Secondary Attack Rates in Primary and Secondary School Bubbles Following a Confirmed Case: Active, Prospective National Surveillance, November to December 2020, England

Abstract

Background: Following the full re-opening of schools in England and emergence of the SARS-CoV-2 Alpha variant, we investigated the risk of SARS-CoV-2 infection in students and staff who were contacts of a confirmed case in a school bubble (school groupings with limited interactions), along with their household members.

Methods: Primary and secondary school bubbles were recruited into sKIDsBUBBLE after being sent home to self-isolate following a confirmed case of COVID-19 in the bubble. Bubble participants and their household members were sent home-testing kits comprising nasal swabs for RT-PCR testing and whole genome sequencing, and oral fluid swabs for SARS-CoV-2 antibodies.

Results: During November-December 2020, 14 bubbles were recruited from 7 schools, including 269 bubble contacts (248 students, 21 staff) and 823 household contacts (524 adults, 299 children). The secondary attack rate was 10.0% (6/60) in primary and 3.9% (4/102) in secondary school students, compared to 6.3% (1/16) and 0% (0/1) among staff, respectively. The incidence rate for household contacts of primary school students was 6.6% (12/183) and 3.7% (1/27) for household contacts of primary school staff. In secondary schools, this was 3.5% (11/317) and 0% (0/1), respectively. Household contacts were more likely to test positive if their bubble contact tested positive although there were new infections among household contacts of uninfected bubble contacts.

Interpretation: Compared to other institutional settings, the overall risk of secondary infection in school bubbles and their household contacts was low. Our findings are important for developing evidence-based infection prevention guidelines for educational settings.

Note: Funding: This surveillance was funded by the Department of Health and Social Care (DHSC) and Public Health England (PHE).

Declaration of Interests: None.

Ethics Approval Statement: This investigation was undertaken as part of PHE’s duty, provided by Regulation 3 of The Health Service (Control of Patient Information) Regulations 2002 to (a) diagnose communicable diseases and other risks to public health; (b) recognise trends in such diseases and risks; (c) control and prevent the spread of such diseases and risks; and (d) monitor and manage outbreaks of communicable disease and incidents of exposure to communicable disease. Participants were considered recruited once they provided online consent and completed the online questionnaire. Participants were also asked obtain consent from other household members. Parents gave consent for their children all students (aged <16 years) Other household members also provided consent. All consent was undertake online using the snapsurvey questionnaire platform. Participants could not be recruited unless they provided online consent (adults for themselves, parents for children) and completed an online recruitment questionnaire

Keywords: COVID-19; SARS-CoV-2; Schools; Transmission; Contacts; Testing; Secondary Attack Rate