Face masks highly effective against Covid-19, new evidence suggests

Three separate studies find routine wearing of face masks can curb spread of coronavirus

Three new studies from Germany, Britain and the United States have indicated face masks are highly effective in stopping the spread of coronavirus from person to person.

The first study examined the city of Jena in Germany, which made it compulsory for residents to wear face masks in public places, such as on public transport and while shopping, on April 6th.

Scarves and improvised cloth coverings were allowed where purpose-made masks were not available, and medical-grade masks were reserved for health workers.

After the introduction of the mandatory masks, "the number of new infections fell almost to zero", noted the report, which was written by four academics working in Germany and Denmark and published by an independent research body, the Institute of Labor Economics (IZA).


“We believe that the reduction in the growth rates of infections by 40 per cent to 60 per cent is our best estimate of the effects of face masks . . . We should also stress that 40 to 60 per cent might still be a lower bound,” they write.

“The daily growth rates in the number of infections when face masks were introduced was around 2 to 3 per cent. These are very low growth rates compared to the early days of the epidemic in Germany, where daily growth rates also lay above 50 per cent. One might therefore conjecture that the effects might have been even greater if masks had been introduced earlier.”

By the end of April, all of Germany’s federal states had made the wearing of face masks mandatory, following normal practice in several Asian countries that successfully contained the disease early on.

Most effective measure

A second study was conducted by the US Centers for Disease Control and Prevention and examined a coronavirus outbreak on the USS Theodore Roosevelt.

It surveyed 382 people on the ship about what measures they had taken to protect themselves against the disease.

The results indicated that wearing a face covering was the most effective measure against the virus, followed by distancing, and avoiding common areas. Of those who did not wear a face covering, 81 per cent became infected, while among those who did wear a face covering, 56 per cent became infected.

Most studies stress that further research is needed to identify what kind of face covering is most effective, and note that a combination of hand-washing, distancing and other measures contribute to an overall reduction in spread alongside the wearing of face masks.

The British study was conducted by scientists at Cambridge and Greenwich universities, and found that even home-made masks can dramatically reduce transmission rates if enough people wear them in public.

According to the results, routine wearing of masks by more than 50 per cent of the public means that people who are infected with Covid-19 pass it on to only one person or less. This means that the number of infections will drop over time rather than rising exponentially, as happens when no preventative measures are taken.

The researchers found that if people wear face masks whether they have symptoms or not, it is twice as effective at curbing the spread of the disease than if people wear face coverings only after they begin experiencing symptoms.

Naomi O’Leary

Naomi O’Leary

Naomi O’Leary is Europe Correspondent of The Irish Times