Face masks reduced the risk of respiratory infection
Research findings
|Published
Researchers at FHI have investigated whether using face masks outside the home protects against respiratory viruses. Previous international studies on face masks have suggested a correlation between mask usage and increased protection against respiratory infections, but many of these studies are small and have not provided conclusive answers. A recently published FHI study in the renowned journal BMJ shows clear results confirming that face masks have a protective effect against infection.
“Our results show that among those who used face masks, fewer people became ill. Nine percent of those who used face masks developed symptoms of respiratory infection, compared to 12 percent among those who did not use face masks. In practice, this means 3,300 fewer cases of infection per 100,000 inhabitants in Norway,” says Runar Solberg, researcher at the Center for Epidemic Interventions Research at the Norwegian Institute of Public Health.
- Read the study on Personal protective effect of surgical face masks in public spaces on self-reported respiratory symptoms in adults: pragmatic randomised superiority trial (dx.doi.org)
About the study
4,647 people were recruited to participate, and the study was conducted between 10 February and 27 April 2023. The study was randomized, meaning the participants were randomly assigned to two groups. This was done to ensure the two groups were comparable. Half of the participants (2,313 people) used face masks in crowded places outside the home, such as on public transport and in public spaces. The other half (2,262 people) did not use face masks.
Masks were not used at home or at work in either group. After two weeks, participants answered a short questionnaire asking if they had experienced cough, fever, or other respiratory infection symptoms.
“How can we know that no other factors than face masks – for example differences in infection rates different places, or that some participants have been more social than other – have come into play regarding infections or not among the participants?”
“Since this is a randomized study, other factors will be evenly and randomly distributed due to the number of participants. Over 4,000 participants is enough to be quite certain of the effect of face masks found in this study,” says Runar Solberg at the Center for Epidemic Interventions Research at the Norwegian Institute of Public Health.
The results are important for both society and individuals
For health authorities, it is important to have good knowledge about the effectiveness of face masks to provide sound advice to the public. Many people will also be interested in knowing how well face masks protect when considering whether it is worth the effort to use them.
“What we now know about the protective effect of using face masks suggests that it may be sensible to use them, along with following general infection control advice such as maintaining distance, especially if there is a high level of infection in circulation,” says Runar Solberg at the Center for Epidemic Interventions Research at the Norwegian Institute of Public Health.
Using face masks can help prevent you from infecting others when you are sick. This study only examined how well face masks protect against being infected by others.
Potential sources of error
A potential source of error is that there was some dropout during the study. The dropout was 20,7 percent in the group wearing face masks, and 13,7 percent in the control group.