BACKGROUND Streptococcus pneumoniae carriage is often asymptomatic but can cause invasive pneumococcal disease. Pneumococcal carriage is a prerequisite for disease, with children as main reservoir and transmitters. Childhood carriage can therefore be used to determine which serotypes circulate in the population and which may cause disease in the non-vaccinated population. In 2006, a pneumococcal conjugate vaccine (PCV7) was introduced into the Norwegian Childhood Immunisation Programme, which was replaced by the more valent PCV13 in 2011. We investigated changes in pneumococcal carriage prevalence 4 years after switching to PCV13 compared to three previous surveys, and analysed factors associated with carriage in children. METHODS We conducted a cross-sectional study in Norway, autumn 2015, among children attending day-care centres. We collected questionnaire data and nasopharyngeal swabs to identify pneumococcal serotypes. We compared the carriage prevalence in 2015 with surveys conducted in the same setting performed before widespread vaccination (2006; n = 610), 2 years after PCV7 introduction (2008; n = 600), and 2 years after switching to PCV13 (2013; n = 874). Using multilevel logistic regression we determined the association between pneumococcal carriage and previously associated factors. RESULTS In 2015, 896 children participated, with age ranging from 8 to 80 months. The overall carriage prevalence was 48/100 children [95%CI 44-53] in 2015, 38% [29-46] lower than in 2006 pre-PCV7, and 23% [12-32] lower than in 2013, 2 years after switching to PCV13. The PCV13 carriage prevalence was 2.8/100 children [1.9-4.2] in 2015. Increasing age (p < 0.001), recent antimicrobial use (odds ratio = 0.42 [0.21-0.57]) and being vaccinated (odds ratio = 0.37 [0.29-0.47]) were negatively associated with carriage. CONCLUSIONS Our study showed a continued decrease in overall pneumococcal carriage, mainly fuelled by the decline in vaccine serotypes after vaccine introduction. Childhood vaccination with PCV13 should be continued to keep low PCV13 carriage, transmission and disease. Furthermore, the low prevalence of PCV13-type carriage in children endorse the choice of not recommending PCV13 in addition to the 23-valent pneumococcal polysaccharide vaccine to most medical risk groups in Norway, as little disease caused by these serotypes can be expected.

中文翻译：

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引入PCV13四年后，挪威儿童中肺炎球菌携带率的变化以及与携带相关的因素。

背景技术肺炎链球菌携带通常是无症状的，但是会引起侵袭性肺炎球菌疾病。肺炎球菌感染是疾病的先决条件，儿童是主要的病原体和传播者。因此，可以使用儿童时期的运输来确定哪些血清型在人群中传播，哪些可能在未接种疫苗的人群中引起疾病​​。2006年，将肺炎球菌结合疫苗（PCV7）引入了挪威儿童免疫计划，该疫苗在2011年被更流行的PCV13所取代。我们调查了改用PCV13后4年的肺炎球菌携带率变化，与之前的三项调查相比，分析了与儿童运输有关的因素。方法我们于2015年秋季在挪威对参加日托中心的儿童进行了横断面研究。我们收集了问卷数据和鼻咽拭子，以鉴定肺炎球菌血清型。我们将2015年的马车流行率与在广泛接种疫苗之前（2006; n = 610），引入PCV7两年后（2008; n = 600）和改用PCV13两年后（2013; n = 874）。使用多级逻辑回归分析，我们确定了肺炎球菌感染与先前相关因素之间的关联。结果2015年有896名儿童参加，年龄从8到80个月不等。2015年总体马车普及率是48/100名儿童[95％CI 44-53]，比2006年PCV7之前低38％[29-46]，比2013年（2岁）低23％[12-32]切换到PCV13之后。2015年，PCV13的马车感染率为2.8 / 100名儿童[1.9-4.2]。年龄增长（p <0.001），最近使用的抗菌药物（比值= 0.42 [0.21-0.57]）和接种疫苗（比值= 0.37 [0.29-0.47]）与马车运输负相关。结论我们的研究表明，总体肺炎球菌携带率持续下降，这主要是由于引入疫苗后疫苗血清型的下降所致。儿童应继续接种PCV13疫苗以保持PCV13的低携带，传播和疾病。此外，儿童中PCV13型携带者的患病率低，支持挪威大多数医疗风险人群选择不推荐PCV13和23价肺炎球菌多糖疫苗，因为这些血清型引起的疾病极少。结论我们的研究表明，总体肺炎球菌携带率持续下降，这主要是由于引入疫苗后疫苗血清型的下降所致。儿童应继续接种PCV13疫苗以保持PCV13的低携带，传播和疾病。此外，儿童中PCV13型携带者的患病率低，支持挪威大多数医疗风险人群选择不推荐PCV13和23价肺炎球菌多糖疫苗，因为这些血清型引起的疾病极少。结论我们的研究表明，总体肺炎球菌携带率持续下降，这主要是由于疫苗接种后疫苗血清型的下降所致。儿童应继续接种PCV13疫苗以保持PCV13的低携带，传播和疾病。此外，儿童中PCV13型携带者的患病率低，支持挪威大多数医疗风险人群选择不推荐PCV13和23价肺炎球菌多糖疫苗，因为这些血清型引起的疾病极少。