Carriage of Streptoccoccus pneumoniae 7 years after implementation of vaccination program in a population with very high and long-lasting coverage, Italy.
To evaluate how the 7-valent pneumococcal vaccine (PCV7) programme and the very high vaccination coverage reached for over 4 years affected the prevalence of Streptoccoccus pneumoniae serotypes in the paediatric population and to evaluate demographic, behavioural and risk factors for carriage in the post-vaccination era, a cross-sectional study on nasopharyngeal carriage was performed. Six hundred sixty-nine children under the age of 5, representative of the open population, were enrolled by cluster sampling. High sensitive techniques for detection of multi-serotype carriage, i.e. broth enrichment and real-time PCR and sequential PCRs for detection and typing, respectively, were used. Of the 669 enrolled children, 97.8% were compliant with the recommended PCV7 vaccination schedule. Post-stratification adjustment for age was applied considering the Ligurian population as standard population. Age-weighted carriage rate was 50.1% and 78% of carriers were colonized by more than one serotype. The prevalence of carriage increased with age from 22% in the first year of life, to 48.6% in the second year of life and to 60% in the 25-59 month age group. Age-weighted prevalence of any of the PCV7, PCV10 or PCV13 serotypes was 10.3%, 20.3% and 27.5%, respectively. PCV7 serotypes were mainly represented by serotype 4 that was carried since the 3rd year of life and was responsible for invasive pneumococcal disease (IPD) and non-IPD in adults, but not in children confirming the high vaccine effectiveness. Among the serotypes included in recently available vaccines, serotypes 5 and 19A showed a higher prevalence, being carried by 15.2% and 8.8% of the population, respectively. A multivariate analysis showed that age, the presence of child siblings at home and day care attendance covariates were strongly associated with S. pneumoniae carriage. In conclusion, over 7 years of vaccination with PCV7 and very high coverage in the last 4 years has led to low carriage prevalence in the first year of life rapidly increasing in the following years and high prevalence of non-PCV7 serotypes carriage.
Department of Health Sciences, University of Genoa, Via Pastore 1, 16132 Genoa, Italy. filippo.ansaldi@unige.it
Filippo
F
Ansaldi
Daniela
D
de Florentiis
Paola
P
Canepa
Marta
M
Zancolli
Mariano
M
Martini
Andrea
A
Orsi
Paolo
P
Durando
Giancarlo
G
Icardi
D002353:Carrier State / Q000453:epidemiology* / Q000382:microbiology; D002648:Child; D002675:Child, Preschool; D003430:Cross-Sectional Studies; D005260:Female; D006801:Humans; D017589:Immunization Programs; D007223:Infant; D007231:Infant, Newborn; D007558:Italy / Q000453:epidemiology; D008297:Male; D009305:Nasopharynx / Q000382:microbiology; D011008:Pneumococcal Infections / Q000453:epidemiology* / Q000382:microbiology / Q000517:prevention & control; D022242:Pneumococcal Vaccines / Q000008:administration & dosage / Q000276:immunology*; D011159:Population Surveillance / Q000379:methods*; D015995:Prevalence; D012703:Serotyping; D013296:Streptococcus pneumoniae / Q000145:classification / Q000235:genetics / Q000276:immunology / Q000302:isolation & purification*; D013997:Time Factors; D016896:Treatment Outcome; D014611:Vaccination / Q000706:statistics & numerical data*
D022242:Pneumococcal Vaccines