London School of Hygiene & Tropical Medicine

The findings from the second round of testing by the Schools Infection Survey (SIS), carried out in schools over December 2020, suggests the proportion who were positive for COVID-19 infection among participating staff and students on site was lower than the surrounding community, and antibody tests showed no evidence to indicate participating school staff are at greater risk of infection.

The report confirms schools are working hard to prevent COVID-19 infections occurring on their sites, although transmission remains an important risk that needs continued efforts and careful monitoring as schools re-open fully.

SIS is jointly led by researchers from the London School of Hygiene & Tropical Medicine (LSHTM), Public Health England (PHE) and the Office for National Statistics (ONS), and is funded by the Department for Health and Social Care (DHSC). It aims to examine the prevalence of current infection and antibodies for SARS-CoV-2 among staff and students, monitor COVID-19 related absences, and assess implementation of measures by schools to control the virus, through valuable collaboration between scientists, school staff, pupils and parents.

In round two, 7,089 students and 5,114 staff in 121 schools (41 primary and 80 secondary) from 15 local authority areas were tested at least once in December 2020, when schools were still open. They were tested for both the presence of the virus using nasal swab PCR tests, and antibodies (through blood samples from staff and saliva swab samples from students).

They found that the proportion of staff who tested positive for COVID-19 antibodies, which indicate a past infection, was 14.6% of primary staff, compared to 15.7% of secondary staff.

The prevalence of antibodies in school staff was similar to that of working age adults in the local community, and no evidence was found to suggest that school staff were at significantly higher risk of infection.

Currently, antibody data for students are only available for round one. During testing in November 2020 in primary schools, 12.63% of staff and 7.65% of students tested positive for antibodies, compared to 12.27% of staff and 10.95% of students in secondary schools. However, staff and students used different tests, so cannot be directly compared.

There has been a huge effort by schools to implement a number of COVID-19 control measures to ensure the safety of their staff and students from infection entering the school site and prevent transmission within their sites.

The survey found that schools in this study implemented measures including ensuring symptomatic individuals or contacts of infected individuals stayed at home, enhanced cleaning and hygiene protocols, limiting gatherings of students and staff, and staff distancing from other adults. Schools have also implemented ‘bubble systems’, with primary schools focusing on social distancing between bubbles, while secondary schools also implemented measures to limit contact between individuals within the same bubble.

Dr Shamez Ladhani, Consultant Paediatrician at PHE and the study’s chief investigator, said: “These results confirm the findings of our previous studies, including sKIDs, which showed low rates of COVID-19 antibody positivity among staff and students in schools.

“We found that those attending schools had similar rates of antibody positivity to people of the same age in the community, which indicates that staff and students in schools are not at a significantly higher risk of COVID-19 than the general population.”

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Professor Sinéad Langan, co-chief investigator of the study at LSHTM, said: “Schools and their staff have made a huge effort to protect themselves and their students by implementing COVID-19 control measures to try and stop infection entering the school site, and reduce on-site transmission. These preliminary findings suggest participating school staff were not at significantly higher risk of infection than working age adults in the wider community.”

Looking at current infections on the day of testing, the researchers found that in both round one and round two, a lower proportion of students and staff in primary schools tested positive for current infection than those in secondary schools. Over the two rounds, 1.64% of staff and 1.22% of pupils in secondary schools tested positive, whilst in primary schools 0.99% of staff and 0.94% of students tested positive.

However, the 95% confidence intervals indicate that these differences between pupils and staff and primary and secondary schools were not statistically significant.

Professor Langan added: “With every round of this study we are finding out more about COVID-19 infection in schools, and how that links with transmission in the local community. These findings show that some individuals attending schools have COVID-19 infections and therefore there is potential for transmission. However, it is still hard to say whether this infection is occurring within the schools or in the wider community.

“More investigation is needed to measure the tangible effect of school control measures implementations. The effect of the recently introduced twice weekly home tests on infection prevalence within schools should also be carefully evaluated.”

The researchers emphasise that these findings do not include individuals who were self-isolating during surveillance, and are affected by a low response rate, particularly in students, so should be interpreted with caution. Individuals who agree to participate may be different from those who do not sign up.

The researchers are hopeful that, as the SIS study continues, they will learn more about school outbreaks, the impact of testing asymptomatic individuals, and the role of schools in COVID-19 transmission within the wider community to ensure a safe return to education for staff and students.

Fiona Dawe, Deputy Director, Schools Infection Studies, said: “The Schools Infection Survey is providing us with valuable insight into how COVID-19 is transmitted in school settings.

“We are seeing slightly higher numbers of infections in secondary schools than in primary schools, however the difference is not statistically significant.

“Similarly, the prevalence of antibodies in school staff was similar to that of working age adults in the local community. We found no evidence of a statistical difference in the infection risk for school staff.

“I’d like to thank all of the staff, pupils and parents involved in our study for their continued support and commitment in helping us gather this vital information.”

LSHTM co-investigators from the Faculty of Epidemiology and Population Health and the Faculty of Public Health and Policy were jointly involved in the design and analysis of this study.

The researchers note that the data collected in this study is not representative of all schools in England. The study design (which over-samples schools in areas of England where COVID-19 infection was highest at the start of the academic year) means the data presented are not intended to be generally applicable to all schools. Test results are only available for those who enrolled in the survey and were present on-site on the day of testing, and the findings are estimates. 

Publication

COVID-19 Schools Infection Survey Round 2, England: December 2020.