Schools do not need to close to reduce COVID-19 but other measures are advisable.

About 1.3 billion students worldwide were affected by school or university closures in April 2020 due to the COVID‐19 pandemic. However, closing schools is controversial. Does it really protect school children, their teachers and families? Or could mitigation measures be as effective as school closures? According to data from the European Centre for Disease Prevention and Control, children and adolescents aged 1–18 years accounted for 0.13% of the COVID‐19 deaths in Europe from 1 August to 29 November 2020.  Therefore, the main aim of disease control in schools is to protect the staff and parents. Two extensive studies have addressed these questions about school closures and mitigation measures.

The first was a registered study of the Swedish population. Led by economist Jonas Vlachos, it used three national registers to study the occurrence of COVID‐19 in different groups in Sweden during spring 2020. That was when the country closed upper secondary schools for children aged 17–19 years in grades 10–12, but kept lower secondary schools for children aged 14–16 in grades 7–9 open. All countries within the European Union and the European Economic Area, except Iceland and Sweden, closed primary schools during part of the pandemic and all closed secondary schools at some point.

This means that school closures in Sweden could be evaluated by comparing grade 9 children in the open schools and grade 10 children in the closed schools. The comparison showed a small increase in infections amongst the parents of the younger children in the open schools, and double the infection rate in their teachers when they were compared to the teachers of the older children, who were receiving online teaching instead. These infections were spilled over to the teachers' partners.

Keeping the lower secondary schools open had an impact on the spread of the virus that causes COVID‐19. Vlachos et al compared 124 occupations, excluding health professionals, and upper secondary teachers were at the median level, whilst lower secondary teachers were the seventh‐most affected occupation. However, they were much less affected than people like taxi drivers, police officers and social workers. Up to June 2020, closing all lower secondary schools in Sweden could have saved the lives of five parents and 1.5 teachers and their partners, according to highly uncertain calculations. A large portion of the virus transmissions to teachers was probably from other school staff, not from students. Measures to protect them could be considered. The authors did not recommend closing lower secondary schools. Unfortunately, wearing face masks is not common in Sweden, but mandatory face masks for teachers could be considered.

The second study was a massive online survey carried out in the United States. Epidemiologist Justin Lessler and his team used data from the ongoing Facebook‐based COVID‐19 Symptom Survey, which is administered by Carnegie Mellon University. It yields approximately 500,000 survey responses a week from the 50 US states and the US capital Washington DC. The researchers found that living in a family with a child attending full‐time, face‐to‐face schooling was associated with a significant increase in the odds of reporting a COVID‐19‐like illness (adjusted odds ratio 1.38, 95% confidence ratio 1.30–1.47). Lessler et al agreed with Vlachos et al that the strength of the associations increased as the children got older. Transmission of COVID‐19‐like illnesses in children attending open schools part‐time, compared to full‐time, was attenuated but still statistically significant. Teachers working in open schools were more likely to report a COVID‐19‐like illness than those working at home. The elevated risk was of the same magnitude as health care and office workers.

Lessler et al studied 14 school‐based, low‐cost mitigation measures, including three associated with significant reductions in risk: daily symptom screening, mandatory masks for teachers and cancelling extra‐curricular activities. When seven or more mitigation measures were in place there was no significant difference in the occurrence of a COVID‐19‐like illness between children attending school full‐time or studying at home because their school was closed.

The findings of these two research groups in Sweden and the USA are supported by other studies. , In spring 2020, Swedish preschool teachers and school teachers had relative risks of 1.10 and 0.43, respectively, of needing intensive care due to COVID‐19. This was when they were compared with other occupations, excluding healthcare workers.  The European Centre for Disease Prevention and Control performed a comprehensive search of the relevant literature up to 18 November 2020.  The review concluded that adults were not at higher risk of the virus that causes COVID‐19 in school setting than in other settings. Precautionary physical distancing measures should be used when staff interact with adolescents and other adults. It is important to remember that school closures can have detrimental effects on children and society. The children's rights to education are at risk and untold numbers of healthcare workers and other workers have to stay at home to look after their children, which exacerbates staff shortages and economic hardship for families. Children also miss out on school lunches and school health care. , In some cases, closing schools may cause more harm than benefits for children.

Until they are vaccinated, teachers and other school staff should use masks, at least when they meet other adults and upper secondary students indoors. In autumn 2021, when our experiences of vaccinating teenagers have accumulated in Canada, the USA and other countries, it will be possible to make informed recommendations on vaccinations for those aged 12–17.

However, by mid‐May 2021, only 0.3% of the global vaccine supply was going to low‐income countries, according to the World Health Organization. Sometimes there were not even enough supplies to vaccinate healthcare workers.  The Director‐General stated that instead of vaccinating lower risk groups, like children and adolescents, rich countries should consider donating vaccine supplies to poorer countries. Vaccinations will probably decrease the disease burden in poorer countries and decrease the worldwide spread of new mutations of the virus, which is a win‐win situation.

The studies published so far have not discussed the importance of the new virus mutations discovered in the UK, Brazil, South Africa and India. A search of the PubMed and Cochrane databases in May 2021 did not reveal any studies of these mutations in school settings. Some of them are transmitted faster than the original virus, but so far we have no proof of whether they cause more or less deaths.

In conclusion, daily symptom screening, mandatory masks for teachers and cancelling extra‐curricular activities at school protects parents and school staff from COVID‐19. Closing primary and lower secondary schools should be avoided. There is no need to prioritise teachers during mass vaccinations against COVID‐19, but the impact of new mutations is so far unknown. The World Health Organization has urged rich countries to donate vaccines to poorer countries, rather than vaccinate low‐risk groups like children and adolescents.

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