Introduction
pneumonia
DISEASE, PNEUMONIA, SECONDARY
The main pneumococcal conjugate vaccine (PCV) formulations currently in use globally are the ten-valent PCV (PCV10; Synflorix, GlaxoSmithKline, Brentford, UK) and 13-valent (PCV13; Prevenar-13, Pfizer, New York, NY, USA). Both vaccine formulations are efficacious and effective against vaccine-serotype invasive pneumococcal disease and all-cause pneumonia hospitalisation in high-income, middle-income, and low-income settings where widespread immunisation has been implemented.In the UK, PCV13 serotype colonisation and disease declined by more than 95% after the introduction of PCV into the public immunisation programme, allowing for the transition from a 2 + 1 to a 1 + 1 dosing schedule in January, 2020.We did an open-label, randomised controlled trial in South Africa, in which children received PCV10 or PCV13 in a 2 + 1 schedule (priming doses at 6 weeks and 14 weeks of age, and a booster at 9 months of age) or a 1 + 1 schedule (with the first dose given either at 6 weeks or 14 weeks of age, with the booster dose given at 9 months of age). The findings showed non-inferiority in immunogenicity, which was the primary objective, of the 1 + 1 compared with 2 + 1 schedules for PCV10 and PCV13.We report on the secondary study objectives of the randomised controlled trial of PCV10 and PCV13 2 + 1 compared with 1 + 1 schedules in South Africa. This included an analysis of colonisation by vaccine serotypes and non-vaccine serotypes following the booster dose of PCV. Furthermore, serotype-specific serum IgG responses were analysed in relation to the putative thresholds proposed by Voysey and colleagues