No long-term evidence of hyporesponsiveness after use of pneumococcal conjugate vaccine in children previously immunized with pneumococcal polysaccharide vaccine

Background: A randomized controlled trial in Fiji examined theimmunogenicity and effect on nasopharyngeal carriage after 0, 1,2, or 3 doses of 7-valent pneumococcal conjugate vaccine (PCV7;Prevnar) in infancy followed by 23-valent pneumococcalpolysaccharide vaccine (23vPPV; Pneumovax) at 12 months ofage. At 18months of age, children given 23vPPVexhibitedimmunehyporesponsiveness to a micro-23vPPV (20%) challenge dose interms of serotype-specific IgG and opsonophagocytosis, while23vPPV had no effect on vaccine-type carriage.Objective: This follow-up study examined the long-term effectof the 12-month 23vPPV dose by evaluating the immuneresponse to 13-valent pneumococcal conjugate vaccine (PCV13)administration 4 to 5 years later.Methods: Blood samples from 194 children (now 5-7 years old)were taken before and 28 days after PCV13 boosterimmunization. Nasopharyngeal swabs were taken before PCV13immunization. We measured levels of serotype-specific IgG toall 13 vaccine serotypes, opsonophagocytosis for 8 vaccineserotypes, and memory B-cell responses for 18 serotypes beforeand after PCV13 immunization.Results: Paired samples were obtained from 185 children. Therewere no significant differences in the serotype-specific IgG,opsonophagocytosis, or memory B-cell response at either timepoint between children who did or did not receive 23vPPV at12 months of age. Nasopharyngeal carriage of PCV7 and23vPPV serotypes was similar among the groups. Priming with1, 2, or 3 PCV7 doses during infancy did not affect serotypespecificimmunity or carriage.Conclusion: Immune hyporesponsiveness induced by 23vPPV intoddlers does not appear to be sustained among preschoolchildren in this context and does not affect the pneumococcalcarriage rate in this age group.