SARS-CoV-2 infection and transmission in educational settings: a prospective, cross-sectional analysis of infection clusters and outbreaks in England

Abstract

Background: Understanding severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection and transmission in educational settings is crucial for ensuring the safety of staff and children during the COVID-19 pandemic. We estimated the rate of SARS-CoV-2 infection and outbreaks among staff and students in educational settings during the summer half-term (June-July, 2020) in England.

Methods: In this prospective, cross-sectional analysis, Public Health England initiated enhanced national surveillance in educational settings in England that had reopened after the first national lockdown, from June 1 to July 17, 2020. Educational settings were categorised as early years settings (<5-year-olds), primary schools (5-11-year-olds; only years 1 and 6 allowed to return), secondary schools (11-18-year-olds; only years 10 and 12), or mixed-age settings (spanning a combination of the above). Further education colleges were excluded. Data were recorded in HPZone, an online national database for events that require public health management. RT-PCR-confirmed SARS-CoV-2 event rates and case rates were calculated for staff and students, and direction of transmission was inferred on the basis of symptom onset and testing dates. Events were classified as single cases, coprimary cases (at least two confirmed cases within 48 h, typically within the same household), and outbreaks (at least two epidemiologically linked cases, with sequential cases diagnosed within 14 days in the same educational setting). All events were followed up for 28 days after educational settings closed for the summer holidays. Negative binomial regression was used to correlate educational setting events with regional population, population density, and community incidence.

Findings: A median of 38 000 early years settings (IQR 35 500-41 500), 15 600 primary schools (13 450-17 300), and 4000 secondary schools (3700-4200) were open each day, with a median daily attendance of 928 000 students (630 000-1 230 000) overall. There were 113 single cases of SARS-CoV-2 infection, nine coprimary cases, and 55 outbreaks. The risk of an outbreak increased by 72% (95% CI 28-130) for every five cases per 100 000 population increase in community incidence (p<0·0001). Staff had higher incidence than students (27 cases [95% CI 23-32] per 100 000 per day among staff compared with 18 cases [14-24] in early years students, 6·0 cases [4·3-8·2] in primary schools students, and 6·8 cases [2·7-14] in secondary school students]), and most cases linked to outbreaks were in staff members (154 [73%] staff vs 56 [27%] children of 210 total cases). Probable direction of transmission was staff to staff in 26 outbreaks, staff to student in eight outbreaks, student to staff in 16 outbreaks, and student to student in five outbreaks. The median number of secondary cases in outbreaks was one (IQR 1-2) for student index cases and one (1-5) for staff index cases.

Interpretation: SARS-CoV-2 infections and outbreaks were uncommon in educational settings during the summer half-term in England. The strong association with regional COVID-19 incidence emphasises the importance of controlling community transmission to protect educational settings. Interventions should focus on reducing transmission in and among staff.

Funding: Public Health England.

Figure 1

Trends in confirmed adult and paediatric case numbers and rates per 100 000 population (A) and time series of confirmed cases disaggregated by setting (B), in the context of alert level and measures in place (C) in England, June–July, 2020 All statistics are reported by week. (A) Paediatric cases are in children and adolescents up to the age of 18 years. (C) COVID-19 alert levels correspond to the national-level system then in place in England; level 3 corresponded to relaxed physical distancing measures in a context where severe acute respiratory syndrome coronavirus 2 is in general circulation, whereas level 4 corresponded to enforced physical distancing in a context of high levels of transmission. Changes in travel restrictions during this period refer to the introduction of international travel corridors to a list of exempted countries, with no requirement for arriving passengers to self-isolate.

Figure 2

Data flow through to the analysis phase The number of open settings at the head of the flowchart is a daily figure (with a mean number of open settings provided for the period June 1–July 17, 2020); event and case numbers are totals for the whole period. HPT=Health Protection Team. *17 settings for mixed age groups were excluded from event rate calculations because denominators were not available.

Figure 3

Associations between number of outbreaks and regional COVID-19 incidence (A), regional population (C) and population density (E), and equivalent plots for single confirmed cases (B, D, F) Trend lines are given only where significant results were obtained from negative binomial regression: for the number of confirmed outbreaks in educational settings versus COVID-19 regional incidence (panel A); and for the number of confirmed cases versus regional population density (panel F). RRs are given to two significant figures. RR=rate ratio.

Figure 4

Summary of outbreaks by the type of educational setting in which they were reported, and likely direction of transmission between staff and students Blue boxes highlight the setting type, red boxes highlight the likely direction of transmission from the index case, and green boxes indicate the subset of outbreaks in which mass swabbing was done (ie, testing of contacts but also wider staff and students at the setting).