Pneumococcal Colonization in the FamilialContext and Implications for Anti-PneumococcalImmunization in Adults: Results fromthe BINOCOLO Project in Sicily

The spread of Streptococcus pneumoniae within families has been scarcely investigated sofar. This feasibility study aimed to estimate the prevalence of pneumococcal carriage in school-agedchildren and co-habiting relatives and to explore the potential link between the family environmentand the sharing of pneumococcal serotypes covered by the vaccine. Oropharyngeal samples of146 subjects belonging to 36 different family groups were molecularly tested for pneumococcaldetection and serotyping. The overall prevalence of pneumococcal carriage was 65.8% (n = 96/146),whereas it was higher among schoolchildren (77.8%, n = 28/36); subjects of seven years of age hadthe highest odds of being colonized (odds ratio, OR = 5.176; p = 0.145). Pneumococcal serotypesincluded in the 13-valent conjugate vaccine formulation were largely detected in the study populationand multiple serotypes colonization was considerable. Factors relating to a close proximity amongpeople at the family level were statistically associated with pneumococcal carriage (OR = 2.121;p = 0.049), as well as active smoking habit with a clear dose-response effect (ORs = 1.017–3.326).About half of family clusters evidenced similar patterns of carried pneumococcal serotypesand the odds of sustaining a high level of intrafamilial sharing increased with household size(ORs = 1.083–5.000). This study highlighted the potential role played by the family environment insustaining both the circulation and horizontal transmission of pneumococcus.