Abstract
Israel implemented use of 7- and 13-valent pneumococcal vaccine in 2009 and 2010, respectively. We describe results of prospective, population-based, nationwide active surveillance of Streptococcus pneumoniae serotype 12F (Sp12F) invasive pneumococcal disease (IPD) dynamics in the 7 years after vaccine introduction. Of 4,573 IPD episodes during July 2009–June 2016, a total of 434 (9.5%) were caused by Sp12F. Sp12F IPD rates (cases/100,000 population) increased in children <5 years of age, from 1.44 in 2009–2010 to >3.9 since 2011–2012, followed by an increase in all ages. During 2011–2016, Sp12F was the most prevalent IPD serotype. Sp12F isolates were mostly penicillin nonsusceptible (MIC >0.06 µg/mL; MIC50 = 0.12) and predominantly of sequence type 3774), a clone exclusively found in Israel (constituting ≈90% of isolates in 2000–2009). The sharp increase, long duration, and predominance of Sp12F IPD after vaccine implementation reflect a single clone expansion and may represent more than a transient outbreak.
Highlights
Israel implemented use of 7- and 13-valent pneumococcal vaccine in 2009 and 2010, respectively
PCV7/PCV13 sequential introduction was followed by a substantial decline in overall invasive pneumococcal disease (IPD) incidence among all age groups, driven mainly by the near-elimination of vaccine serotype disease, but accompanied by a substantial increase in IPD caused by non-PCV13 serotypes [15,16]
Overall IPD We compared the first (2009–2010) and the last (2015– 2016) study years and found that overall IPD rates declined by 34%, from 10.2 to 6.7 (Figure 1)
Summary
Israel implemented use of 7- and 13-valent pneumococcal vaccine in 2009 and 2010, respectively. Since the introduction of pneumococcal conjugated vaccine (PCV), a substantial increase in nasopharyngeal carriage of nonvaccine serotypes (NVT) has been observed in surveillance studies [10,11,12,13,14] and randomized trials assessing the effect of PCV on NVT carriage, comparing vaccinated children and unvaccinated controls [10] This increase in NVT carriage, commonly referred to as the replacement phenomenon, was accompanied by an increase in rates of IPD caused by NVT, diminishing the overall impact of PCVs on IPD rates [10,11]. Sp12F was relatively rare in Israel among IPD cases in the pre-PCV era but has increased noticeably following PCV introduction [15] This serotype has been associated with outbreaks of community-acquired pneumonia and IPD in the United States [17,18,19,20] and Canada [8,21]. An outbreak clone in Canada has been reported to have acquired resistance to macrolides and fluoroquinolones, replacing susceptible clones [21], but in general Sp12F is penicillin susceptible
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