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Covid-19: School staff testing positive for antibodies rose to around 15% in December

BMJ 2021; 372 doi: https://doi.org/10.1136/bmj.n598 (Published 01 March 2021) Cite this as: BMJ 2021;372:n598

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  1. Elisabeth Mahase
  1. The BMJ

The proportion of school staff testing positive for antibodies against SARS-CoV-2 rose from 12.63% to 14.61% for primary staff and from 12.27% to 15.72% for secondary staff between November and December, the latest results from the Schools Infection Survey have shown.

For the second round of the survey—which is run by the London School of Hygiene and Tropical Medicine, Public Health England, and the Office for National Statistics—staff and pupils were tested at 121 schools (41 primary, 80 secondary) across 15 local authorities for current and past infection. A total of 12 204 participants (5114 staff and 7089 pupils) had at least one test between 2 and 10 December 2020.1

The report found that a slightly lower percentage of primary pupils and staff tested positive for covid-19 (0.94% and 0.99%, respectively) than of secondary pupils and staff (1.22% and 1.64%). The percentage of staff testing positive for antibodies against SARS-CoV-2 also increased between round one (3-19 November) and round two.

Researchers compared the findings to the community infection survey and said that there was no statistical difference between school staff testing positive for covid-19 antibodies and the wider working age population in the same local authorities. Experts have said, however, that this does not mean transmission was not occurring in schools.

Julian Tang, clinical virologist at the University of Leicester, said, “The fact that these are not higher than the background community rate of transmission does not mean that it is not happening in schools (it is always hard to tell exactly where anyone caught the virus)—rather that the transmission rates in and out of schools in the community and homes have all reached an equilibrium. This is quite normal in compartments where movement of infected hosts and viruses is free and unimpeded between these compartments.”

The researchers also advised caution when interpreting the results due to the “small sample sizes and low response rates in pupils, introducing the possibility of selection bias.”

School measures

The survey also looked at what infection control measures had been adopted by schools. Questionnaires filled out by 105 schools relating to the autumn term 2020 found that almost all primary schools (38) had implemented all 10 of the measures strongly recommended by the Department for Education, and 91% of secondary schools reported implementing at least 12 of 15 strongly recommended measures.

Sinead Langan, the study’s co-chief investigator and professor of clinical epidemiology at the London School of Hygiene and Tropical Medicine, said, “Schools and staff have made really huge efforts to protect themselves and their students by implementing control measures to stop infection entering school sites and also to prevent onward transmission . . . There are some suggestions from the data that control measures may be working, if partially, to mitigate onsite infection, but more investigation would be needed to measure the tangible effects of these implementations.”

As schools in England are set to reopen from 8 March, the government has announced that households with school or college aged children, including child care and support bubbles, will be given access to two lateral flow covid-19 tests per week per person. The tests, which have caused much debate,2 will be available to order and collect from local sites.

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