Immune response to revaccination with meningococcal A and C polysaccharides in Gambian children following repeated immunisation during early childhood

Forty-two Gambian children randomised to receive two doses of meningococcal A/C polysaccharide vaccine (MPS) in infancy and either MPS (n = 15), menin gococcal A/C conjugate (n = 13) or inactivated polio vaccine (IPV n = 14) a t 2 years, were revaccinated with MPS at 5 years of age along with 39 match ed control children. Meningococcal A and C polysaccharide antibodies were a nalysed by ELISA and bactericidal assay (SBA) in sera taken before and 10 d ays after revaccination. The geometric mean group SEA titre in the MPS grou p following revaccination was about half that of the unvaccinated controls (0.51 95%CI: 0.28, 0.90) for group A and less than half that of the control s for group C (0.41, 95%CI: 0.16, 1.03 P = 0.06). The group C SEA response in the conjugate group was 14-fold higher than in the MPS group (P < 0.001) , Multiple doses of meningococcal polysaccharide in childhood may therefore attenuate the SEA response to both group A and group C polysaccharides. In contrast, vaccination with meningococcal A/C conjugate after MPS in infanc y gives immunological memory to N. meningitidis group C. (C) 1999 Published by Elsevier Science Ltd. All rights reserved.