Impact of 13-Valent Pneumococcal Conjugate Vaccine on Colonisation and Invasive Disease in Cambodian Children.
Turner P., Leab P., Ly S., Sao S., Miliya T., Heffelfinger JD., Batmunkh N., Lessa FC., Walldorf JA., Hyde TB., Ork V., Hossain MS., Gould KA., Hinds J., Cooper BS., Ngoun C., Turner C., Day NPJ.
BACKGROUND: Cambodia introduced the 13-valent pneumococcal conjugate vaccine (PCV13) in January 2015 using a 3+0 dosing schedule and no catch-up campaign. We investigated the effects of this introduction on pneumococcal colonisation and invasive disease in children aged <5 years. METHODS: Six colonisation surveys were done between January 2014 and January 2018 in children attending the outpatient department of a non-governmental paediatric hospital in Siem Reap. Nasopharyngeal swabs were analysed by phenotypic and genotypic methods to detect pneumococcal serotypes and antimicrobial resistance. Invasive pneumococcal disease (IPD) data for January 2012 - December 2018 were retrieved from hospital databases. Pre-PCV IPD data and pre-/post-PCV colonisation data were modelled to estimate vaccine effectiveness (VE). RESULTS: Comparing 2014 with 2016-2018, and using adjusted prevalence ratios, vaccine effectiveness (VE) estimates for colonisation were 16.6% (95% CI 10.6-21.8) for all pneumococci and 39.2% (26.7-46.1) for vaccine serotype (VT) pneumococci. There was a 26.0% (17.7-33.0) decrease in multi-drug resistant pneumococcal colonisation. IPD incidence was estimated to have declined by 26.4% (14.4-35.8) by 2018, with a decrease of 36.3% (23.8-46.9) for VT IPD and an increase of 101.4% (62.0-145.4) for non-vaccine serotype IPD. CONCLUSIONS: Following PCV13 introduction into the Cambodian immunisation schedule there have been declines in VT pneumococcal colonisation and disease in children aged <5 years. Modelling of dominant serotype colonisation data produced plausible vaccine effectiveness estimates.