Quarantine alone or in combination with other public health measures to control COVID‐19: a rapid review

Cochrane published a rapid review in September 2020 where the effects of quarantine (alone or in combination with other measures) of individuals who had contact with confirmed or suspected cases of COVID‐19, who travelled from countries with a declared outbreak, or who live in regions with high disease transmission were assessed.

The evidence current up to 23 June 2020 included 51 studies. Thirty‐two studies focused on COVID‐19, 14 on SARS, three on SARS plus other viruses, and two on MERS. Most studies combined existing data from multiple sources and assumptions to create a model (a simulation) for predicting how events might occur over time, for people in different situations (called modelling studies). Four COVID‐19 studies observed the effects of quarantine (observational studies) on 6064 individuals in China, Greece and Singapore. Twenty‐eight COVID‐19 studies simulated outbreaks in Algeria, China, Canada, Italy, Kazakhstan, Nepal, UK, USA, Singapore, South Korea, on the cruise ship Diamond Princess, and in a general population. Four studies looked back on the effect of quarantine on 178,122 people involved in SARS and MERS outbreaks. The remaining 15 studies modelled SARS and MERS outbreaks.

The modelling studies all found that simulated quarantine measures reduce the number of people with COVID‐19 and the number of deaths. With quarantine, estimates showed a minimum reduction in the number of people with COVID‐19 of 44%, and a maximum reduction of 96%. Similarly, with quarantine, estimates of the number of deaths showed a minimum reduction of 31%, and a maximum reduction of 76%. Combining quarantine with other measures, such as closing schools or physical distancing, may be 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 may be lower when quarantine measures start earlier. The authors are uncertain about the evidence they found for several reasons. The observational studies on COVID‐19 did not include a comparison group without quarantine. 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 they only provide indirect evidence. Despite limited evidence, all the studies found quarantine to be important in reducing the number of people infected and the number of deaths. Results suggest that quarantine was most effective, and cost less, when it started earlier. Combining quarantine with other prevention and control measures may have a greater effect than quarantine alone.

The review can be accessed at https://www.cochranelibrary.com/cdsr/doi/10.1002/14651858.CD013574.pub2/full#CD013574-abs-0002