Effect of a Reduced PCV10 Dose Schedule on Pneumococcal Carriage in Vietnam

This cluster-randomized trial assessed whether a reduced schedule of the 10-valent pneumococcal conjugate vaccine (PCV10) using one primary dose and one booster (1p+1), was noninferior to standard schedules in controlling vaccine-serotype carriage in infants and toddlers in Nha Trang, Vietnam. After a catch-up campaign for children under 3 years old, four dosing regimens (3p+0, 2p+1, 1p+1, 0p+1) were implemented across 24 communes. Annual carriage surveys over 3.5 years showed vaccine-serotype carriage dropped from 11.7% pre-introduction to under 2% across groups in 2020. The 1p+1 and 0p+1 regimens were noninferior to 2p+1 and 3p+0 schedules with no serious vaccine-related adverse events. However, cross-protection against serotype 6A was less robust in reduced-dose groups. The findings suggest single-dose booster regimens may sustain pneumococcal control, offering a cost-effective strategy for middle-income countries transitioning out of Gavi support.

This cluster-randomized trial assessed whether a reduced schedule of the 10-valent pneumococcal conjugate vaccine (PCV10) using one primary dose and one booster (1p+1), was noninferior to standard schedules in controlling vaccine-serotype carriage in infants and toddlers in Nha Trang, Vietnam. After a catch-up campaign for children under 3 years old, four dosing regimens (3p+0, 2p+1, 1p+1, 0p+1) were implemented across 24 communes. Annual carriage surveys over 3.5 years showed vaccine-serotype carriage dropped from 11.7% pre-introduction to under 2% across groups in 2020. The 1p+1 and 0p+1 regimens were noninferior to 2p+1 and 3p+0 schedules with no serious vaccine-related adverse events. However, cross-protection against serotype 6A was less robust in reduced-dose groups. The findings suggest single-dose booster regimens may sustain pneumococcal control, offering a cost-effective strategy for middle-income countries transitioning out of Gavi support.