Seroconversion and Duration of Immunity following a Vaccination Campaign against N. Meningitidis Serogroup

Abstract

BACKGROUND: An increase in the incidence of meningococcal disease in the Region of Murcia during the 1996/97 season led the General Directorate for Health to carry out a Vaccination Campaign against the serogroup C meningococcus in September-October 1997. The purpose of this study was to ascertain the percentage of children under 5 years of age who ration, and the percentage who retained immunity after one year. METHOD: The monitoring of 296 children between 18 and 59 months of age. The serological determinations were performed prior to vaccination, one month following vaccination and after one year. The antibody titres were determined according to a "bactericidal test" in the Center for Disease Control. RESULTS: Of the 296 children studied, only 11 (3.7%) revealed bactericidal antibody titres prior to vaccination. After one month, of the children who did not show antibodies prior to vaccination, 167 (63.7%) seroconverted. A statistically significant linear tendency (p<0.001) of increase in the percentage of seroconversion in relation to the vaccination age was observed. One year after vaccination, from among the children seroconverted one month following vaccination, only 6 (4.3%) revealed bactericidal antibodies. CONCLUSION: The percentage of seroconversion in children under 5 years of age, following administration of the capsular polyssacharide C vaccine, was seen to clearly increase with the age of the subjects. The seroprotection acquired in vaccinated children declined quickly during the year following vaccination.