Prevalence, Serotype Distribution, and Risk Factors Associated With Streptococcus pneumoniae Carriage in Older Adults...

The burden of pneumococcal disease in older adults remains high in the postpneumococcal conjugate vaccine (PCV) era. We hypothesized that older adults may represent a carriage reservoir of Streptococcus pneumoniae.

Paired naso- and oropharyngeal (NP and OP) swabs and questionnaires were collected during 2019-2022 from adults ≥65 years of age. Pneumococcal carriage and serotype distribution were determined by phenotypical and molecular methods.

A total of 172/1764 participants (9.8% [95% confidence interval {CI} 8.4-11.2]) were positive for carriage of S. pneumoniae by either culture (0.3%) or lytA/piaB DNA in NP (2.0%) or OP (8.4%) samples. Overall, 118 serogroup- or serotype-specific carriage events were identified by multiplex polymerase chain reaction across 16 distinct serospecificities in 93 samples, while 79 samples were nontypeable. PCV13 types accounted for 8.0%, nonvaccine types for 11.0% and polysaccharide pneumococcal vaccine 23 (PPV23)/non-PCV13 types for 81.0%. All carriage serotypes, except serotype 2, had been identified in invasive pneumococcal disease (IPD) isolates among adults ≥65 years during 2019-2022. Having young grandchildren was associated with increased odds of carriage (adjusted odds ratio [OR] 1.8, 95% CI 1.2-2.5, P = .0031). No association between PPV23 immunization and carriage was observed (OR 0.8, 95% CI .5-1.3).

Older adults were carriers of a wide range of IPD-causing serotypes. Both carriage and IPD serotypes were mainly comprised of non-PCV13 serotypes. Immunization with higher valency conjugated vaccines is likely required to reduce residual pneumococcal disease among older adults.