By Connor Boyd Health Reporter For Mailonline
Published: 11:59 BST, 9 September 2020 | Updated: 11:59 BST, 9 September 2020
The mass-use of face masks may be acting as a de facto 'vaccine' against coronavirus, scientists have claimed.
Masks, particularly surgical and cloth ones worn by the bulk of the population, are not perfect and allow some viral particles to slip through into wearer's airways.
Experts say repeatedly exposing people to small amounts of Covid-19 could help to train the body to recognise and fight it off, effectively immunising them.
The unproven theory was detailed by scientists from the University of California in an editorial in the New England Journal of Medicine.
It is unlikely the hypothesis will be proven beyond doubt because that would require exposing people with and without masks to the virus in clinical trials, which would be unethical.
But the theory may partly explain why fewer people are dying or falling critical ill with the coronavirus.
The scientists behind the commentary have stressed that people should not get complacent or purposefully put themselves in harm's way of Covid.