with the changing advice.
Many health authorities, previously discouraged the public from wearing masks to avoid COVID-19.
However, emerging evidence has caused,
...to reconsider whether the public should wear masks.
There are of course different types of face masks, and we are mainly considering disposable surgical masks.
Do these face masks work?
Experiments with mock viruses and patients in laboratories suggest surgical masks should help prevent viral illnesses "if used correctly".
Yet, randomized trials done on people in their homes or communities often show little, if any, benefit. A problem is that many of these studies did not fairly test how protective masks were.
In most trials, many people who were supposed to wear the masks didn't wear them as instructed - and some who were never supposed to wear masks, did wear them.
This means the evidence is messy...
What these studies mainly show is that it was difficult to get people to use masks as instructed even when participating in a clinical trial.
Other forms of evidence from studies in community settings do suggest that mask-wearers had somewhat fewer respiratory infections than those who didn't wear masks.
However, even taking these many different variables into account, our review found evidence that masks can be most protective for those at higher risk of infection when worn for short periods of time.
Should everyone wear masks?
So far, the official answer in the UK, for example, has been no.
This puts healthcare workers at risk of getting COVID-19.
But emerging evidence is changing the balance of potential harms and benefits. We know that people are infectious very early after becoming unwell.
Other evidence shows wearing masks does reduce the risk of infected people spreading the infection to others. With this evidence, arguments against everyone wearing masks in public are looking less certain.
Countries that previously recommended against wearing face masks in public (including the US) are changing their minds.
have even started recommending
people wear cloth masks.
Danilova Janna/ Shutterstock
But with the current shortage of masks, we have to think carefully about who would benefit most from wearing them.
Recent deaths in doctors and nurses remind us of the need to give these people priority.
Based on current evidence,
Are there any other problems with wearing masks?
Mask wearing can have its own problems.
Surgical masks are uncomfortable, can be difficult to wear for long periods, costly, and contribute to landfill waste.