[Analysis for protection rate and antibody levels of epidemic cerebrospinal meningitis among children aged between 3-23 months in Liuzhou, in 2012].

To understand the level of bactericidal antibodies against and their rate of protection in children aged between 3 and 23 months, in Liuzhou, in 2012. Convenience sampling was performed in Liujiang, Rong'an and Sanjiang Counties from May through August, 2012. The inclusion criteria for 603 subjects were: Children aged between 3 and 23 months; no history of meningococcal meningitis; no vaccination against serogroup C; more than 30 days from the last vaccination against serogroup A. Demographic information and immunization history of the subjects were obtained using questionnaires. Venous blood samples (2.0 ml each) were collected and levels of antibodies determined using a Serum Bactericidal Assay (SBA). The geometric mean titer (GMT) of serum bacterial antibodies was positive when it was greater than or equal to 1∶2 and protective when greater than 1∶8. Chi-square and Fisher's exact tests were used to compare differences in the positive and protective rates of serum antibodies of serogroup A and serogroup C, among children with different demographic characteristics. Kruskal-Wallis test was used to compare differences in the GMT of serum antibodies of serogroup A and serogroup C, among children with different demographic characteristics. Of 603 subjects, 325 (53.9%) were female and 278 (46.1%) were male; 276 (45.8%), 143 (23.7%) and 184 (30.5%) subjects were administered, respectively, no treatment, 1 dose vaccine and 2 doses vaccine. The GMT of serum antibodies against group A was 1∶1.11, the positive rate was 7.6% (46) and the protective rate was 2.0% (12). The GMT of antibodies in children receiving 1 vaccine dose was 1∶1.16 and the protective rate was 3.5% (5), both values higher than those in children receiving 2 vaccine doses (GMT: 1∶1.2, protective rate: 3.5% (5)). However, these differences were not statistically significant (GMT: =0.64, 0.728; protective rate: Fisher's exact test, 0.080). The GMT of antibodies in children receiving 1 and 2 doses of vaccines were 1∶1.12 and 1∶2.30, respectively (≤180 d). The GMT of serum antibodies for group C vaccine was 1∶1.18 and its positive and protective rates were 14.6% (88) and 2.2% (13), respectively. Children aged between 3 and 23 months are susceptible to groups A and C. The immune effectiveness of group A vaccine is relatively poor in this age group and their antibody levels decreased rapidly.