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

To evaluate the epidemiological effects of vaccine immunization program related to A (H1N1) influenza in the middle school students.

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.

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).

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.