[Epidemiological effects of the A (H1N1) influenza vaccine immunization program on students].

ABSTRACT

OBJECTIVE: To evaluate the epidemiological effects of vaccine immunization program related to A (H1N1) influenza in the middle school students. METHODS: Non-randomized clinical trial was designed to assess the A (H1N1) influenza vaccine on its efficacy. 14 883 students from 8 middle schools in Zhejiang province were recruited and classified into vaccinated or control groups, based on the status of immunization with A (H1N1) influenza vaccine. All subjects were followed up through one epidemic period (6 months) and the incidence rates of influenza-like illnesses, A (H1N1) influenza, and seasonal influenza in these two groups were compared to evaluate the efficacy of the vaccine. RESULTS: There were 6334 subjects in the vaccinated group and 8549 in the control group. 7441.75 person-years were followed from these two groups. The incidence rate of A (H1N1) influenza in vaccinated group was 1.64‰ per person-year, lower than that of the control group. The rate difference (RD) was -1.64‰ per person-year (95% confidence interval value from -3.04‰ to -0.23‰ per person-year), and the difference was significant (P = 0.010). The incidence rate of influenza-like illnesses in vaccinated group was 21.47‰ per person-year, lower than that of the control group (22.69‰ per person-year) and the difference was not significant (P > 0.05). The incidence rate of B influenza in vaccinated group was 6.63‰ per person-year, higher than that of control group (7.02‰ per person-year) but the difference was not significant (P > 0.05). CONCLUSION: This vaccine demonstrated a good epidemiological effect against the A (H1N1) influenza virus infection, observed through a student-immunization program. The cross-protection effect against the influenza-like illnesses and other seasonal influenzas was not noticed in this study.