Ineffectiveness for infants of immunization of mothers with pneumococcal capsular polysaccharide vaccine during pregnancy.

Pneumococcal (Pnc) carriage is associated with pneumococcal diseases. Breast feeding and maternal vaccination may be a useful approach to prevent pneumococcal infection in young infants. We examined the risk of Pnc carriage by infants at six months of age after pneumococcal polysaccharide vaccination of pregnant women. We selected 139 pregnant woman. The woman were randomly allocated to receive 23-valent polysaccharide vaccines during pregnancy (Group 1) after pregnancy (Group 2) or not receive any vaccine (Group 3). Nasopharyngeal swabs were collected from the infants at three and six months of age. The infants were evaluated monthly during the first six months. We included 47 mothers in Group 1, 45 mothers in Group 2 and 47 mothers in Group 3. Forty-seven percent of the babies were exclusively breast fed until six months, 26% received both breast feeding and artificial feeding and 13% received only artificial feeding. Among those patients, 26% were colonized by Pnc at six months (12 from Group 1, 13 from Group 2, and 12 from Group 3). There was no significant difference in colonization between the three groups. Thirty percent of the children were colonized by a non-susceptible strain. We concluded that young infants (three months old) are already susceptible to pneumococcal carriage. Vaccination during pregnancy with a polysaccharide vaccine did not decrease Pnc colonization.