[Study on the immunogenicity and safety of recombinant B-subunit/whole cell cholera vaccine infused with antacids in healthy population at ages of 2-6 years].

Objective: To assess the immunogenicity and safety of recombinant B-subunit/whole cell cholera vaccine (rBS/WC) oral cholera vaccine (Ora Vacs) infused with antacids in healthy population at ages of 2-6 years. Methods: Between December 2009 and January 2010, we recruited 900 volunteers aged 2-6 years od through giving out recruitment notice for the eligible children's parents from different vaccination clinics of Chongzuo city in Guangxi Zhuang Autonomous Region. This study was a randomized, double-blind, placebo-controlled trial, and subjects were randomly (2∶1) assigned to receive Cholera vaccine infused with antacids or placebo, and observed for safety. Serum samples of 300 subjects in immunogenicity subgroups (200 for vaccine groups, 100 for control groups) before the 1st dose and 49 d (±3 d) after immunization were collected, and determined for antibody levels against the cholera toxin (anti-CT) and cholera vibriocidal (anti-Vab) with Enzyme-linked immunosorbent assays (ELISA), based on which the GMT was calculated. There were 266 cases paired with the serum samples before and after immunization (177 for vaccine groups, 89 for control groups). The comparison of subjects' age at enrollment and the level of GMT before and after immunization between groups were analyzed by t test. The superiority test for the difference between seroconversion rates of vaccine groups and control groups were analyzed by χ(2) test. Results: Of 900 subjects enrolled, the number of males and females were 503 and 397 respectively (vaccine groups 335 vs. 265, control groups 168 vs. 132), the average ages of vaccine groups and control groups at enrollment were (4.8±1.2) years and (4.9±1.2) years respectively. There were no significant differences between groups in terms of gender and age (χ(2)=0.00, P=1.000; t=0.55, P=0.585). The 2 times increase rates of anti-CT and anti-Vab in vaccine groups after inoculation were 90.96% and 57.63% respectively, which were superiority to those of control groups (15.73% and 29.21%), and significant differences were observed between groups (χ(2)=15.89, χ(2)=3.85, P<0.001). There were significant differences between vaccine groups and control groups after inoculation in terms of GMTs of anti-CT (1∶647.56 vs. 1∶99.49) and anti-Vab antibodies (1∶16.19 vs. 1∶11.27) (t values were 15.82 and 3.43, respetively; both P values were<0.05), significant differences were observed in the growth rates when compared the GMTs of anti-CT (6.63 vs. 1.11) and anti-Vab antibodies (1.64 vs. 1.16) before inoculation between vaccine groups and control groups (t'=17.85 and 4.96, P<0.001). In terms of safety, the adverse reaction rates in vaccine groups and control groups were 37.67% (226/600) and 36.67% (110/300), respectively,the common adverse reaction including fever, nausea, vomiting, abdominal pain, diarrhea, headache, fatigue, allergies, rash, etc; and the severity degree were mainly for level 1. Conclusion: Ora Vacs infused with antacids could produce an positive effect on immune response and safety.