Salivary antibody responses to 10-valent pneumococcal conjugate vaccination following two different immunization schedules in a healthy birth cohort

Pneumococcal conjugate vaccines reduce pneumococcal colonization via serotype-specific immunoglobulin G (IgG) at mucosal surfaces. The infant immunization schedule with the ten-valent pneumococcal conjugate vaccine (PCV10) changed from a 3+1 schedule (2-3-4-11 months) to a 2+1 schedule (2-4-11 months) in The Netherlands in 2013. We compared anti-pneumococcal IgG concentrations in saliva between the schedules. IgG was measured using a fluorescent bead-based multiplex immunoassay, at the ages of 6 (post-primary) and 12 (post-booster) months in 51 infants receiving the 3+1 schedule and 68 infants receiving the 2+1 schedule. Post-primary IgG geometric mean concentrations (GMCs) were comparable between schedules for all vaccine serotypes. Post-booster IgG GMCs were significantly lower after the 2+1 schedule for serotypes 4 (p=0.035), 7F (p=0.048) and 23F (p=0.0056). This study shows small differences in mucosal IgG responses between a 3+1 and a 2+1 PCV10 schedule. Future studies should establish correlates of protection against pneumococcal colonization for mucosal antibodies.
Key words: PCV10; mucosal immunity; immunoglobulin G; infant; vaccination schedule.