Study on the effects of influenza virus vaccines--relation between the rate of two-fractional vaccination and the overall rate of absenteeism

Abstract

In 1987 and 1988, in 9 elementary schools, the percentage of children who received two sessions of vaccination and the overall rate of absenteeism resulting from influenza were determined for each class, and their relationship was investigated. The following results were obtained. 1) The mean vaccination rate was 58.6% among 157 classes in 1987, whereas it was 29.9% among 151 classes in 1988, the rate being significantly higher in 1987. 2) The mean overall rate of absenteeism was 1.524% in 1987, which was significantly lower than the corresponding rate, 2.802%, in 1988. 3) There was a significant negative correlation between the vaccination rate and the overall rate of absenteeism in 7 of the 9 schools in 1987; the overall rate of absenteeism became significantly low with an increase in the vaccination rate. 4) No such trend, however, was noted in any of the schools in 1988. 5) The difference between the results in 1987 and those in 1988 seems to be attributable to the facts that variability of the prevailing strains of influenza was low (V0, 82%) in 1987, in addition to the high vaccination rate in that year, and that influenza virus type B having a high variability (V3, or more, 78%) prevailed in 1988, when the vaccination rate was low.