Age-dependent prevalence of nasopharyngeal carriage of streptococcus pneumoniae before conjugate vaccine introduction: a prediction model based on a meta-analysis.
BACKGROUND
Data on the prevalence of nasopharyngeal carriage of S.pneumoniae in all age groups are important to help predict the impact of introducing pneumococcal conjugate vaccines (PCV) into routine infant immunization, given the important indirect effect of the vaccine. Yet most carriage studies are limited to children under five years of age. We here explore the association between carriage prevalence and serotype distribution in children aged ≥5 years and in adults compared to children.


METHODS
We conducted a systematic review of studies providing carriage estimates across age groups in healthy populations not previously exposed to PCV, using MEDLINE and Embase. We used Bayesian linear meta-regression models to predict the overall carriage prevalence as well as the prevalence and distribution of vaccine and nonvaccine type (VT and NVT) serotypes in older age groups as a function of that in <5 y olds.


RESULTS
Twenty-nine studies compromising of 20,391 individuals were included in the analysis. In all studies nasopharyngeal carriage decreased with increasing age. We found a strong positive linear association between the carriage prevalence in pre-school childen (<5 y) and both that in school aged children (5-17 y olds) and in adults. The proportion of VT serotypes isolated from carriers was consistently lower in older age groups and on average about 73% that of children <5 y among 5-17 y olds and adults respectively. We provide a prediction model to infer the carriage prevalence and serotype distribution in 5-17 y olds and adults as a function of that in children <5 years of age.


CONCLUSIONS
Such predictions are helpful for assessing the potential population-wide effects of vaccination programmes, e.g. via transmission models, and thus assist in the design of future pneumococcal conjugate vaccination strategies.
Department of Infectious Disease Epidemiology, London School of Hygiene and Tropical Medicine, London, United Kingdom.
Olivier
O
Le Polain de Waroux
Department of Infectious Disease Epidemiology, London School of Hygiene and Tropical Medicine, London, United Kingdom.
Stefan
S
Flasche
Department of Medical Statistics, London School of Hygiene and Tropical Medicine, London, United Kingdom.
David
D
Prieto-Merino
Department of Infectious Disease Epidemiology, London School of Hygiene and Tropical Medicine, London, United Kingdom.
W John
WJ
Edmunds
D017677:Age Distribution; D001499:Bayes Theorem; D002353:Carrier State / Q000453:epidemiology* / Q000382:microbiology; D004197:Disease Reservoirs / Q000382:microbiology; D006801:Humans; D016014:Linear Models; D009305:Nasopharynx / Q000382:microbiology*; D011008:Pneumococcal Infections / Q000453:epidemiology / Q000517:prevention & control*; D022242:Pneumococcal Vaccines / Q000008:administration & dosage*; D015995:Prevalence; D013296:Streptococcus pneumoniae / Q000302:isolation & purification*; D014611:Vaccination; D018074:Vaccines, Conjugate / Q000008:administration & dosage
D022242:Pneumococcal Vaccines; D018074:Vaccines, Conjugate