Studies on epidemics of influenza--relationship between the closure of some or whole classes of the school and the time or rate of inoculation with influenza vaccine.

Abstract

Summary A survey was conducted on the closure of some or whole classes of a grade in 66 primary and lower secondary schools operated by the Ward of Suginami, Tokyo, during the epidemic period of influenza-like disease in four years, 1979 to 1982. Therefore, the cumulative number of schools surveyed was 264 for the four years. In these schools was surveyed the relationship between the class closure in 1979-1983 and the time of inoculation of influenza vaccine or the rate of inoculation. The results obtained are summarized as follows. 1) In the 264 schools, the second inoculation of influenza vaccine was finished in 203 schools (76.8%) in November and in 61 schools (23.2%) in December. The closure of some or whole classes of a grade occurred in 125 schools (61.6%) of the former 203 schools and in 20 schools (32.7%) of the latter 61 schools. Accordingly, it took place significantly more frequently (p<0.001) in the former than in the latter. 2) Of the 264 schools, 145 schools (54.9%) experienced class closure (group C), but the other 119 schools (45.1%) did not (group N). The average rates of the first and the second inoculation were 86.7% and 77.3%, respectively, in group C and 88.0 and 78.9%, respectively, in group N. Therefore, the average rate of the second inoculation was significantly lower (p<0.01) than that of the first inoculation in both groups. 3) The interval between the two inoculations was 8-14 days in 136 schools (51.5%) and 15-21 days in 90 schools (34.1%) of the 264 schools. From the results mentioned above it was concluded to be necessary for the further enhancement of the immune effect of the existing HA vaccine to make the interval between the first and the second inoculation 4 weeks, to perform the second inoculation about one month prior to the beginning of an epidemic period (from the end of January to that of February), and to increase the rate of the second inoculation.