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Serotype diversity and risk factors for pneumococcal carriage among healthy children in Klang Valley, Malaysia: A pre-vaccination cross-sectional study

Year: 2025

Type: article

Abstract: • 39.6% of children had pneumococcal carriage pre-PCV vaccination. • Household size more than five significantly influenced pneumococcal carriage. • 67.5% of children carry multiple serotype pre-PCV vaccination. • Non-vaccine serotypes predominantly colonize unvaccinated children in Klang Valley. Carriage of Streptococcus pneumoniae among children under five facilitates transmission and invasive disease (IPD) progression, contributing to global childhood morbidity and mortality. Pneumococcal conjugate vaccines (PCVs) can reduce disease and carriage prevalence, though their effectiveness varies by regional serotype distribution. Malaysia introduced PCVs into the National Immunization Programme in late 2020, but data on pneumococcal carriage and risk factors in children prior to vaccine implementation remain limited. This study aims to identify pneumococcal carriage, diversity and risk factors among the unvaccinated children in Klang Valley, Malaysia. A cross-sectional study conducted from August 2018 to May 2019 involved 101 healthy children aged 2-5 years from 30 childcare centres in Klang Valley, Malaysia. Oropharyngeal swabs, which are more acceptable for young children though less sensitive than nasopharyngeal swabs for pneumococcal detection, were collected and enriched in Todd Hewitt Broth prior to DNA extraction. Carriage was identified using real-time PCR targeting lytA gene, with positive samples serotyped using conventional multiplex PCR. Demographic and environmental data from structured questionnaires were analyzed for associations with pneumococcal carriage and multiple serotype colonization using logistic regression, Chi-square, and Fisher Exact test. Pneumococcal carriage was detected in 39.6% (n=40) of children, with 33 distinct serotypes identified. Both vaccine serotypes (VTs) and non-vaccine serotypes (NVTs) were detected, with 67.5% of carriers colonized by multiple serotypes. Household size greater than five members was significantly associated with carriage (adjusted OR 4.62, 95% CI 1.07–23.10, p=0.047), while no demographic, behavioral, or environmental factors were significantly associated with multiple serotype colonization. VTs detected (19F, 6A/6B, 3, 1, and 5) were previously associated with IPD in Malaysia. This study provides crucial pre-PCV baseline data on pneumococcal carriage, serotype diversity, and risk factors in children of Klang Valley, Malaysia. The high prevalence of non-vaccine serotypes and frequent co-colonisation highlight the need for ongoing surveillance to detect serotype replacement and guide evaluation of higher-valency PCVs. These findings can inform national immunisation policy and strengthen strategies for monitoring vaccine impact in Malaysia.

Source: IJID Regions

DOI: 10.1016/j.ijregi.2025.100814