Today Cochrane publishes an updated special collection of systematic and rapid reviews focused on a range of public health measures to control and prevent the spread of COVID-19. Many countries have adopted combinations of these measures and are faced with the challenge of easing or strengthening each of these measures over the course of the pandemic.
Coronavirus disease 2019 (COVID-19) is caused by a new virus, SARS-CoV-2, that has spread quickly throughout the world. As there is currently no effective treatment or vaccine for COVID-19 other ways of slowing its spread are needed.
What’s new in the Cochrane’s special collection?
Added to the special collection are three rapid reviews of the evidence on measures that aim to prevent potentially infected people from transmitting the virus to healthy people:
- Quarantine, where healthy people are separated from other healthy people in case they might have the virus because they either have had contact with a case or have travelled from an area with high transmission rates
- Travel-related control measures, such as border closures, partial travel restrictions and entry/exist screening
- Universal screening of people not seeking care for symptoms, either the general population or a targeted population based on their occupation, for example healthcare workers in hospitals and nursing homes.
What do the rapid reviews tell us?
- Quarantine is important in reducing incidence and mortality during the COVID-19 pandemic
- Travel control measures during the COVID-19 pandemic may have a positive impact on infectious disease outcomes
- One-time screening of healthy people looking for symptoms, temperature, international travel history, exposure to known or suspected infected people, or symptoms plus body temperature is likely to miss people who are infected.
What are the limitations of the evidence?
COVID-19 research is rapidly evolving, but the evidence base is still very uncertain. Evidence about the economic and social harms resulting from these measures is lacking. Much of the evidence currently available to help policy makers with public health decisions is based on mathematical modelling, which relies on making assumptions with imperfect data. Some 'real-life' evidence from observational studies is now available, however the certainty of the evidence from this type of study design is generally low or very low because the studies are often poorly designed or conducted.
What are the challenges for decision making?
To maintain the best possible balance of public health measures, decision makers must constantly monitor their outbreak situation and assess the impact of the measures implemented. Future research will help to disentangle the effects of these diverse prevention and control measures and will help determine which measures or combinations of measures may work best while minimising the harms to our communities.
More about the rapid reviews
- Low-certainty evidence from mathematical modelling studies consistently indicates that quarantine is important in reducing the number of people with COVID-19, but the size of the reduction is uncertain.
- Estimates range from a minimum reduction in the number of people with the disease of 44%, and a maximum reduction of 96%.
The lead author Barbara Nussbaumer-Streit (Danube University Krems, Austria) said: “We published the first version of this review in April 2020. Since then 22 additional studies on quarantine for COVID-19 have become available. While the number of studies has increased significantly in a short space of time, the evidence base is still limited because most studies on COVID-19 are mathematical modelling studies that make different assumptions on important model parameters. The evidence suggests that implementation of quarantine early on in a pandemic and combining quarantine with other public health measures such as physical distancing, can help slow the spread of COVID-19. However, it is difficult to determine what combination of measures is the best to reduce the number of cases and deaths.”
- Very low-certainty evidence from modelling studies suggests that when implemented at the beginning of an outbreak, cross-border travel restrictions may lead to a reduction in the number of new cases of between 26% to 90%.
- Observational studies of entry and exit screening evaluated different combinations of symptom-based screening, single (and rarely repeated) PCR swab testing and observation during quarantine.
- Very low-certainty evidence suggests that the proportion of cases detected at the border ranged from 0% to 75%.
- Entry and exit symptom screening measures on their own are not likely to be effective in detecting enough cases to prevent new cases becoming established within the protected region.
- A combination of approaches including symptom screening, quarantine, observation and PCR testing may help to more accurately identify positive cases.
Lead author Jacob Burns (Ludwig-Maximilians-University, Munich, Germany) said: “Travel-related control measures are not implemented in a vacuum, and their impact will be influenced by other factors, like the stage of the pandemic, whether community transmission has been established, whether other measures like physical distancing and wearing of facemasks have been implemented. The studies included in our review rarely investigated these aspects.”
- This review highlights the uncertainty and variation in accuracy of screening strategies.
- Observational studies evaluated different screening strategies, mainly screening people once rather than repeatedly, and involved either asking about symptoms, international travel, or exposure to a known or suspected case, performing temperature checks, or a rapid point-of-care test.
- Some studies combined screening for symptoms and temperature checks. With any screening strategy a high proportion of infected individuals may be falsely identified as negative.
- Future population-based screening studies will add substantially to our understanding of the effectiveness and accuracy of screening for COVID-19.
Lead author Meera Viswanathan (RTI International, North Carolina, USA) said: “We are unsure whether combined screenings, repeated symptom assessment, or rapid laboratory tests are useful. Because screening can miss people who are infected, public health measures such as face coverings, physical distancing, and quarantine for those who may have contact with an infected person, continue to be very important.”
Visit the full Cochrane Special Collection of systematic and rapid reviews focused on a range of public health measures to control and prevent the spread of COVID-19: Coronavirus (COVID-19): infection control and prevention measures