In a commentary in New England Journal of Medicine, Monica Gandhi and George W Rutherford of University of California in San Francisco said face masks could work like variolation to generate immunity. and slow the spread of Covid infection.
Mask may provide vaccine-like effect: Doctor
This possibility is consistent, according to experts, with a long-standing theory of viral pathogenesis, which holds that the severity of the disease is proportionate to the viral inoculum (infecting amount of the virus) received.
Gandhi and Rutherford inferred that if the viral inoculum matters in determining the severity of Covid infection, an additional hypothesised reason for wearing facial masks would be to reduce the viral inoculum to which the wearer was exposed and the subsequent clinical impact of the disease. “Since masks filter out some virus-containing droplets (with filtering capacity determined by mask type), masking might reduce the inoculum that an exposed person inhales,” the pair wrote in NEJM.
An experiment conducted on hamsters supported this theory and showed with simulated masking that the animals were less likely to get infected, or were either asymptomatic or had milder symptoms than unmasked hamsters.
“The hopes for vaccines are pinned not just on infection prevention: most vaccine trials include a secondary outcome of decreasing severity of illness, since increasing the proportion of cases in which disease is mild or asymptomatic would be a public health victory. Universal masking seems to reduce the rate of new infections; we hypothesise that by reducing the rate of new viral infections, it would also decrease the proportion of infected people who remain asymptomatic,” Gandhi and Rutherford wrote.
They referred to an outbreak on a closed Argentinian cruise ship where passengers were provided with surgical masks and staff with N95 masks. The rate of asymptomatic infection was 81% on testing compared with 20% in earlier cruise ship outbreaks without universal masking.
Dr S K Sarin, director of Institute of Liver and Biliary Sciences, said this paper explained how 29% of Delhi were antibody-positive but have never had infection. “Mask may allow a very miniscule amount of virus to enter and provide a vaccine-like effect, leading to antibody formation without true infection,” said Sarin.
Sarin added that this made the use of masks a priority while permitting people to move around freely so that getting a small inoculum could act like vaccination. Gandhi and Rutherford did say in their research that adoption of population-wide masking was one reason why some countries fared better in terms of rates of severe Covid-related illnesses.
While face masks were immediately advised in India for protection against Covid in March, recent data have indicated that facial masks could also reduce the severity of the disease.