Meningococcal antibody titres in infants of women immunised with meningococcal polysaccharide vaccine during pregnancy

Seventy five Gambian women were immunised with a single dose of a group A+group C meningococcal polysaccharide vaccine during the last trimester of pregnancy. IgG antibody titres were measured in mothers and in their infants by an enzyme-linked immunosorbent assay (ELISA). All women had a good response to vaccination and maternal antibodies were high at the time of delivery (23.2 mu g/ml for group A antibodies and 14.3 mu g/ml for group C antibodies). only a proportion of However, antibody crossed the placenta; blood:maternal antibody ratios were 30% for group A antibody and 44% for group C antibody, respectively. Considerable variability in cord blood:maternal blood ratios was seen between individuals. This could not be related to age, parity, or ethnic group. Mean group A and group C cord blood:maternal blood ratios were lower in women with serological evidence of syphilis than in seronegative women, and diminished transfer of group A antibody was noted in women with active malarial infection of the placenta. Antibody titres declined rapidly in infants and by the age of 3-4 months these had reached control values. Maternal immunisation may give infants some protection against group A and group C meningococcal disease but only during the first few months of life.