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Face masks slash infection rates – but don’t give up on distancing: Study
Researchers say this demonstrates transmission of the virus is dominantly via airborne spread, but some experts disagree.
The researchers say the practices of handwashing and social distancing should continue, but that such measures alone are ‘insufficient’ in protecting against COVID-19.
For some time now, Australians have been advised to socially distance and employ frequent handwashing as measures to help prevent spread of COVID-19.
Meanwhile, questions remained on the usefulness of face masks.
That may have partly related to their limited availability at a time when their use needed to be prioritised for health professionals on the frontline.
However, the tide may now be turning in favour of their use.
On 5 June, the World Health Organization (WHO) changed its recommendation to now advise the general public to wear face masks when social distancing is not possible, such as on a crowded bus, train or plane.
That recommendation followed the 1 June publication of a systematic review and meta-analysis in The Lancet that reported face mask use ‘could result in a large reduction in risk of infection’ with COVID-19.
And new research published in the journal Proceedings of the National Academy of Sciences (PNAS) suggests wearing a face mask dramatically reduces a person’s chances of infection with COVID-19.
Furthermore, study author Professor Renyi Zhang says it may form a key part in offering the best protection against the virus.
‘By analysing the pandemic trends without face-covering, using the statistical method and by projecting the trend, we calculated that over 66,000 infections were prevented by using a face mask in little over a month in New York City,’ he said.
‘We conclude that wearing a face mask in public corresponds to the most effective means to prevent inter-human transmission.
‘This inexpensive practice, in conjunction with social distancing and other procedures, is the most likely opportunity to stop the COVID-19 pandemic.’
The authors say their results show ‘that the airborne transmission route is highly virulent and dominant for the spread of COVID-19’.
‘Our work suggests that the failure in containing the propagation of COVID-19 pandemic worldwide is largely attributed to the unrecognised importance of airborne virus transmission,’ they wrote.
‘Other mitigation measures, such as social distancing implemented in the United States, are insufficient by themselves in protecting the public.’
For the new research, the authors analysed trend and mitigation measures in three epicentres –Wuhan, China, Italy, and New York City, from 23 January to 9 May.
Researchers were keen to note, however, that using a face mask should not replace other recognised measures to help protect against spread of COVID-19.
‘Social distancing and washing our hands must continue, but that’s not sufficient-enough protection,’ they wrote.
Some of the conclusions from this new study make sense to Associate Professor Hassan Vally, an epidemiologist with a special interest in infectious diseases at La Trobe University.
He told newsGP the bulk of the researchers’ conclusions about face masks are consistent with recent messages.
‘What they’re really saying is that the evidence is out there now that [face masks] are highly protective and I don’t think anyone is disputing that, even though it took a little while for the World Health Organization to come on board with the latest evidence,’ he said.
But Associate Hassan Vally disagrees with the idea that the fact face masks have been shown to reduce transmission proves airborne spread is the dominant COVID-19 transmission route.
‘We don’t have a lot of evidence to support this idea and there are a lot of uncertainties, so we need to be cautious about this conclusion that has been drawn by the authors,’ Associate Professor Vally said.
The study is also drawing criticism elsewhere in the medical community, with infectious diseases epidemiologist and scientist Kate Grabowski from Johns Hopkins University tweeting that three faculty members and one PhD trainee rapidly reviewed the article.
‘All agree that PNAS should consider a retraction,’ she tweeted.
‘There are so many limitations, it’s hard to know where to begin. Perhaps the most critical being that none of the stay at home orders or other contact reduction interventions had any impact on transmission.’
Considering Australia’s relatively low number of detected COVID-19 cases, some may say that advice regarding the use of face masks is not relevant here.
Associate Professor Vally, however, believes it is.
‘On average, because of all the great work that we’ve done, the risk [of catching COVID-19] is pretty low, which is great news,’ he said. ‘But I would say there’s quite a high probability that there are people with COVID out there in the community that we don’t know have it, so we certainly haven’t eliminated it.
‘And if we haven’t eliminated it, there’s also a risk of a resurgence and a risk of a particular cluster occurring, and the consequences could be quite considerable for certain people.’
He said a balance is therefore needed between ‘not overreacting’ and understanding the risks associated with a rise in detected cases.
‘There is a potential of a second wave and it only takes something like the demonstrations that have occurred and that could set us back weeks or months,’ he said.
Associate Professor Vally said patients seeking advice from their GP on whether or not to wear a face mask in crowded public places need to understand the difference between population-level advice and individual risk.
‘If you look at averages across the whole population, we clearly don’t have a lot of COVID circulating right now, and so that’s probably why the Government is kind of holding back and not making it a requirement on public transport,’ he said.
‘However, that’s totally different to a decision an individual might make.’
Consequently, Associate Professor Vally believes advice to patients needs to be given on a case-by-case basis, taking into account a patient’s health and whether they are able to effectively socially distance when out of the house.
‘It’s not this easy black-and-white sort of answer,’ he said.
But if he had heart disease or a similar comorbidity and was unable to socially distance in a crowded space, Associate Professor Vally would certainly wear a face mask.
‘Because why wouldn’t you?’ he said.
‘It doesn’t cost very much, and we know it adds an extra level of protection.’
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