Donning a face mask more than halves the risk of getting Covid, according to a review of eight studies published in the British Medical Journal. So does hand-washing. Physical distancing, meantime, cuts the risk by a quarter.
The findings come amid evidence that vaccination efforts weren't enough to prevent a resurgence as temperatures drop and people crowd indoors, forcing countries including Austria and the Netherlands to introduce curbs.
"It is likely that further control of the Covid-19 pandemic depends not only on high vaccination coverage and its effectiveness but also on ongoing adherence to effective and sustainable public-health measures," authors including Stella Talic, the study's lead researcher and an epidemiologist at Monash University in Melbourne, said in the paper.
The scientists struggled to evaluate the public-health measures and said they couldn't assess other efforts such as quarantines, lockdowns and school closures because studies were too disparate. They called for more research, saying their findings were limited by a lack of reliable and comparable data.
An accompanying editorial in the BMJ said funding on public-health measures accounts for just 4% of global Covid research.
"Considering the central importance of public health and social measures for pandemic control, the uncertainties and controversies around their effects, and the immense research effort being put into vaccine and drug development, this lack of investment in public health measures is puzzling," Paul Glasziou, the director of the Institute for Evidence-Based Healthcare at Australia's Bond University, wrote in the editorial with scientists from the U.K. and Norway.
Glasziou and his colleagues also sought to explain the researchers' hand-washing finding -- a surprising conclusion considering coronavirus transmission in mostly airborne. The results may reflect how people who wash hands frequently tend to take other steps as well.
"It is likely that hand-washing is a marker for several protective behaviors such as avoiding crowds, distancing, and mask wearing," they said.