Pneumococcal Colonization in Healthy Adult Research Participants in the Conjugate Vaccine Era, United Kingdom, 2010–2017

Pneumococcal colonization is rarely studied in adults, except as part of family surveys. We report the outcomes of colonization screening in healthy adults (non-smokers without major comorbidities or contact with children under five years) who had volunteered to take part in clinical research. Using nasal wash culture, we detected colonization in 6.5% (52/795) of volunteers. Serotype 3 was the commonest serotype (10/52). The majority of the remainder (35/52) were non-vaccine serotypes, but we also identified persistent circulation of serotypes 19A and 19F. Resistance to at least one of six antibiotics tested was found in 8/52 isolates.