach signifi cance, possibly because of the small sample size. These fi ndings support recommendations for widespread use of pneumococcal conjugate vaccine in low-income and middle-income countries.