Evidence on mass wearing of masks weak, say experts

The issue of whether members of the public should wear face masks is difficult, due to weak evidence, the Government’s leading experts have said.

Deputy chief medical officer Dr Jenny Harries said while there is “probably a very, very small potential beneficial effect” in some enclosed environments, “the evidence is really very, very difficult to tease out”.

Meanwhile Professor Peter Horby, chairman of the New and Emerging Respiratory Virus Threats Advisory Group (NERVTAG), which is looking into the benefits of face masks, called the data “weak”.

His words were echoed by chief scientific adviser Sir Patrick Vallance at Thursday’s Downing Street press conference, who said the evidence on face masks “has always been quite variable, quite weak and difficult to know”.

However, Government scientific advisers have now finalised their advice on the wearing of face masks by the public, Downing Street confirmed.

The Prime Minister’s official spokesman said the Cabinet was told on Thursday that the recommendations of the Scientific Advisory Group for Emergencies (Sage) had been submitted for ministers to consider.

“They have finalised their advice. Ministers will now be reviewing this to decide on any further action that might be needed,” the spokesman said.

Scientific advisers for the Government had been carrying out a review of the use of face masks, despite the World Health Organisation (WHO) saying that there is no evidence to support their use by the general population.

Dr Harries said “the fact that there is a lot of debate means that the evidence either isn’t clear or is weak”.

“The number one thing is, we must leave our medical masks, if you like, for those people that need them at the front line, because there is clear evidence that that is beneficial.

“For the average member of the public, and it may be for example if you’re walking out in an open space, you’re practising good social distancing measures, you are neither going to be a risk to anybody else or to yourself.

“So it’s not quite so simple as just wearing a mask or not,” she told ITV’s Good Morning Britain.

Asked about places where it is difficult to effectively social distance, such as on tube trains, Dr Harries said: “So taking aside the risk that you might actually be creating a problem, in a sense of trapping the virus and then not disposing of it carefully, there is probably a very, very small potential beneficial effect in some enclosed environments.

“But the evidence is really very, very difficult to tease out.”

Meanwhile, Prof Horby said he does not personally wear a mask when he goes outside.

“The data are difficult and the reason that you’re seeing different policies is because the data are weak,” he told BBC Radio 4’s The World At One programme.

Prof Horby said that if you look at the testing of masks in “field conditions”, where they are given to people in the community, “their effectiveness is much, much lower”.

He added: “There’s also the problem of wearing the mask properly, they’re very difficult to wear properly for a long time, and so for prolonged exposures their effectiveness is really quite low.”

On Wednesday, Chris Hopson, chief executive of NHS Providers, urged the Government to “fully assess” the impact any new advice could have on health service supplies.

While in the Commons, Health Secretary Matt Hancock said: “We’ll follow the advice, we’ll listen to what the Sage advisory group says on masks and then we will implement that.”

He added that if the advice was changed, the Government “can’t promise that we will give everybody free masks”.