Impact of meningococcal vaccination with combined serogroups A and C polysaccharide vaccine on carriage of Neisseria meningitidis C.

Two studies of meningococcal carriage state were carried out in Galicia (Spain) before and after a mass vaccination campaign between December 1996 and January 1997 against Neisseria meningitidis serogroup C with meningococcal serogroups A and C polysaccharide vaccine. The studies covered two areas with different incidence rates of meningococcal disease in 1996 (high and low incidence). Carriage rates of serogroup C showed a decrease in both areas, 47 and 65 % respectively, before and after the vaccination. Results showed a decrease in carrier state in the age groups 10-14- and 15-19-year-olds, but not in the 5-9-year-olds. These results demonstrate the effect of immunization on the reduction of the carriage state.