Changes in pneumococcal carriage prevalence and factors associated with carriage in Norwegian children, four years after introduction of PCV13

Abstract

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 nonvaccinated 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.

Impact of Pneumococcal Vaccination in the Nasopharyngeal Carriage of Streptococcus pneumoniae in Healthy Children of the Murcia Region in Spain

“…In our study, we found, at a statistically significant level, that attending daycare or school was a predisposing factor to NPC and that summer season was a protective factor. Other authors found one or several of those factors [4,32], but situations involving overcrowding, mainly daycare attendance, coincide in all the studies. It seems logical to think that contact with a larger number of possible carriers increases the possibility of NPC.…”

“…NPC and vaccination: It is difficult to assess the impact of vaccination on NPC due to the lack of uniformity in populational studies. Although some studies have communicated a reduction in the percentage of NPC [ 4 , 5 ], most conclude that there are no important variations [ 16 , 17 ], given that after the drop in the VSs an increase in other serotypes has been observed, although not comparable to that observed with the serotype 19A after the introduction of the 7-valent pneumococcal conjugate vaccine (PCV7).…”

“…NPC is high in children (about 30%), especially in those aged less than five years [ 1 , 2 , 3 ], and has a key role in transmission to the rest of the population [ 1 ]. A younger age, attendance to nursery or school, number of siblings, and unfavorable social conditions have all been described as predisposing conditions to NPC [ 1 , 3 , 4 ]. Many factors, such as antibiotic pressure, temporal trends, and the introduction of new conjugate vaccines, may explain the replacement of serotypes and changes in the rate of nasopharyngeal colonization [ 1 , 2 , 3 ].…”

“…These serotypes vary in terms of incidence, disease manifestation, and antibiotic resistance. Since the introduction of pneumococcal conjugate vaccines (PCVs), a global decrease in NPC has been observed for this pathogen, especially of vaccine serotypes (VSs) [ 4 , 5 ]. In Spain, the use of PCVs in children has been heterogeneous among the entire country.…”

The epidemiological characteristics of pediatric Streptococcus pneumoniae isolated from inpatients and outpatients at Beijing Children's Hospital

“…The serotype coverage rates of PCV7, PCV10 and PCV13 were high among the inpatient isolates, meaning that the vaccine serotypes were more common among the inpatient isolates. Many research have proved that PCVs can decrease the pneumococcal carriage rate, disease morbidity and the antibiotic resistance [17][18][19][20]. If the vaccines could be universally immunized, the decreasing effect of vaccine related serotypes could occur earlier or greater in the survey on inpatient isolates.…”