Face masks may be inadvertently giving people Covid-19 immunity and making them get less sick from the virus, academics have suggested in one of the most respected medical journals in the world.
The commentary, published in the New England Journal of Medicine, advances the unproven but promising theory that universal face mask wearing might be helping to reduce the severity of the virus and ensuring that a greater proportion of new infections are asymptomatic.
If this hypothesis is borne out, the academics argue, then universal mask-wearing could become a form of variolation (inoculation) that would generate immunity and “thereby slow the spread of the virus in the United States and elsewhere” as the world awaits a vaccine.
It comes as increasing evidence suggests that the amount of virus someone is exposed to at the start of infection - the “infectious dose” - may determine the severity of their illness. Indeed, a large study published in the Lancet last month found that “viral load at diagnosis” was an “independent predictor of mortality” in hospital patients.
Wearing masks could therefore reduce the infectious dose that the wearer is exposed to and, subsequently, the impact of the disease, as masks filter out some virus-containing droplets.
If this theory bears out, researchers argue, then population-wide mask wearing might ensure that a higher proportion of Covid-19 infections are asymptomatic.
Better still, as data has emerged in recent weeks suggesting that there can be strong immune responses from even mild or asymptomatic coronavirus infection, researchers say that any public health strategy that helps reduce the severity of the virus - such as mask wearing - should increase population-wide immunity as well.
This is because even a low viral load can be enough to induce an immune response, which is effectively what a typical vaccine does.