A recent study in Denmark is getting a lot of attention: it indicates that wearing surgical masks (in Denmark, a place with low population density, at a time of low contagion) provides very limited benefits to the wearer. See article and original publication
Some commentators are jumping to the conclusion that masks are not effective. We believe that the study is accurate, has some limitation and provides limited new information. In particular the study was done at a time where Denmark had very low contagion rates, and were social distancing was in effect so surgical masks appeared to provide little added protection.
The study does confirm a few important facts:
Surgical masks are not designed as protective respirators
Surgical masks are not effective for self protection against COVID-19. They are designed to block fluids and have limited filtration performance, due to design and due to poor fit. In fact this and other studies shows that surgical masks are often worn incorrectly by most public users, with nose not covered, or just on the chin or with loose ear loops and leaks over nose, chin and cheeks. Half the above study participants wore their surgical mask improperly. That is useless indeed.
When worn properly their main benefit is to filter and slow the air you exhale, so in the event that you are contagious, they do protect the people around you. You can read our comparison of masks effectiveness.
Former CDC director Thomas Frieden wrote this week:
“An N95 mask is better than a surgical mask. A surgical mask is better than most cloth masks. A cloth mask is better than nothing,”
Wearing mask outdoor is of limited value
In places with low density of population, and provided people can maintain social distancing, wearing masks outdoor does not provide much benefits. In cities, authorities are mandating masks all the time to avoid confusion and problems in waiting lines (where social distancing is poor) and so that people do not manipulate their mask all the times when going in and out of shops.
But wearing a mask outdoor when you can maintain minimal social distancing is not useful. Most of contagions occur indoor. Outdoor contagion has only occurred via sustained closed contact in large gathering. So masks are a tool that works when there are risks and other tools do not work. Social distancing remains a very effective prevention method, but when it is not possible, a mask will protect you.
What to do ?
The advice of most medical experts remains the same:
- wear a mask indoor to protect yourself and others. That includes public transports which are a high risk activity.
- If you want to protect yourself during period of peak virus transmission, wear a FFP2 or N95 respirators. Surgical mask or fabric masks protect others mostly.
- if you are a person at risk, always wear a proper FFP2 or N95 respirator, fitted properly, when you are in public spaces and when you meet with extended family or relatives.
- Stay away from large gatherings.
- if you are walking or exercising outdoor, alone, in well ventilated area, you are safe, with or without mask. You may not be safe from getting fined but you are mostly safe from COVID-19.
- If you feel that you have any possible symptoms of flu or COVID-19, wear a mask, wear a mask and isolate yourself until you have been properly tested.
- Wash your hands, maintain public distancing. That is as important as wearing a mask.
And our last common sense advice is : choose a mask that you can wear properly and comfortably. Not all masks fit all people. Find a FFP2 or N95 mask that you are comfortable wearing for extended time.
Winter is here and there is hope we can beat COVID-19 by next autumn. It would be a shame if you are no longer with us at that time because you listened to some conspiracy theory online. Be responsible, be safe and see you next year.