SERUM, BREAST-MILK, AND INFANT ANTIBODY AFTER MATERNAL IMMUNIZATION WITH PNEUMOCOCCAL VACCINE

Pneumococci are a leading cause of severe bacterial disease in infants and children world wide, A possible means of protecting infants in th e first few months of life is immunisation of the mother during prospe ctively assessed pneumococcal pregnant women to determine the amount p neumococcal antibody transmitted to the infants in serum and milk and the half-life of the passively acquired antibody. Healthy pregnant wom en in Dhaka, Bangladesh, were randomised to receive pneumococcal or me ningococcal vaccine with routine prenatal tetanus immunisation at 30-3 4 weeks of gestation. Serum and breast milk specimens from the mothers and sera from infants were collected up to 22 weeks of age and assaye d for specific serum IgG, IgG1, and IgG2 and for milk IgA antibodies t o pneumococcal serotypes 6B and 19F. 55 mothers and 56 infants were fo llowed from birth to five months, Women who received pneumococcal vacc ine had geometric mean antibody increases of 2.6 and 3.4 to types 6B a nd 19F, respectively, The mean infant/maternal antibody ratios were 0. 56 and 0.59 (range 0.11-1.46) for these serotypes. Infant cord antibod y titres correlated with maternal titres, Infant/maternal IgG ratios c orrelated with the interval between immunisation and birth and were hi gher for specific IgG1 than for IgG2. infants of pneumococcal vaccine recipients had geometric mean antibody concentrations of 6.8 and 7.5 m u g/mL to serotypes 6B and 19F in cord blood; in cord blood and in all subsequent serum specimens the concentrations were 2-3 fold higher th an in control infants, The median half-life of passive antibody was ab out 35 days; at five months of age 63-71% of infants of pneumococcal V accine recipients had antibody concentrations greater than 0.15 mu g/m L. Breast milk IgA antibodies for pneumococcal serotype 19F, but. not for type 6B, were significantly higher in vaccine recipients up to fiv e months after delivery. If maternal pneumococcal polysaccharide antib odies do not interfere with active immunisation of the infant with new glycoprotein conjugate pneumococcal vaccines, passive-active immunisa tion of infants can be a feasible strategy for developing regions.