Pneumococcal carriage following PCV13 delivered as one primary and one booster dose (1+1) compared to two primary doses and a booster (2+1) in UK infants.

Abstract

In January 2020 the UK changed from a 2+1 schedule for 13-valent pneumococcal conjugate vaccine (PCV13) to a 1+1 schedule (doses at 3 and 12months) based on a randomized immunogenicity trial comparing the two schedules. Carriage prevalence measured at the time of booster and 6months later in 191 of the 213 study infants was 57% (109/191) and 60% (114/190) respectively. There were eight episodes of vaccine-type (VT) or vaccine-related 6C carriage in the 2+1 and six in the 1+1 group; ≥4-fold rises in serotype-specific IgG in 71 children with paired post-booster and follow up blood samples at 21-33months of age were found in 20% (7/35) of the 2+1 and 15% (6/41) of the 1+1 group. VTs identified in carriage and inferred from serology were similar comprising 3, 19A and 19F. Dropping a priming dose from the 2+1 PCV 13 schedule did not increase VT carriage in the study cohort. Ongoing population level carriage studies will be important to confirm this.