Monaz: Hello, I'm Monaz Mehta, editor in the Cochrane Editorial and Methods department. Coronavirus disease 2019, or COVID-19, has spread quickly throughout the world, and Cochrane is producing a series of rapid reviews of the evidence to help decision makers respond to the pandemic. In this podcast, lead author, Barbara Nussbaumer-Streit from Danube University Krems in Austria outlines the findings of our review of the effectiveness of quarantine, which was requested by the World Health Organization and published in early April 2020.

Barbara: Most people with COVID-19 will suffer only mild, flu-like symptoms; but some become seriously ill, and some die. Non-medical public health interventions are needed to help control the spread of the disease. One strategy is for people who are at high risk of having it, to remain in quarantine.

We did our review to see if this helps prevent the spread of the virus and save lives. We also wanted to know the costs of quarantine and whether it was more effective when combined with other measures, such as closing schools. Jumping to the conclusion, the limited evidence we’ve found suggests that quarantine is an important component for controlling the spread of severe coronavirus-diseases, such as COVID-19.

To get as quick an answer as possible, we needed to shorten some of the steps of the normal Cochrane Review process, but we still searched very widely for relevant studies. We included non-randomized studies of interventions and modeling studies on quarantine alone or in combination with other public health measures to control COVID-19, or for earlier coronavirus-diseases. These include severe acute respiratory syndrome, known as SARS, and Middle East respiratory syndrome, which shortens to MERS.

We found ten modeling studies on COVID-19 and four observational studies, as well as 15 modeling studies on SARS and MERS.

The modeling studies consistently reported a benefit of the simulated quarantine measures. For example, the models estimated that quarantine of people exposed to confirmed or suspected cases of COVID-19 prevented between 44% and 81% of the cases that would otherwise have happened and 31% to 63% of the deaths, when compared to no such measures. The range of values reflects the different scenarios in the models. In regard to costs, the earlier the quarantine measures are implemented, the greater the cost savings will be.

The modeling studies also suggested that when quarantine is combined with other prevention and control measures, such as school closures, travel restrictions and social distancing, there is an even greater effect on the reduction of new cases, transmissions and deaths.

However, our confidence in the evidence is very limited. This is mainly because the COVID-19 studies based their models on the limited data that have been available in the early weeks of the pandemic and made different assumptions about the virus. On the other hand, although the studies of SARS and MERS might be stronger, we cannot be sure that their results would be the same for COVID-19.

In summary, despite only having limited evidence, all the studies found quarantine to be essential for controlling the spread of severe coronavirus diseases. It was most effective, and cost less, when started earlier. Combining quarantine with other public health measures had the greatest effect in reducing spread, and cutting the number of cases and deaths. Looking to the coming months, in order to maintain the best possible balance of measures, decision makers must continue to constantly monitor the outbreak situation and the impact of the measures they implement.”

Monaz: If you would like to read the full review it is available free online. Just go to Cochrane Library dot com and search 'COVID-19 and quarantine'.