A group of Kiwi public health experts have repeated calls for "mass masking" amid the Covid-19 pandemic – this time setting out the benefits for people riding on buses or crossing the border.
The use of masks has been debated among researchers; while many have argued they offer extra protection, a recent Government-commissioned review found there wasn't enough scientific evidence to make recommendations either way.
Nonetheless, Otago University researchers have doubled down on earlier calls for mass masking in a blog post today.
Those experts – professors Nick Wilson and Michael Baker, and doctors Sophie Febery, Ling Chan and Amanda Kvalsvig – said there was "significant" indirect evidence from mask-wearing countries to indicate the practice was an effective public health measure when combined with hand-washing and physical distancing.
They described mass masking as a "low-cost intervention" with minimal risks and "significant" potential benefits.
At borders, airline and ship crew, currently exempt from quarantining requirements, could reduce the risk of bringing new cases into the country by wearing masks – particularly as rapid contact tracing was difficult amid people travelling.
It would give more confidence to international students and others flying between here in Australia in a future trans-Tasman bubble, they said, while also helping protect staff at the borders.
They said mass-making could also create a "new norm" for people which could prove important if more widespread use of masks was needed if there were any setbacks in pandemic control.
"Another benefit of mass masking over the winter months is the suppression of influenza and other respiratory viruses," they said.
"So mask use in winter will improve the efficiency of Covid-19 outbreak detection by reducing the amount of testing required."
There was also a potential benefit for the environment with people feeling safer using public transport rather than driving cars.
The researchers cited a range of new evidence backing the use of masks to limit transmission of the virus.
One review stated there was "modest evidence" to support widespread community use of universal masking to combat Covid-19, which included cloth masks.
"It will be important to examine evidence from countries such as China, Hong Kong and Singapore, where the majority of residents (as high as 98 per cent) use masks in public, and where to a significant extent, Covid was contained in combination with known effective strategies," the review stated.
Another study they cited suggested that a washcloth tied about the face could capture 99 per cent of droplets from a person's mouth – the main source of transmission for the virus.
However, it appeared unlikely the Government would be recommending Kiwis wear masks any time soon.
Its own review, requested by the Ministry of Health's chief science adviser Dr Ian Town, even cited some evidence to show that the physical properties of cloth masks – and notably the effectiveness of cleaning them, and the potential for them to retain moisture – could raise risk of infection.
"The majority of studies have not demonstrated benefit in cluster randomised controlled trials evaluating the effect of members of the general public wearing masks in non-healthcare settings to prevent the acquisition of viral respiratory infections," the review found.
"If masks are not used appropriately, and not combined with meticulous hand hygiene, there is a theoretical risk of increased infection risk through self-contamination."
In any case, any potential benefits of wearing masks were likely to be less effective than washing hands or physical distancing.