OBJECTIVE: This study estimates the annual population-level impact of 13-valent pneumococcal conjugate vaccine (PCV13) infant national immunization programs (NIPs) on vaccine-type and non-vaccine type invasive pneumococcal disease (IPD) incidence across all ages using national surveillance data.
METHODS: We identified countries (Australia, Canada, England and Wales, Israel, and the United States) with national IPD active surveillance data that introduced the seven-valent PCV (PCV7) followed by PCV13, which also reported annual serotype- and age group-specific incidence. We extracted IPD incidence by serotype groupings [PCV13 minus PCV7 (PCV13-7) serotypes; PCV13-7 serotypes excluding serotype 3; non-PCV13 serotypes; and the 20-valent (PCV20) minus PCV13 (PCV20-13) serotypes] and by age groups (<2 years, 2-4 years, 5-17 years, 18-34 years, 35-49 years, 50-64 years, and ≥65 years). For each country, we calculated the annual relative change in IPD incidence (percent change), and the corresponding incidence rate ratio (IRR), for seven years post introduction compared to the year prior to PCV13 program initiation.
RESULTS: PCV13-7 vaccine-type IPD incidence consistently decreased over time following introduction of PCV13 across countries, reaching an approximate steady state after 3-4 years in ages <5 years, with roughly 60% to 90% decrease (IRRs = 0.1 to 0.4) and after 4-5 years in ages >65 years with approximately 60% to 80% decrease (IRRs = 0.2 to 0.4). Incidence declines were more substantial for the PCV13-7 grouping when excluding serotype 3. Non-PCV13 serotype incidence was variable by country and age group, ranging from virtually no serotype replacement compared to the PCV7 period across ages in the United States to increases for other countries ranging from 10% to 204% (IRRs = 1.10 to 3.04) in children <5 years and 41% to 123% (IRRs = 1.41 to 2.23) in ages >65 years.
CONCLUSIONS: Countries with longstanding PCV13 infant NIPs have observed substantial direct and indirect benefits which are demonstrated in this study by the reduction in PCV13-7 IPD incidence compared to PCV7 period. Over time, non-PCV13 serotypes have emerged in response to the reduction of incidence of PCV13-unique serotypes. Higher-valent PCVs are needed to address this emerging pneumococcal disease burden, as well as the direct vaccination of both pediatric and adult populations against the most prevalent circulating serotypes.
