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COVID-19: we need randomised trials of school closures
  1. Atle Fretheim1,2,
  2. Martin Flatø3,
  3. Anneke Steens4,
  4. Signe Agnes Flottorp1,
  5. Christopher James Rose5,
  6. Kjetil Elias Telle5,
  7. Jonas Minet Kinge3,
  8. Per Everhard Schwarze4
  1. 1 Centre for Informed Health Choices, Norwegian Institute of Public Health, Oslo, Norway
  2. 2 Faculty of Health Sciences, Oslo Metropolitan University, Oslo, Norway
  3. 3 Centre for Fertility and Health, Norwegian Institute of Public Health, Oslo, Norway
  4. 4 Infection Control and Environmental Health, Norwegian Institute of Public Health, Oslo, Norway
  5. 5 Health Services Division, Norwegian Institute of Public Health, Oslo, Norway
  1. Correspondence to Atle Fretheim, Norwegian Institute of Public Health, PO Box 222 Skoyen, N-0213 Oslo, Norway; atle.fretheim{at}

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One of the most controversial and radical societal interventions to curb the COVID-19 epidemic is the closing of schools and nurseries. There seems to be broad agreement that the effect this will have on the spread of the virus is uncertain, and the negative implications are obvious. Economic costs are high when parents must stay at home to take care of their children and cannot work1 for children, and social isolation and the impact on learning are key concerns, especially if school closures are long-lasting.

Empirical evidence on the effect of school closures stems from observations during influenza epidemics.2 3 Systematic reviews have not identified any randomised trials, but observational data indicate that school closures reduce the spread of influenza.2 3 However, while children play an important role in transmitting influenza viruses, the available data seem to show that their role may be smaller in the transmission of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2): relatively few children have tested positive, and children are mildly affected compared to adults,4 5 which is likely to mean that they are also less infectious.6 The facts that there are few documented cases of children as sources of transmission and no reports of outbreaks among children in schools or nurseries support the inference that children play a smaller role in the spread of SARS-CoV-2 than influenza.

From a ‘better safe than sorry’ perspective, school closures make sense. This is probably why most governments decided to close their schools.7 Interestingly, neighbouring and largely similar countries in Scandinavia have opted for different approaches: while Denmark and Norway implemented school closures, Sweden did not.8 Finland chose a middle way, allowing the youngest children to go to school, while urging they stay home.9

The decisions on whether to close schools were probably difficult to make, given the lack of robust evidence. Deciding when to reopen schools and nurseries will be just as challenging. At the time of writing, no government in Europe has announced when they will reopen schools fully. The Norwegian Prime Minister Erna Solberg declared on March 24 that schools will remain closed at least until April 1310—many believed they will remain closed over the summer, if not longer.

Given that the pandemic is likely to last into 2021, the question of when to reopen schools will remain a contentious one. The public is probably just as ambivalent about closed schools as the authorities are, and there is—presumably—a demand for reliable information to inform a decision about reopening.

As for any question about benefits and harms of interventions, the standard approach is to conduct a randomised trial—if possible. In Norway, we could do this by randomising schools in Norway’s 356 municipalities. A study period of 1 month should be sufficient to detect important differences in incidence of cases with COVID-19, though this needs further assessment due to the constantly changing circumstances. Harmful effects, for example, psychological outcomes, school performance and parental income, are important outcomes to include.

A technical challenge is statistical power, since it may be politically or practically impossible to conduct a trial of adequate duration if COVID-19 incidence is low. It would therefore be helpful if several countries or states ran similar trials, ideally using compatible outcomes to facilitate evidence synthesis. To facilitate such collaboration, we publish our study protocol for a cluster-randomised trial of school reopening, with this article (online supplemental material 1).

Supplemental material

The results of this and similar trials would inform policymakers about when or whether to reopen schools under the current COVID-19 epidemic and would constitute an important part of the evidence base for decisions about school closures in future epidemics.

Whether a national experiment in Norway is feasible remains to be seen. A prerequisite is that there is sincere doubt among decision makers and experts alike that reopening schools is the right thing to do.

With a skyrocketing unemployment rate and a halted economy, questions have been raised about whether the current drastic measures are justified.11 The largest business association in Norway, the Confederation of Norwegian Enterprises, recently asked the government to reopen nurseries and allow people to get back to work.12 Doctors report that the number of children admitted to hospital under suspicion of abuse has plummeted, and they express a deep concern for children in distress, that teachers normally would have notified the child welfare services about.13

So far, the focus has mainly been on the need to minimise the direct negative impact of the pandemic, and many are willing to pay a high price to succeed in that, at least in terms of economic costs. A recent modelling exercise by French researchers demonstrated the potential that may lie in closing down schools: they found that in combination with one in four adults working from home, ‘8 weeks of school closure would be enough to delay the peak of almost 2 months with approximately 40% reduction of the incidence at the peak’.14 For most countries, this would likely translate into a substantial number of lives saved, and could balance out the downsides. Two key assumptions for the calculation were that children are 80% less susceptible to COVID-19 infection than adults are, and 50% less infectious. However, there are large uncertainties about these assumptions, since there are no reliable estimates. If children rarely infect others, school closures are clearly doing more harm than good.

In a situation where it is unclear what the best option is—what clinical researchers refer to as ‘equipoise’—running a trial is the ethically sound alternative.



  • Correction notice This article has been corrected since it first published. The affiliations of authors MF and JMK have been corrected.

  • Twitter Atle Fretheim @atlefretheim.

  • Contributors AF wrote the first draft of the article and the guarantor. MF, AS, SAF, CJR, KET, JMK and PES commented on the draft and approved the final version.

  • Funding The authors have not declared a specific grant for this research from any funding agency in the public, commercial or not-for-profit sectors.

  • Competing interests None declared.

  • Patient consent for publication Not required.

  • Provenance and peer review Not commissioned; internally peer reviewed.

  • Supplemental material This content has been supplied by the author(s). It has not been vetted by BMJ Publishing Group Limited (BMJ) and may not have been peer-reviewed. Any opinions or recommendations discussed are solely those of the author(s) and are not endorsed by BMJ. BMJ disclaims all liability and responsibility arising from any reliance placed on the content. Where the content includes any translated material, BMJ does not warrant the accuracy and reliability of the translations (including but not limited to local regulations, clinical guidelines, terminology, drug names and drug dosages), and is not responsible for any error and/or omissions arising from translation and adaptation or otherwise.

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