[Efficacy of influenza vaccination and its relationship to daily absentee rate]

To determine the efficacy of influenza vaccination and it's relationship to "daily physical condition", an investigation was carried out in two elementary schools and one junior high school. Since children who had many absences during the first and second trimesters, tend to have many absentee days in the third trimester and during the last year, also, absentee rate during the first and second trimesters was considered to be an indicator of "daily physical condition". Vaccinated children tended to have lower absentee rates than nonvaccinated children during the first and second trimesters. This indicates that there is a definite difference between vaccinated and nonvaccinated children in terms of "daily physical condition". Children who had many absences during the first and second trimesters, also tended to have many absentee days during the influenza season, introducing a confounding factor, "daily physical condition", when comparisons are made in the absentee rate between vaccinated and nonvaccinated children during the influenza season. Careful analysis of these data, taking into account their "daily physical condition", showed that vaccinated children tended to have lower absentee rates than the nonvaccinated during the influenza season. However there was no definite difference between vaccinated and nonvaccinated children in length of absentee days during the influenza season.