Rapid Review: Quarantine alone or in combination with other public health measures to control COVID‐19

Background

Coronavirus (COVID‐19) is a new virus that has spread quickly throughout the world. COVID‐19 spreads easily between people who are in close contact, or through coughs and sneezes. Most infected people suffer mild, flu‐like symptoms but some become seriously ill and even die.

There is no effective treatment or vaccine (a medicine that stops people catching a specific disease) for COVID‐19, so other ways of slowing (controlling) its spread are needed. One of the World Health Organization’s (WHO) recommendations for controlling the disease is quarantine. This means separating healthy people from other healthy people, in case they have the virus and could spread it. Other similar recommendations include isolation (like quarantine, but for people with COVID‐19 symptoms) and social distancing (where people without symptoms keep a distance from each other physically).

What did we want to find out?

We wanted to find out whether and how effectively quarantine stops COVID‐19 spreading and if it prevents death. We wanted to know if it was more effective when combined with other measures, such as closing schools. We also wanted to know what it costs.

Study characteristics

COVID‐19 is spreading rapidly, so we needed to answer this question as quickly as possible. This meant we shortened some steps of the normal Cochrane Review process. Nevertheless, we are confident that these changes do not affect our overall conclusions.

We looked for studies that assessed the effect of any type of quarantine, anywhere, on the spread and severity of COVID‐19. We also looked for studies that assessed quarantine alongside other measures, such as isolation, social distancing, school closures and hand hygiene. COVID‐19 is a new disease, so, to find as much evidence as possible, we also looked for studies on similar viruses, such as SARS (severe acute respiratory syndrome) and MERS (Middle East respiratory syndrome).

Studies measured the number of COVID‐19, SARS or MERS cases, how many people were infected, how quickly the virus spread, how many people died, and the costs of quarantine.

Key results

We included 29 studies. Ten studies focused on COVID‐19, 15 on SARS, two on SARS plus other viruses, and two on MERS. Most of the studies combined existing data to create a model (a simulation) for predicting how events might occur over time, for people in different situations (called modelling studies). The COVID‐19 studies simulated outbreaks in China, UK, South Korea, and on the cruise ship Diamond Princess. Four studies looked back on the effect of quarantine on 178,122 people involved in SARS and MERS outbreaks (called ‘cohort’ studies). The remaining studies modelled SARS and MERS outbreaks.

The modelling studies all found that simulated quarantine measures reduce the number of people with the disease by 44% to 81%, and the number of deaths by 31% to 63%. Combining quarantine with other measures, such as closing schools or social distancing, is more effective at reducing the spread of COVID‐19 than quarantine alone. The SARS and MERS studies agreed with the studies on COVID‐19.

Two SARS modelling studies assessed costs. They found that the costs were lower when quarantine measures started earlier.

We cannot be completely certain about the evidence we found for several reasons. The COVID‐19 studies based their models on limited data and made different assumptions about the virus (e.g. how quickly it would spread). The other studies investigated SARS and MERS so we could not assume the results would be the same for COVID‐19.

Conclusion

Despite limited evidence, all the studies found quarantine to be important in reducing the number of people infected and the number of deaths. Results showed that quarantine was most effective, and cost less, when it was started earlier. Combining quarantine with other prevention and control measures had a greater effect than quarantine alone.

This review includes evidence published up to 12 March 2020.

The Cochrane Editorial and Methods Department (EMD) Editorial Service managed the editorial process for this rapid review in collaboration with the Cochrane Infectious Diseases Group (CIDG). The CIDG editorial base is funded by UK aid from the UK government for the benefit of low- and middle-income countries (project number 300342-104). The views expressed do not necessarily reflect the UK government’s official policies.