Survey of Rates of Healthy Carriers of N. Meningitidis and Characterisation of Circulating Strains

Abstract

METHOD: Healthy carriers in the population at large: cross survey performed between March and May 1998, among residents in Extremadura. We took two age groups: 0-19 years of age, vaccinated (n=1,140) and 20 years of age and over (n=1,193), unvaccinated. Healthy carriers in a military barracks: cross survey on a military base in May 1998 (n=619), taking two groups: < 20 years of age (n=453) vaccinated, and 20 years of age and over (n=166) unvaccinated. RESULTS: Healthy carrier in the population at large. The percentage of carriers for all of the serogroups was: 0-19 years of age 7.98, 20 years of age and older 3.32, total 4.60, for serogroup B: 4.43, 2.25 and 2.84; for C: 0.04, 0.10 and 0.08 respectively. The differences between the two age groups in serogroup B and the total are statistically significant, as well as the greater prevalence of B over C. The subtype of the three samples with isolation of serogroup C was: one strain NT:P1.6, another strain 2b:P1.2, and one that could not be sub-typed. A strain that could not be classified into a serogroup was sub-typed as 2b: P1. 5. Healthy carriers in a military barracks. The percentage of carriers for all of the serogroups was: < 20 years 8.43, 20 years of age and over 6.84, total 7.27, for serogroup B: 4.82, 3.75 and 4.04; and for C: 0.60, 0.00 and 0.16 respectively. The higher prevalence obtained in military subjects in comparison with the population at large revealed statistically significant differences. Also, the prevalence of serogroup B was significantly higher than C. The only isolated C strain was sub-typed as: p1.2,5. CONCLUSIONS: The prevalence of healthy carriers of N. meningitidis in the population at large was 4.60 %, being higher in the lower age group and the barracks. Very low prevalence of serogroup C. Impossible to conclude that the strain N. meningitidis serogroup C was circulating during the 1.997/98 season.