Abstract
We evaluated the impact of continued 13-valent pneumococcal conjugate vaccine (PCV13) use in the private market (uptake of 61%) in pediatric invasive pneumococcal disease (pIPD) in Portugal (2012–2015). The most frequently detected serotypes were: 3 (n = 32, 13.8%), 14 (n = 23, 9.9%), 1 (n = 23, 9.9%), 7F (n = 15, 6.4%), 19A (n = 13, 5.6%), 6B and 15B/C (both n = 12, 5.2%), and 24F, 10A and 12B (all with n = 10, 4.3%). Taken together, non-PCV13 serotypes were responsible for 42.2% of pIPD with a known serotype. The use of PCR to detect and serotype pneumococci in both pleural and cerebrospinal fluid samples contributed to 18.1% (n = 47) of all pIPD. Serotype 3 was mostly detected by PCR (n = 21/32, 65.6%) and resulted from a relevant number of vaccine failures. The incidence of pIPD varied in the different age groups but without a clear trend. There were no obvious declines of the incidence of pIPD due to serotypes included in any of the PCVs, and PCV13 serotypes still accounted for the majority of pIPD (57.8%). Our study indicates that a higher vaccination uptake may be necessary to realize the full benefits of PCVs, even after 15 years of moderate use, and highlights the importance of using molecular methods in pIPD surveillance, since these can lead to substantially increased case ascertainment and identification of particular serotypes as causes of pIPD.
Highlights
We evaluated the impact of continued 13-valent pneumococcal conjugate vaccine (PCV13) use in the private market in pediatric invasive pneumococcal disease in Portugal (2012–2015)
Discussion pediatric invasive pneumococcal disease (pIPD) incidence varied only modestly and without a clear trend in 2012–2015, in contrast to the significant declines in pIPD incidence seen in 2008–2012, among the younger groups[1]
PCV7 serotypes remain important causes of pIPD, with the slower uptake and lower vaccination coverage reached in Portugal, when compared to countries where PCV7 was introduced in the National Immunization Plan (NIP), and the high resistance of isolates expressing PCV7 serotypes, to penicillin and the macrolides (77% of all PNSP and 41% of all ERP), possibly being important factors for their persistence[1]
Summary
We evaluated the impact of continued 13-valent pneumococcal conjugate vaccine (PCV13) use in the private market (uptake of 61%) in pediatric invasive pneumococcal disease (pIPD) in Portugal (2012–2015). Massive changes in the distribution of Streptococcus pneumoniae serotypes were noted, with major decreases in the incidence of IPD caused by vaccine serotypes (VTs), i.e. those included in PCV formulations[1,2,6,7]. This was accompanied in some cases by an increase in the incidence of IPD due to non-vaccine serotypes (NVTs)[5,8,9]. 0–11 months 12–23 months 2–4 years 5–17 years that some of the serotype changes may not have been triggered by vaccination[1], emphasizing the importance of the natural fluctuations of serotypes and the need to perform continuous epidemiological surveillance
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