Serotype-specific pneumococcal antibodies in breast milk of Gambian women immunized with a pneumococcal polysaccharide vaccine during pregnancy

Background: In breast-feeding populations, immunization during pregnancy with pneumococcal polysaccharide offers a potentially useful approach to preventing pneumococcal disease in young infants. Methods: Breast milk samples were collected at 0, 2, 4 and 6 months after delivery from Gambian women vaccinated during pregnancy (24-32 weeks gestation) with Pneumovax II (n = 56) or Mengivax A&C (n = 57). Specimens were examined for secretory immunoglobulin A (s-IgA) concentration, subclass distribution and avidity specific to pneumococcal serotypes 4, 6B, 14, 19F and 23F and the antigen mixture in Pneumovax 11 by enzyme-linked immunosorbent assay. Colostral s-IgA and IgG concentrations in paired maternal sera were compared. Results: Colostral s-IgA concentrations specific to all pneumococcal polysaccharide antigens investigated were significantly higher (P < 0.05) among Pneumovax II vaccinees. Titers specific to serotypes 4, 6B and 14 and the vaccine formula remained significantly higher during 6 months, and those for 19F were higher during 4 months. Significantly higher concentrations of vaccine antigen-specific s-IgA antibody were sustained for 6 months after delivery (P = 0.011). Comparison of colostral s-IgA and IgG in serum revealed a significant correlation only among Mengivax A&C vaccinees for pneumococcal polysaccharide 23F (r(s) = 0.68; P less than or equal to 0.0001). Vaccination elicited trends toward increased s-IgA2, reaching significance for serotype 14 and the vaccine formula. Immunization elicited significantly higher s-IgA avidities specific to all pneumococcal polysaccharide antigens studied during 6 months. Conclusions: The public health value of immunization during pregnancy with pneumococcal polysaccharide vaccine in breastfeeding populations warrants further evaluation, particularly in populations with a high incidence of pneumococcal disease in early infancy.