Face coverings are compulsory again across a number of different settings in England, including shops and public transport.
But how much is known about how effective they are at controlling the spread of coronavirus?
Research suggests face coverings offer more protection to others than the wearers, but there is also some suggestion they may give some protection to the wearer.
Studies indicate transmission is more likely to occur indoors where people are close together.
And covering the nose and mouth reduces the spread of droplets carrying the virus from coughs, sneezes and while speaking, experts say.
Some studies on the effectiveness of wearing face coverings suggest they have a significant impact on the spread of the virus, while some researchers say there is little impact.
The level of protection can vary depending on the type of mask worn, and how people wear them.
A review on the effectiveness of face coverings to reduce Covid transmission in community settings has been published by the UK Health Security Agency (UKHSA).
The review included 25 studies, two randomised controlled trials (RCTs) and 23 observational studies conducted up to September 14 this year.
It reports that the evidence from two RCTs and 23 observational studies predominantly suggests face coverings can reduce the spread of Covid in the community, through both source control and wearer protection, as well as universal masking.
Three studies set in schools and a summer camp, and 11 other observational association studies, revealed mixed results for the effectiveness of face coverings.
While eight studies suggested face coverings were associated with reduced Covid-19 transmission, six studies suggested no statistically significant effect.
A document dated January 2021, published by the Scientific Advisory Group for Emergencies (Sage), states that face coverings can be effective in reducing transmission in public and community settings.
It sets out that their effectiveness stems mostly from reducing the emission of virus-carrying particles when worn by an infected person – also known as source control.
But with varying results from studies, there is disagreement among scientists about the effectiveness of masks.
Paul Hunter, professor of medicine at the University of East Anglia, said: “The evidence on the effectiveness of face coverings is at best mixed. Whilst most but not all studies do suggest that face coverings reduce risk of transmission these studies vary widely in their estimates of the effect size.
“In general, lower quality observational studies suggest greater effectiveness compared to higher quality experimental study designs. But all study designs have serious weaknesses.”
Dr Julian Tang, honorary associate professor/clinical virologist, University of Leicester, has said some form of face covering is better than none, but that there are many elements that go into reducing risk.
Professor Robert Dingwall, a sociologist from Nottingham Trent University, said that the policy on masks helped politicians show they were “seen” to be doing something.
Asked about mask policy, he told talkRadio: “I think this has very much to do with the desire to be seen to be doing something – I mean, it’s very visible effect.
“But I mean, as I’ve said on numerous occasions since summer 2020, we’ve not conducted proper research to find out whether they actually work or not.
“And the accumulating evidence is that the effect of the face mask, the value of face masks, is nil to minimal.
“We have a body of work which has been put together – much of it flawed, much of it problematic in quality – but without showing any consistent strong signal that there is any benefit to the community in the general adoption of face masks.”