Swedish researchers recommend use of face masks based on studies

A Swedish study highlights the efficacy of face masks in reducing the spread of infectious viral diseases, with its authors saying masks should be encouraged wherever social distancing is not possible, including in Sweden.

Swedish researchers recommend use of face masks based on studies
Face masks have not been recommended to the general public in Sweden. Photo: Erik Simander/TT

A group of researchers from Sweden's Karolinska Institute and Canada's McMaster University, led by nephrologist Catherine Clase, reviewed 25 published studies into cloth face masks, and their filtration ability. 

“We were concerned about the debate created worldwide on the effectiveness of face masks,” Karolinska Institute epidemiology professor Juan Jesus Carrero, one of the authors of the study which was led by McMaster University professor Catherine Clase, told The Local.

“We settled to study, interpret and summarise the evidence there is to date evaluating whether face masks can protect from spreading and from being infected by viruses. We identified 25 articles that dealt with this problem, some of them almost 100 years old. We took a great amount of time in studying them, and in some cases re-analysing their data with modern or more appropriate statistics.”

Taken as a whole, the researchers say the findings are convincing enough to recommend wearing face masks as a disease control measure.

“We observe that the efficacy of filtration varies, sometimes less good, sometimes as good as a medical mask. However, they always offer some non-negligible degree of protection,” Carrero explained.

The virus causing Covid-19 has a similar diameter to many other viruses, he said, and although cloth cannot stop isolated virions, it can stop the larger particles caused by speaking, sneezing or eating, which the epidemiologist said were responsible for most virus transmission. 

Sweden's Public Health Agency has not recommended mask-wearing by the general public, even while the majority of countries around the world have done so as a measure to curb the spread of the coronavirus. Swedish authorities have said the lack of conclusive scientific proof is one reason.

The World Health Organisation (WHO) and other national governments have stressed the importance of wearing masks as a complementary measure to other actions, such as hand hygiene and social distancing.

State epidemiologist Anders Tegnell told The Local on Tuesday: “That report is saying the same thing as numerous reports from earlier on, that cloth masks will stop droplets from coming through to a certain extent. If that can be translated into some kind of effect in the community, the authors say they don't know.”

He said Sweden was not considering reviewing its guidelines on face masks in the current situation, but would look at them again if the development of the epidemic worsens in Sweden.

Another concern that Tegnell has raised is that mask-wearing may encourage people to relax on other more crucial measures, for example keeping distance to a lesser extent or touching their faces more.

“Face masks are just one piece of the puzzle that should never substitute hand hygiene, social distancing or disinfection of public areas. It is true that an incorrect use of face masks may diminish their efficiency, but that is something that can be corrected by educating the population on how to put face masks on, how to wear them and put them off, how to wash them or dispose of them,” Carrero said.

The researchers behind the literature review emphasised that their findings show the efficacy of the masks is also affected by how they are made, cleaned and used. Among the most protective materials, according to the study, were muslin, cotton and flannel masks, especially those in three or four layers and with a thread count of at least 100 threads per inch.

They also produced suggestions on how to make, clean and wear cloth masks based on the findings, which are currently available in English at The full study can be found here.

Member comments

  1. It’s very unfortunate how many closet racists in Stockholm. I was wearing a mask in a bus during busier hours. Instead of being left alone, many older people would scold me for being dramatic, young ppl making racist remarks saying I brought in the virus to Sweden (I’m a Canadian with partial Chinese heritage), and some passive aggressive remarks from service workers telling me if I feel slightly unwell I should stay home instead of going out with a mask. What a hypocrite country this is.

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Public Health Agency recommends two Covid doses next year for elderly

Sweden's Public Health Agency is recommending that those above the age of 80 should receive two doses of a Covid-19 vaccine a year, once in the spring and once in the autumn, as it shifts towards a longer-term strategy for the virus.

Public Health Agency recommends two Covid doses next year for elderly

In a new recommendation, the agency said that those living in elderly care centres, and those above the age of 80 should from March 1st receive two vaccinations a year, with a six month gap between doses. 

“Elderly people develop a somewhat worse immune defence after vaccination and immunity wanes faster than among young and healthy people,” the agency said. “That means that elderly people have a greater need of booster doses than younger ones. The Swedish Public Health Agency considers, based on the current knowledge, that it will be important even going into the future to have booster doses for the elderly and people in risk groups.” 


People between the ages of 65 and 79 years old and young people with risk factors, such as obesity, diabetes, poor kidney function or high blood pressure, are recommended to take one additional dose per year.

The new vaccination recommendation, which will start to apply from March 1st next year, is only for 2023, Johanna Rubin, the investigator in the agency’s vaccination programme unit, explained. 

She said too much was still unclear about how long protection from vaccination lasted to institute a permanent programme.

“This recommendation applies to 2023. There is not really an abundance of data on how long protection lasts after a booster dose, of course, but this is what we can say for now,” she told the TT newswire. 

It was likely, however, that elderly people would end up being given an annual dose to protect them from any new variants, as has long been the case with influenza.