A 32-Year Study of the Effect of Pneumococcal Vaccines on Invasive Streptococcus pneumoniae Disease

Abstract

BackgroundWorldwide, Streptococcus pneumoniae commonly causes community-acquired pneumonia, meningitis, septicemia and otitis media. Invasive pneumococcal infection (IPD) represents the most serious presentation, occurs in approximately 1 in 4 cases and engenders case fatality rates (CFR) in pneumonia of 20-25% and meningitis of 35-40%. We investigated IPD for 32 years in an American city to assess the effect of differing pneumococcal vaccines on serotype occurrence and CFR among children and adults. MethodsIn this retrospective study of IPD conducted from 1983-2014, consecutive pneumococcal strains were obtained from inpatients at 3 affiliated hospitals. Each hospital laboratory submitted to our research laboratory S pneumoniae strains recovered from blood and otherwise sterile sites for serotyping by Quellung and penicillin susceptibility tests by ETEST. Clinical data were abstracted from hospital medical records. ResultsIPD occurred among 193 children and 1,003 adults. The overall CFR among adults was 19.2%. Only 2 children died. From 1983-2004, PCV7 serotypes dominated, but after routine PCV7 immunization began in 2000, PCV7 serotypes decreased and nearly disappeared, including penicillin-resistant PCV7 serotypes, few IPD occurred among children and incidence rates declined markedly, which continued after PCV13 replaced PCV7 in 2010. The 11 additional serotypes in PPSV23 became dominant during the past 5 years. Nonvaccine serotypes emerged also. Only serotypes 6B, 15 and 35F showed a significant relative risk of death. ConclusionsCommunity-wide usage of PCV7, then PCV13, changed the predominant serotypes. PCV7 serotypes and IPD among children almost disappeared and PPSV23 and nonvaccine serotypes became more dominant.