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On Wednesday, the CDC published new research that shows medical plus cloth masks, or tighter fitting masks, can reduce the spread of COVID-19 by over 90%.

During January 2021, the CDC conducted two experiments to see the effectiveness of double masking and knotting and tucking medical procedure masks. In the first, using a device to simulate a person coughing, scientists reviewed the following double masking combinations to gauge protection from aerosol particles (% of particles blocked in parens):

• three ply medical mask (42%)
• three ply cotton mask (44.3%)
• three ply cloth mask over a three ply medical mask (92.5%)

The second experiment used ten mask combinations to gauge how two modifications to medical procedure masks could reduce aerosol emission. These combinations included no masks, single masks, and knotting/tucking the mask. By knotting and tucking, the report meant masks where there was a way to tighten or tie a knot of the ear loop near the face. The research found transmission of COVID was reduced 83% in double-masked situations and 62.9% in situations when the individual wore a knotted mask.

Based on this research, the CDC emphasized the importance of wearing well-fitting masks. Wearing masks that fit closely and/or have two levels of different material protections greatly reduce infection. The report concludes:

Until vaccine-induced population immunity is achieved, universal masking is a highly effective means to slow the spread of SARS-CoV-2 when combined with other protective measures, such as physical distancing, avoiding crowds and poorly ventilated indoor spaces, and good hand hygiene. The data in this report underscore the finding that good fit can increase overall mask efficiency.

The report makes no definite policy requiring mask types. However, this research comes as some European countries are now requiring residents to wear medical masks in public to reduce the spread of the COVID-19, especially the new mutations.