SAGE quietly released a document on January 13th which admits that masks are no protection for the wearer, are though intended to protect others aren’t even very good at that. An independent researcher has taken a closer look for Lockdown Sceptics and explains further.
SAGE released a document in January prepared by a sub-committee, which it endorsed, saying that masks were primarily a source control (cloth and surgical masks are thought to offer the wearer little protection) and citing an estimate for their typical impact on transmission of 6-15%.
That document says in relation to source control: “Analysis of regional level data in several countries suggest this impact is typically around 6 – 15% (Cowling and Leung, 2020, Public Health England 2021) but could be as high as 45% (Mitze et al., 2020).”
A 6 – 15% reduction seems to be a lot lower than NERVTAG, SAGE and the Government have previously suggested – barely relevant. Moreover, the Cowling & Leung paper says: “While most research on face masks has involved surgical type face masks, it should be presumed that reusable cloth masks could provide similar benefits if they have a sufficient number of layers and preferably a filter.” So the 6 – 15% estimate seems to be for surgical masks. Cloth masks in reality usually have few layers (maybe only one) and no filter. So their effect is likely smaller still.
The Cowling & Leung paper is here. It is an editorial not a research paper in its own right.
The 6 – 15% estimate actually comes from a December 2020 review paper by Brainard et al.
They say: “Conclusion: Wearing face masks may reduce primary respiratory infection risk, probably by 6-15%. It is important to balance evidence from RCTs and observational studies when their conclusions widely differ and both are at risk of significant bias. COVID-19-specific studies are required.” They also say “The environmental and economic costs of regularly using face masks are notable, and only partly abated by reuse.”