Pneumococcal carriage in young children after introduction of PCV13 in Hong Kong

Abstract

ObjectivesPneumococcal conjugate vaccine (PCV) has been included in Hong Kong’s Childhood Immunization Programme since 2009. This study aimed to assess nasopharyngeal pneumococcal carriage rate, serotypes and antimicrobial resistance pattern in young children after the introduction of 13-valent PCV (PCV13). Study designA community-based, cross-sectional surveillance study was performed on healthy infants attending eleven Maternal and Child Health Centres across different parts of Hong Kong. Nasopharyngeal swabs were obtained from healthy children aged 2, 12 and 18months during their visit to the centers for immunization from June 2013 to June 2014. Pneumococcal isolates were serotyped and tested for antimicrobial resistance. Details of the demographics, family composition, vaccination history and medical history was obtained through interview of the guardians. Results1541 children were recruited. The overall carriage rate was 5.5%. Children aged 12 and 18months were more likely to have pneumococcal colonization (12months OR: 2.88; 95% CI: 1.41–5.87 and 18months OR: 2.19, 95% CI: 1.05–4.57). Recent respiratory symptoms and presence of siblings younger than 6years were independently associated with pneumococcal carriage. Eighty-four pneumococcal isolates were serotyped. The most prevalent serogroup/types were 15 (15B/C, 16.7%; 15A/F, 9.5%), 6C (15.5%) and 23A (13.1%). Overall, 2.4% of the isolates were heptavalent PCV serotypes, 10.7% were PCV13 serotypes and 89.3% were non-PCV13 serotypes. The proportions of penicillin, cefotaxime and erythromycin non-susceptible isolates were 7.3%, 13.4% and 79.3% respectively. ConclusionThe rate of pneumococcal carriage was low in young children in Hong Kong and compared to previous local studies there appears to have been an overall reduction in the carriage rate after the introduction of PCV. Likely serotype replacement was noted with a predominance of non-vaccine serotypes in pneumococcal carriage with the emergence of serogroup/type 15 and 6C.