Coronavirus: How effective are face masks at stopping spread?
In August, it became compulsory to wear a face mask in museums, galleries, cinemas and places of worship in England.
It was already compulsory to wear a face covering when visiting a supermarket, indoor shopping centre, coffee shop, or bank in England, with those who fail to comply at risk of being fined up to £100.
When secondary schools in England reopened in September, schools in areas of local lockdown were also required to make students and staff wear masks in communal areas or places where social distancing was difficult to adhere to.
Schools in other areas are not mandated to wear them but can decide to do so on an individual basis.
Initially legislation only required face coverings be worn on public transport (from 15 June) but that has now expanded to many other public areas.
This follows months of ministers saying face coverings were not-essential, despite the easing of lockdown and other countries introducing requirements to do so.
On Sunday 12 July, senior Conservative minister Michael Gove was still saying people should rely on “common sense” and should not be forced to wear them by the government.
In July, scientists said that mask-wearing should be adhered to in all public places where it is hard to social distance, particularly in crowds.
So just how effective is mask wearing? Does it protect the wearer from contracting the virus or just prevent the wearer from spreading anything they might not know they have?
Can face masks protect me?
The UK government, the World Health Organisation (WHO) and the Center for Disease Control and Prevention (CDC) in the USA, have all shifted their position on wearing masks during the pandemic – these moving guidelines may have sowed confusion as to their benefit.
In February Public Health England were not encouraging the public to wear them; Dr Jake Dunning, head of emerging infections and zoonoses [infectious disease spread between humans and animals] at PHE, told The Independent that there is “very little evidence of a widespread benefit” in members of the public wearing masks.
Dr Dunning explained there are a number of reasons why they can be ineffective. “Face masks must be worn correctly, changed frequently, removed properly, disposed of safely and used in combination with good universal hygiene behaviour in order for them to be effective.”
At the time, experts were also keen to stress the need for people on the frontline to be wearing supplies of personal protective equipment (PPE), rather than the community.
But – since then – numerous studies have shown that wearing any type of face covering (not surgical grade, which should be left to medical staff) over the nose and mouth, can help in reducing spread of viral droplets when a person coughs or sneezes.
A report, published in Nature journal in April, said: “Face masks significantly reduced detection of influenza virus RNA in respiratory droplets and coronavirus RNA in aerosols, with a trend toward reduced detection of coronavirus RNA in respiratory droplets.”
Another study used high-speed video to track droplets and found even holding a washcloth over the mouth was effective in blocking the droplets (similarly a microbiologist shared photographs of bacteria culture spread with and without a mask).
An international report published in The Lancet on 3 June, which analysed data from 172 studies in 16 countries, found that by wearing a face mask there is just a 3% chance of catching COVID-19. And a study by Cambridge University, published on 10 June, says even basic homemade masks can reduce transmission – and could even help prevent a second wave.
A separate study, conducted by the University of Edinburgh, and published on 2 July also suggested that wearing a face covering could help reduce the spread of coronavirus from people who are carriers. The research showed that wearing a covering over the mouth and nose can reduce the forward distance travelled by an exhaled breath by more than 90 per cent.
On 8 July, Oxford University’s Leverhulme Centre for Demographic Science, published a study, with the message: “Cloth face coverings, even homemade masks made of the correct material, are effective in reducing the spread of COVID-19 – for the wearer and those around them” and warned “face masks and coverings work – act now”.
So is this mainly about stopping asymptomatic transmission?
Yes. The research largely suggests face masks won’t necessarily stop you catching Covid-19 but will lessen the chance of you passing it on if you are asymptomatically carrying and unaware of this (so not isolating at home).
On 8 April, the WHO published a report saying masks did not prevent healthy people from picking up coronavirus but did stop the virus spreading. It was based on a review of evidence from Hong Kong that suggested widespread use of face masks may have reduced the spread.
On 21 April the government’s DELVE ( Data Evaluation and Learning for Viral Epidemics group) in the Royal Society, said: “Face masks offer an important tool for managing community transmission of Covid19 within the general population.
“Our analysis suggests that their use could reduce onward transmission by asymptomatic and pre-symptomatic wearers if widely used, contrasting to the standard use of masks for the protection of wearers. If used widely and correctly, face masks, including homemade cloth masks, can reduce viral transmission.”
On the government website, it agrees: “The evidence suggests that face coverings can help us protect each other and reduce the spread of the disease if someone is suffering from coronavirus, but not showing symptoms.”
Jimmy Whitworth, professor of international public health at the London School of Hygiene and Tropical Medicine, told The Independent that the benefit is largely for others, not yourself: “They’re more beneficial if you have a virus and don’t want to pass it on than to prevent catching anything.” This corroborates the WHO findings.
Professor David Heymann, of the London School of Hygiene and Tropical Medicine, who chaired the WHO’s scientific and technical advisory group, agreed that unless people were working in healthcare settings, masks are “only for the protection of others, not for the protection of oneself” – which is why the government is now making them non-optional.
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