Largest Review Finds Good Evidence for Masks, Distancing in
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Non-pharmaceutical interventions, such as physical distancing of more than about 3 feet and wearing a medical mask and eye goggles, may be associated with reductions in COVID-19 transmission, a systematic review and meta-analysis found.

A review of at least 172 studies on SARS, MERS, and SARS-CoV-2, the virus that causes COVID-19, found transmission of viruses was lower with physical distancing of more than about 3 feet versus less than about 3 feet.

A subanalysis found that N95 respirators were 96% effective, considerably more so than other mask types (77% effective). For healthcare workers on COVID-19 wards, a respirator should be the minimum standard of care. This study should prompt a review of all guidelines that recommend a medical mask for health workers caring for COVID-19 patients," the researchers wrote.

Researchers examined 172 observational studies across 16 countries and six continents, as well as 44 relevant comparative studies in healthcare and non-healthcare settings, for a total of around 26,000 patients. They used the GRADE approach to rate the certainty of evidence.

Overall, 29 unadjusted studies and nine adjusted studies found "a strong association" between proximity and risk of infection, including six studies on COVID-19, with "moderate certainty."

For face mask versus no face mask, 29 unadjusted studies and 10 adjusted studies on face masks versus no face masks found a "large reduction in risk of infection," albeit with "low certainty." Eye protection, such as face shield and goggles, was associated with reduced risk versus no eye protection in 13 unadjusted studies, but with "low certainty."

Government and the public health community can use these results to provide advice for both community settings and healthcare workers about how to reduce risk.

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