Researchers at the Indian Institute of Science used synthetic cough droplets to model how well different mask types stand up to coronavirus particles.
They found that surgical and N95 masks are still the most effective at stopping coronavirus spread.
Cloth masks may be a suitable alternative if these masks only if they have at least three layers and are made of cotton, the team found.
These findings may be particularly useful for lower-income countries like India, where surgical masks are not easily accessible to the general population.
In fact, though, the study has not shown anything about the effectiveness of cloth masks to prevent infection. It is not a study of real-world transmission at all but a laboratory test of how masks stop synthetic droplets. These droplets are around 500 micrometres in diameter, so not aerosols, which are typically considered to be much smaller (certainly less than 100 micrometres and possibly less than five). It therefore hasn’t even considered how well the masks impede aerosol transmission, which is one of the main modes of transmission.
A recent study, the Bangladesh mask study, did look at the real-world effectiveness of cloth masks. It found a slight reduction from 0.76% antibody prevalence in control villages (no masks) to 0.74% prevalence in cloth mask villages, though this was not statistically significant. There were numerous problems with this study, not least than it was confounded by additional interventions (an awareness campaign) and did not properly measure initial antibody and prior infection levels. However, even with these limitations it still indicates very little discernible difference.
The Danish mask study, Danmask-19, found no statistically significant effect on infection from wearing surgical masks either. This is in line with pre-Covid evidence on the lack of effectiveness of masks in protecting from respiratory infection and transmission.
When will the mask zealots admit that their pet intervention is a dud?