Immunogenicity and safety of two doses of live attenuated varicella vaccine for children

Objective To evaluate the immunogenicity and safety of an immunization strategy with two doses of live attenuated varicella vaccine. Methods A total of 958 children aged 1.5 to 7 years were recruited from Henan province and divided into four groups based on the length of interval between two injections (3 months, 1 year, 3 years and 5 years). Serum samples were collected from each individual before and 35 to 42 days after the second immunization for the detection of antibodies against varicella-zoster virus by antibody membrane immune-fluorescence assay. Results The levels of antibodies in serum samples from all groups declined over time since the first dose immunization of varicella vaccine. Significant differences with the geometric mean titers (GMT) of antibodies were found among different groups by statistical analysis of variance (F=39.690, P<0.05). Results of the Wilcoxon signed-rank test showed that there were significant differences with the GMT of antibodies in all subjects before and after the second dose immunization with varicella vaccine (all P<0.01). The adverse events were observed in 10.4% (100/958) of immunized children within 14 days after the second vaccination. Of the adverse events, fever accounted for 6.99% and local swelling took 1.15%, no other adverse events were observed. Conclusion Immunization of children with two doses of live attenuated varicella vaccine showed the advantages of good immunogenicity and safety. The immunization strategy with two doses of varicella vaccine should be proposed in our country as soon as possible. Key words: Live attenuated varicella vaccine; Two-dose; Immunogenicity; Safety