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It seems contradictory, but two doctors at the University of California, San Francisco make it plausible: the masks protect against Covid-19 because they do not prevent all infections from the Sars-CoV-2 coronavirus.
Virologist Monica Gandhi and epidemiologist George Rutherford have published their opinion piece in the renowned “New England Journal of Medicine.” “It’s a theory,” Gandhi tweeted on Thursday, continuing: “Now we need more data.”
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What does the theory of the two doctors say? Bottom line: nose and mouth plugs are known not to offer 100% protection in everyday use. I can offer. Viruses can pass through the fabric barrier with fine droplets at the edge or through the fabric and infect other people wearing masks.
But the masks could reduce the amount of viruses that enter the body, suggest Gandhi and Rutherford. If only a few pathogens make the jump, this promotes asymptomatic processes in which infected people do not notice anything about their disease. And these asymptomatic courses are based on a response of the body’s defenses, which also persists as immunity to new infections.
Three advantages
Under the masks, therefore, the infection process could not be completely prevented, but could often be controlled to such an extent that the few infections that were not avoided are harmless for the affected people and even beneficial for the population: some Few fewer carriers, a little more herd immunity.
“We are not specifically proposing smallpox festivals here,” Gandhi writes. Doctors advise against consciously putting yourself or others at risk of infection, as well-meaning but misinformed parents sometimes do with their children to get rid of teething problems.
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“We’re just saying that wearing a mask is good in a number of ways,” says Gandhi. She mentions three advantages: it reduces transmission, milder disease processes, and increases immunity.
“Could wearing a mask be a simple vaccine until we have a real vaccine?” Asks the doctor. In the opinion piece, she and her colleague encourage further investigation of this possible effect: comparing the infection process in regions with and without mandatory mask and the antibody and immune cell responses of infected people with and without Covid-19 symptoms. .
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Unclear data
The fact that mask wearers are infected with small amounts of viruses in some cases is “an interesting hypothesis, but highly speculative and unproven,” said Julian Schulze zur Wiesch of the Science Media Center Germany.
It is indisputable that the use of masks, along with other measures such as keeping distance and washing hands, slowed the dynamics of the pandemic. However, there are still no reliable data on the influence of the amount of virus in the infection on the later course of the disease.
Experiments with mice have shown that in the case of influenza virus infections, the dose of infection can make the difference between life and death, with lower mortality and fewer viruses. Such results, as well as the findings from hamster studies cited in the op-ed, cannot simply be transferred to humans and Sars-CoV-2.
“There may be many reasons why more patients have a mild or asymptomatic course,” says the chief physician at the Hamburg-Eppendorf University Clinic. On the one hand, these patients are only found through the greatest number of tests and, on the other, relatively younger patients are infected, while at-risk populations, the elderly and previously ill people, are better protected today.
It is not clear whether a small amount of virus, as postulated, triggers a strong immune response.
Political dimension
Melanie Brinkmann of the Helmholtz Center for Infection Research in Braunschweig criticizes the second fundamental assumption in the opinion piece that mild or asymptomatic infections trigger long-lasting immune protection. “We see an immune response in people with mild courses, but the big question is how long they are protected,” says Brinkmann. Immunological studies would show if the assumption is correct, but only in many months.
“I don’t see any consequences for our behavior,” sums up Maria Vehreschild from the Frankfurt University Hospital. The article presented an expert opinion, but specifically collected data was not discussed. And it has already been proven that masks protect, “that is why they are part of the global hygiene concepts”, says the doctor. However, a possible additional positive effect is mentioned that could speak in favor of adhering to these hygiene concepts.
The magazine in which the op-ed was published is aimed at a professional American audience. “In this sense, this article must also be evaluated politically and is one more request for the use of masks”, says Julian Schulze zur Wiesch. There is no broad consensus in the US on wearing a mask.
The doctor recommends thinking in epidemiological contexts. When you wear a mask, it is about protecting people and yourself. Also, there could be a positive side effect that the upcoming flu season will be quite mild.
