Study by the Max Planck Institute: Minimal risk of infection with FFP2 mask

Danger of infection only in the per mil range: A new study shows how effective FFP2 masks are – if they are worn correctly. Without a mask and even with a lot of distance, the risk of infection is almost 100 percent.

FFP2 masks offer an extremely high level of protection against corona infection. This is the result of a study by the Max Planck Institute. If an infected and a healthy, unvaccinated person meet in an indoor area at a short distance, the risk of infection is only 0.1 percent even after 20 minutes. If the person is vaccinated, the risk of infection decreases even further, say the researchers.

Masks have to fit properly

However, according to the researchers, it depends on the correct way of wearing the FFP2 or KN95 mask. For optimal protection, the nasal clip must therefore be shaped into a “rounded W” so that it presses laterally on the nostrils. With poorly fitting FFP2 masks, the risk of infection in the same scenario is around four percent, writes the team around institute director Eberhard Bodenschatz in the “Proceedings” of the US National Academy of Sciences (PNAS).

The researchers’ analysis also shows that tightly fitting FFP2 masks protect 75 times better than well-fitting surgical masks. Nevertheless, even medical masks with a good fit reduce the risk of infection to a maximum of ten percent.

Extensive influencing factors taken into account

The researchers calculated the risk of infection by combining various factors such as particle sizes, physics when exhaling, various mask types and the risk of inhaling coronaviruses. The researchers emphasize that their calculations are even very conservative. “In everyday life, the actual probability of infection is certainly ten to a hundred times smaller,” says Bodenschatz. Because the air that flows out of the mask at the edges is diluted. However, the researchers wanted to calculate the risk as conservatively as possible. “If even the greatest theoretical risk is small under these conditions, you are on the safe side under real conditions,” says Bodenschatz.

Without a mask there is a high risk of infection

This is in contrast to the result of encounters between two people who are not wearing a mask: If, in this case, a healthy person stands three meters away in the breath of an infected person for a few minutes, there is a 90 percent probability that they will be infected Researcher.

“We would not have thought that at a distance of several meters it would go so quickly until you absorb the infectious dose from the breath of a virus carrier,” says Bodenschatz. Because at this distance, the air you breathe has spread conically in the room and the infectious particles have been thinned accordingly. The particularly large and therefore particularly virus-rich particles also fall to the ground after a short distance through the air.

“Nevertheless, in our study we found an enormous risk of infection even at a distance of three meters if you meet infected people with a high viral load, as occurs in the predominant delta variant of the SARS-CoV-2 virus, for a few minutes and does not wear a mask, “says Eberhard Bodenschatz. The results showed once again that wearing a mask in schools and also” in general is a good idea. “

Source: Tagesschau.