Fractional Doses of Pneumococcal Conjugate Vaccine — A Noninferiority Trial

This randomized trial conducted in Kenya tested whether fractional doses (20% and 40%) of 10-valent (PCV10) and 13-valent (PCV13) pneumococcal conjugate vaccines are noninferior to full doses in immunogenicity and carriage reduction. Healthy infants were assigned to seven groups, receiving different dose schedules in a two prime–one booster or three prime–no booster format. Immunogenicity was measured by IgG levels and carriage assessed at 9 and 18 months. A 40% dose of PCV13 met noninferiority criteria for 12 of 13 serotypes after primary series and all 13 after the booster. Lower doses and all fractional PCV10 regimens failed to meet noninferiority benchmarks. Carriage prevalence was comparable across PCV13 groups but higher in fractional-dose PCV10 groups. No serious safety signals emerged. The study suggests that 40% doses of PCV13 may offer a cost-effective alternative for sustained pneumococcal control, especially in countries transitioning out of Gavi support.

This randomized trial conducted in Kenya tested whether fractional doses (20% and 40%) of 10-valent (PCV10) and 13-valent (PCV13) pneumococcal conjugate vaccines are noninferior to full doses in immunogenicity and carriage reduction. Healthy infants were assigned to seven groups, receiving different dose schedules in a two prime–one booster or three prime–no booster format. Immunogenicity was measured by IgG levels and carriage assessed at 9 and 18 months. A 40% dose of PCV13 met noninferiority criteria for 12 of 13 serotypes after primary series and all 13 after the booster. Lower doses and all fractional PCV10 regimens failed to meet noninferiority benchmarks. Carriage prevalence was comparable across PCV13 groups but higher in fractional-dose PCV10 groups. No serious safety signals emerged. The study suggests that 40% doses of PCV13 may offer a cost-effective alternative for sustained pneumococcal control, especially in countries transitioning out of Gavi support.