What is the evidence for social distancing during global pandemics? – a lay summary
In response to the COVID-19 pandemic, the UK government has mandated “social distancing” measures, such as restricting when people can leave their homes, and closing schools and public spaces, to reduce transmission of the virus. Are the measures likely to be enough? Or too much?
Real-time decision making needs to be based on the best possible evidence. But the body of knowledge around COVID-19, although growing all the time, is still limited. In the meantime policy decisions have to be made, and where there are information gaps we need to take into account experience from other similar scenarios, such as past influenza pandemics.
The best available evidence from previous pandemics supports social distancing measures as being effective at reducing and delaying the spread of infection, although the benefits may come at a heavy social cost.
- Self-isolation and other measures that keep infected people from making physical contact with others has been found to reduce the rate of infection spread and may also delay the pandemic’s peak – buying valuable time for health services to get ready.
- Home quarantine for people who have been exposed to the disease but who do not show symptoms, can also help slow the spread of infection. But there could be risk to others in the same household, especially if the quarantine lasts for a long time.
- Contact tracing, particularly when combined with other social distancing measures, may delay the peak of a pandemic. However it is resource-intensive, so may need to be limited to cases where it will bring the greatest benefit.
- School closures have helped reduce spread during influenza pandemics, although there is no agreement over when and for how long to close – there is some evidence that infections may bounce back again after school reopens. Prolonged school closures can also be counter-productive if infected children simply carry the disease to other social groups; they also handicap workforces and can result in loss of income for parents. There is a danger that some children might be poorly cared for, or themselves be left in charge of younger siblings.
- Changes in the workplace, such as remote working, staggered shifts, and extended holidays, have also been shown to help slow spread and delay peak infection. But the gains must be balanced against loss of income from work closures, and interruptions to supply chains for essential and important goods.
- Avoiding crowds and mass gatherings, and travel restrictions – the evidence is less strong for these but they may be beneficial if combined with other interventions.
Evidence specific to the current COVID-19 pandemic is limited but some trends are emerging. No one measure is likely to make much difference on its own – interventions need to be combined. Modelling studies suggest that self-isolation of people suspected of having COVID-19, coupled with home quarantine for those living in the same household, and social distancing of elderly people and others at most risk of severe disease might halve the number of deaths and reduce peak healthcare demand by two-thirds and deaths by a half. The greatest benefits seem to come from step-by-step introduction of social distancing measures, beginning in the areas with the highest prevalence. Getting the timing right is crucial.
Mandy Payne, 1 April 2020
This is a lay summary of a report repared for the Oxford COVID-19 Evidence Service of the Oxford Centre for Evidence Based Medicine, Nuffield Department of Primary Care Health Sciences, University of Oxford by Kamal R Mahtani, Carl Heneghan, and Jeffrey K Aronson, and posted on 20th March 2020.
Disclaimer: the article has not been peer-reviewed; it should not replace individual clinical judgement and the sources cited in the original report should be checked. The views expressed in this commentary represent an interpretation by HealthWatch and do not necessarily represent those of Oxford CEBM, the NHS, the NIHR, or the Department of Health and Social Care. The views are not a substitute for professional medical advice.