Research on how well various types of masks and face coverings protect against coronavirus has varied but experts and politicians have generally leaned towards the idea that the chance of some protection is better than none.
In the UK, face coverings were first made mandatory in for public transport in June and later for shops and other indoor spaces in July.
Here's what studies have shown so far about whether masks work:
FACE MASKS LOWER VIRUS R RATE (JANUARY 2021)
Researchers at Boston University in the US found wearing face masks is an effective way to stop the spread of the coronavirus.
The study, published in the journal Lancet Digital Health, found a 10 per cent rise in self-reported mask wearing is associated with a three-fold increase in the odds of keeping the R number – the number of others each person with coronavirus infects – below 1.
Co-author of the study Ben Rader, of Boston Children's Hospital and Boston University, said: 'An important finding of this research is that mask wearing is not a replacement for physical distancing.'
INFECTIOUS DROPLETS WILL STILL SLIP THROUGH (DECEMBER 2020)
Scientists at New Mexico State University in the US found wearing a cloth mask may not shield the user totally from coronavirus because infected droplets can slip through, but it would significantly reduce how many.
'Wearing a mask will offer substantial, but not complete, protection to a susceptible person,' said Dr Krishna Kota, an associate professor at the university who led the research.
The study found while all masks blocked at least 95 per cent of droplets from coughs and sneezes - there was still a risk of the disease being passed on.
A MASK 'WILL ALWAYS BE BETTER THAN NOTHING' (DECEMBER 2020)
Research by the University of Massachusetts Lowell and California Baptist University in the US found wearing a used three-layer surgical mask can reduce the number of small droplets that are released into the air by two thirds.
Co-author Dr Jinxiang Xi said: 'It is natural to think that wearing a mask, no matter new or old, should always be better than nothing.
