Carriage of Streptoccoccus pneumoniae in healthy adults aged 60 years or over in a population with very high and long-lasting pneumococcal conjugate vaccine coverage in children

Abstract

A serial cross-sectional study of nasopharyngeal carriage among adults aged 60 y or over was conducted in winter-spring 2012 with the aim to describe circulating Streptococcus pneumoniae in an area, Liguria Administrative Region, where the vaccine was implemented for a decade and coverage in pediatric age group reached a value close to 100% for more than 5 y, determining a picture of very high vaccine immunological pressure. The serotype-specific carriage picture in adults was compared with that observed in children by means of a cross-sectional study performed one year before using the same sampling and laboratory methods.

Cluster sampling enrolled 283 adults, representative of the open population. Detection of multi-serotype carriage was performed using, real-time PCR and primer specific PCRs.

Carriage prevalence of participants with at least one positive sample adjusted for age, i.e., period prevalence, was 18.7%, considering the Ligurian population as standard population, showing that the pneumococcal carriage in the elderly is not a rare event as emerged in other surveys. The long-term use of PCV7 has resulted in strong decrease of vaccine types carriage among adults and children. A multivariate analysis showed that age class and contact with children attending day care covariates were strongly associated with Streptococcus pneumoniae carriage.

A strong link between the picture observed in < 5-y-old children and ≥ 60-y-old adults emerged: a strong correlation of specific-serotype prevalence between adults and children and risk factor analysis supported the role played by inter-age-group transmission.

Keywords: :

• vaccine prevention
• conjugate vaccine
• S. pneumoniae
• carriage
• replacement

Disclosure of Potential Conflicts of Interest

F.A., G.I. and P.D. have previously participated at speaker’s bureaus and advisory board meetings sponsored by GSK, Novartis, Pfizer and Sanofi Pasteur and have received research funding as principal investigators or co-investigators from Crucell Berna, Novartis, GSK, Pfizer and Sanofi Pasteur. D.dF., P.C., A.C., E.R., R.I., M.M., G.B. and A.O. have no conflict of interest. No other relationships/conditions/circumstances that present a potential conflict of interest exist.

Acknowledgments

Authors would like to thank Pfizer for Financial Support.