A cross-sectional national investigation of COVID-19 outbreaks in nurseries during rapid spread of the Alpha (B.1.1.7) variant of SARS- CoV-2 in England

Background: In England, the emergence the more transmissible SARS-CoV-2 variant Alpha (B.1.1.7) led to a third national lockdown from December 2020, including restricted attendance at schools. Nurseries, however, remained fully open. COVID-19 outbreaks (≥ 2 laboratory-confirmed cases within 14 days) in nurseries and assess the risk of SARS-CoV-2 infection and incidence rates in staff and children over a three-month period when community SARS-CoV-2 infections rates were high and the Alpha variant was spreading rapidly across England. Methods This was a cross-sectional national investigation of COVID-19 outbreaks in nurseries across England Nurseries reporting a COVID-19 outbreak to PHE between November 2020 and January 2021 were requested to complete a questionnaire about their outbreak. Results 324 nurseries, comprising 1% (324/32,852) of nurseries in England, reported a COVID-19 outbreak. Of the 315 (97%) nurseries contacted, 173 (55%) reported 1,657 SARS-CoV-2 cases, including 510 (31%) children and 1,147 (69%) staff. A child was the index case in 45 outbreaks (26%) and staff in 125 (72%) outbreaks. Overall, children had an incidence rate of 3.50% (95%CI, 3.21–3.81%) and was similar irrespective of whether the index case was a child (3.55%; 95%CI, 3.01–4.19%) or staff (3.44%; 95%CI, 3.10–3.82%). Among staff, incidence rates were lower if the index case was a child (26.28%; 95%CI, 23.54–29.21%%) compared to a staff member (32.98%; 95%CI, 31.19–34.82%), with the highest incidence rate when the index case was also a staff member (37.52%; 95%CI, 35.39–39.70%). Compared to November 2020, outbreak sizes and incidence rates were higher in January 2021, when the Alpha variant predominated. Nationally, SARS-CoV-2 infection rates in < 5 year-olds remained low and followed trends in older age-groups, increasing during December 2020 and declining thereafter. Conclusions In this cross-sectional study of COVID-19 outbreaks in nurseries, one in three staff were affected compared to one in thirty children. There was some evidence of increased transmissibility and higher incidence rates associated with the Alpha variant