Fig. 1

Comparison of morbidity between the vaccinated and unvaccinated groups. In elementary school students, morbidity in the vaccinated group was significantly lower during the 10-year period, except during 2012–2013, 2014–2015, and 2019–2020. Among middle school students, morbidity was higher among the vaccinated students every year. A consistent trend in morbidity was lacking among faculty and staff.