Differences in the Impact of Pneumococcal Serotype Replacement in Individuals With and Without Underlying Medical Conditions

Abstract

Background. Pneumococcal conjugate vaccines (PCVs) have had a well-documented impact on the incidence of invasive pneumococcal disease (IPD). However, declines in IPD due to vaccine-targeted serotypes have been partially offset by increases in IPD due to nonvaccine serotypes (NVTs). The goal of this study was to quantify serotype-specific changes in the incidence of IPD that occurred in different age groups, with or without certain comorbidities, following the introduction of 7-valent pneumococcal conjugate vaccine (PCV7) and 13-valent pneumococcal conjugate vaccine (PCV13) in the childhood vaccination program in Denmark. Methods. We used nationwide surveillance data for IPD and a hierarchical Bayesian regression framework to estimate changes in the incidence of IPD associated with the introduction of PCV7 (2007) and PCV13 (2010) while controlling for serotype-specific epidemic cycles and unrelated secular trends. Results. Following the introduction of PCV7 and PCV13 in children, the net impact of serotype replacement varied considerably by age group and comorbidities. Differences in the magnitude of serotype replacement were due to variations in the incidence of NVTs in the different risk groups before the introduction of PCVs. The relative increases in the incidence of IPD caused by specific NVTs did not differ appreciably between risk groups in the postvaccination period. Serotype replacement offset a greater proportion of the benefit of PCVs in strata in which the NVTs comprised a larger proportion of cases prior to the introduction of the vaccines. Conclusions. These findings could help to predict the impact of next-generation PCVs in specific risk groups. Keywords. pneumococcus; serotype replacement; conjugate vaccines; Bayesian hierarchical model. Pneumococcal conjugate vaccines (PCVs) have had a well-documented impact on the incidence of invasive pneumococcal disease (IPD) worldwide [1-5]. Because PCVs interrupt transmission of pneumococcus among healthy children, the introduction of PCVs has led to reductions in the incidence of IPD among both vaccinated children and (indirectly) among unvaccinated adults [1, 6]. A meta-analysis of data from the United States, Europe, and Australia found that, on average, IPD due to serotypes in the 7-valent PCV (PCV7) declined by approximately 90% among adults [1]. However, these declines in IPD due to vaccine-targeted serotypes (VTs) were at least partially offset by increases in IPD caused by nonvaccine serotypes (NVTs), a phenomenon known as serotype replacement [1, 7]. The net benefit of PCVs is therefore determined by both

Invasive Pneumococcal Disease in Persons With Predisposing Factors is Dominated by Non-vaccine Serotypes in Southwest Sweden

“…Among persons with predisposing factors, the non-PCV13 serotypes clearly dominated. This was similar to the US and UK in the post-vaccine era [21,22,32]. This raises the for immunocompetent adults ≥ 65 years of age due to the diminishing incidence of PCV13 serotypes [2,37].…”

“…The changes in serotype distribution found here are in concordance with studies from US and Western Europe. These also show a non-PCV serotype dominance among IPD cases, with serotype 3 being the most prevalent in many countries [4,8,21,22,32].…”

Estimating the Vaccine Effectiveness Against Serotype 3 for the 13-Valent Pneumococcal Conjugate Vaccine: A Dynamic Modeling Approach

“…In summary, these results highlight that a nontrivial, possibly low level of indirect protection against serotype 3 is conferred by PCV13 and could reflect impact against carriage acquisition, density, or duration. However, it should also be noted that several serotypes that are known to cause IPD, including serotype 3, undergo multiyear epidemic patterns that are independent of PCVs [30] and that may be due to a variety of factors. The observed differences in the PCV13 and PCV10 countries could also have been due to factors other than vaccine, including differences in the serotype distribution of nasopharyngeal carriage among children in the pre-PCV10 or PCV13 vaccine periods [31].…”

Aktuelles zur Meningokokken- und Pneumokokken-Impfung

“…Relativ rasch nach Einführung des PCV7 war allerdings ein Replacement durch nicht im Impfstoff enthaltene Serotypen zu beobachten [24,25]. Durch diese Serotypen werden aktuell vermehrt IPDs verursacht, wie bereits erwähnt [18,23,26,27].…”