The first global study of its kind shows that mask-wearing is the single most effective public health measure at tackling Covid.
Vaccines save lives around the world. Most do not give 100% protection, most countries have not given everyone a vaccine, and it is not known if jabs will prevent future transmission of emerging coronaviruses.
This month, Covid cases exceeded 250 million. The highly transmissible Delta variant of the virus is still infecting 50 million people every 90 days.
A systematic review and meta analysis of non-pharmaceutical interventions has found that mask wearing, social distancing and hand washing are the most effective measures to curb cases.
The researchers wrote that a systematic review and meta analysis shows that several personal protective and social measures are associated with reductions in the incidence of Covid-19.
They said the results show the need to wear a mask and wash hands with soap and water.
Researchers at the University of Edinburgh and the University of Monash say that multi-faceted measures, such as borders being closed, need further analysis to assess their potential negative effects on populations.
Public health interventions are known to be beneficial in fighting respiratory infections like flu, and countries around the world have tried using them to curb the spread of Covid.
Until now, reviews have not been strong enough to allow experts to make conclusions about the effectiveness of such measures.
A significant reduction in the incidence of Covid with mask wearing and a reduction in the incidence of Covid without mask wearing was shown from more than 30 studies.
After adjusting for the small number of hand washing studies included, the reduction in Covid incidence was not statistically significant.
The researchers said that the differences in study design, outcome measures and quality made it difficult to analyze other measures.
Many countries adopted mask wearing at the start of the epidemic, but have since dropped some of their requirements.
The Dutch government decided to re-impose the mandatory wearing of face masks in order to slow the rise in infections.
The Czech Republic, Slovakia, and Poland have recently tightened rules on mask wearing. Hungary has resisted making mask wearing compulsory in closed spaces.
The legal requirement to wear a mask in England ended in July, except in healthcare settings and care homes. In Wales, they are required on public transport and in all public indoor areas. In Scotland, masks must be worn in public places when not seated. In Northern Ireland masks are required on public transport and in shops.
The World Health Organization's special envoy for Covid criticized Boris Johnson, the UK prime minister after he was photographed without a face covering during a hospital visit.
Dr David Nabarro told Sky News that he was not sitting on the fence about the pictures of Johnson walking maskless through the General, and that everyone should do everything they can to avoid getting the virus or inadvertently passing it.
We know that wearing a face mask reduces the risk, we know that maintaining physical distance reduces the risk, and we know that hygiene by coughing into your elbow reduces the risk. We should do it all and not rely on any one intervention.
