Prospective observation of breakthrough cases and analysis of antibody dynamic changes after two doses of varicella / 中华预防医学杂志

ABSTRACT

Objective: To investigate the breakthrough rate and antibody level of children vaccinated two doses varicella vaccine in Tianjin city, and to compare them with those vaccinated one dose. Methods: A total of 1 112 children who were vaccinated two doses varicella vaccine were selected as the experimental group. According to the same street and township, children who had received only one dose within one year of age difference, and whose first injection time was less than one month from the first dose of varicella vaccine in the experimental group were selected as the control group. A three-year prospective observation was conducted on the incidence of varicella in the two groups. 108 pairs of children in the two groups were selected to collect antivaricella serum in the first to third year. The rate of breakthrough cases, antibody level and antibody positive rate were compared by χ2 test, t-test and variance analysis between and within the two groups in three years. Results: The cumulative breakthrough rate of the experimental group was 0.54%(6/1 112), which was lower than that of the control group 3.96% (44/1 112, χ²=29.544, P<0.001). The GMC level of antibody in the experimental group decreased year by year (F=18.291, P<0.001), and the GMC level in the control group also decreased year by year (F=91.383, P<0.001). There was significant difference in GMC level between the two groups (P<0.001). The difference of antibody positive rate in the experimental group was statistically significant in three years (χ²=11.107, P<0.01), there was significant difference in the positive rate between the first year and third year (P<0.01), there was no significant difference in the positive rate of the control group in three years (χ²=3.351, P>0.05). The positive rate of the experimental group was higher than that of the control group (P<0.001). Conclusion: Two doses varicella vaccine can significantly improve the antibody level and positive rate, but it still shows a downward trend with the extension of time. It is necessary to consider strengthening immunization according to the actual situation.