Abstract
Increasing the uptake of the 13-valent pneumococcal conjugate vaccine (PCV13) in children is expected to alter the serotypes causing invasive pneumococcal disease (IPD) in adults due to herd protection. We characterized 2172 cases of adult IPD in 2015–2018 in Portugal after the introduction of PCV13 in the national immunization plan of 2015. Among the 58 detected serotypes, serotypes 8 (n = 413; 19%), 3 (n = 334; 15%), 22F (n = 148; 7%), 14 (n = 138; 6%), and 19A (n = 116; 5%) were the most frequent. Among PCV13 serotypes, 7F and 19A IPD decreased, but serotype 3 IPD remained stable. The non-PCV13 serotypes were a heterogeneous group, with serotypes 23A and 23B enriched among CSF cases; serotype 8 associated with younger patients; and serotypes 22F, 6C, and 31 associated with older patients. The continued increase of serotype 8 IPD was one of the drivers for the increased coverage of the 23-valent pneumococcal polysaccharide vaccine (PPV23; 80% in 2015–2018). Antimicrobial resistance was associated with older age and serotypes 6C, 11A, 14, 15A, 19A, and 19F. Three years after the introduction of PCV13 in the NIP with an uptake of >95%, the proportion of PCV13 serotypes causing IPD in adults stabilized in Portugal. The direct vaccination of adults may be important in preventing IPD in this age group.
Highlights
Published: 8 May 2021The introduction of pneumococcal conjugate vaccines (PCVs) in children led to changes in the incidence and serotypes causing invasive pneumococcal disease (IPD), in vaccinated children and in adults
Serotypes were classified into vaccine serotypes, i.e., those included in PCV7, PCV13, PCV15, PCV20, and PPV23, or as non-vaccine serotypes (NVTs)
In adults through herd immunity [19,20]. This is thought to be related to the proportion of vaccinated children [19], so the increase in uptake anticipated from the introduction of PCV13 in the NIP in Portugal was expected to result in further effects in adult IPD
Summary
The introduction of pneumococcal conjugate vaccines (PCVs) in children led to changes in the incidence and serotypes causing invasive pneumococcal disease (IPD), in vaccinated children and in adults. In Portugal, as elsewhere, the use of increasing valency PCVs in children led to changes in the serotypes causing. The use of the 7-valent PCV (PCV7) in children led to a decrease in the proportion of PCV7 serotypes in adult IPD in Portugal in 2006–2008, with the most frequent serotypes being 3, 1, 7F, 19A, and 14 [3]. After the introduction of PCV13 for children vaccinations in 2010, a decline in the proportion of the additional serotypes included in PCV13 was observed in adult IPD, mostly driven by decreases in the proportion
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