Lack of correlation between school reopening and trends in adult COVID-19 hospitalisations and death rates during the Delta and early Omicron periods: an ecological analysis of five countries

Objectives: In this ecological study, we describe SARS-CoV-2 case incidence for school age and adult populations, COVID-19 hospitalisation and death rates during Delta and the early Omicron periods, before and after schools reopened in five countries.

Methods: Data were extracted from government websites. Cases and COVID-19 hospitalisation and death incidence rates were calculated during the Delta and early Omicron periods in Australia, Canada, Denmark, Finland and the United Kingdom, for two weeks preceding and six weeks after schools reopened. We summarised stringency of public health measures (GRI), vaccination by age and testing rates.

Results: During Delta, cases increased in 2/7 sites after schools reopened, hospitalisations increased in 1/5 sites, while deaths decreased in one and increased then decreased in another. During Omicron, cases increased in 2/8 sites, hospitalisations increased in 1/6 sites and deaths increased in 1/4 sites. The hospitalisation and death rate trends that commenced before schools reopened continued on the same trajectory after schools reopened. Vaccination rates in ≥70-year-olds were 75-100% during Delta and 95-100% during Omicron. Wide variations in testing rates may explain differences in case incidence. GRI were higher during Delta with more variation than during Omicron.

Conclusions: Reopening schools did not change the existing trajectory of COVID-19 rates.