A new study in The Lancet Results of a study show that masks significantly reduce the SARS-CoV-2 load in the breath exhaled by infected people. Reductions were as high as 98%, with variations depending on the type of mask worn.
This study is the first to measure viral shedding with and without a face mask in infected humans under real-world conditions of mask and respirator use. Previous studies only used mannequins. Study volunteers were not trained, fit tested, or given extensive instruction on the use of masks or respirators to maximize control of viral spread.
The net result is that the study largely replicates real-world conditions of mask selection and use. The measured viral load reductions are therefore representative of what would be expected in practice, without extensive efforts to adapt, test, and train the entire population in appropriate use.
Another strength of the study was the direct measurement of viral load in exhaled air, with and without a mask, in the same individual at the same time. Thus, each subject in the study served as a control. In addition, capturing exhaled virus made it possible to determine the particular strains of virus with which the study subjects were infected.
The study involved 106 volunteers between June 2020 and May 2022. Of these, 44 provided 60 pairs of same-day samples, one taken while wearing a face mask and one without, where at least one sample in the pair had detectable levels of SARS-CoV-2 virus.
The masks tested in the study were N95 and KN95 masks, cloth masks, and surgical masks. Study volunteers brought their own cloth masks when they were randomly assigned to wear a cloth mask. The vast majority of KN95 masks tested were those provided by the University of Maryland (where the study was conducted) to its students and staff. The surgical masks and N95 masks tested were also provided to the volunteers and thus largely represented a single brand of device.
The study evolved over time, from comparing cloth masks to surgical masks to comparing KN95 respirators to surgical masks to comparing KN95 respirators to N95 respirators. Of the 60 total matched samples, eight were produced with a cloth mask, 26 with a surgical mask, 13 with a KN95 respirator, and 13 with an N95 respirator.
The authors had already published previous results of the study. However, the current article in The Lancet includes for the first time the N95 and almost all KN95 results.
The researchers collected each sample over a 30-minute period using a human exhaled bioaerosol collector. The volunteers were asked to say certain phrases and sing at certain intervals during the 30-minute period to mimic the typical aerosols generated by vocalization.
The study found that wearing an N95 respirator mask resulted in the greatest reduction in exhaled viral load, an average reduction of 98%, significantly outperforming all other masks and respirators. KN95 respirators reduced viral load by 71%, cloth masks by 87%, and surgical masks by 74%. Cloth masks significantly outperformed both KN95 respirators and surgical masks. The difference in reduction between KN95 masks and surgical masks was not significant.
Overall, the study volunteers were a younger population with mild COVID-19. The Omicron variant of SARS-CoV-2 was by far the most common, detected in 29 samples. The Alpha and Delta variants were detected in 4 samples each.
Based on viral load measurements and previous studies of how much virus is typically needed to cause infection, the researchers estimated that wearing an N95 mask would reduce the likelihood of an infected person transmitting the virus by 20-fold.
The researchers explained the poor performance of KN95 masks in their study by pointing out that because they largely studied a single brand, the results are generally not representative of all KN95 masks. They noted that the brand of KN95 masks they studied had an unfortunate combination of stiffness and high resistance to airflow. The stiffness of the masks likely led to a poor fit, leaving large air gaps through which infectious aerosols could flow relatively unimpeded. The high resistance to airflow meant that air was more likely to flow through the gaps caused by poor fit rather than through the mask’s filters.
The study is limited in that it looked at younger individuals with milder disease. It also looked at specific mask manufacturers, so the results may not be generalizable to all N95, KN95, surgical, and cloth masks.
Nevertheless, the study demonstrated that all masks tested were effective in reducing infectious aerosols generated by people infected with SARS-CoV-2.
“The research shows that any mask is much better than no mask at all, and an N95 is significantly better than the other options. That’s the number one message,” said Dr. Donald Milton, lead author of the study.
The study provides strong evidence in support of policies that mandate mask-wearing as part of overall pandemic control measures. Mask-wearing is therefore an essential tool in any strategy to eradicate SARS-CoV-2.
The study authors themselves strongly recommend that healthcare professionals wear N95 respirators to protect their patients and visitors, as well as other healthcare workers.
“N95 duckbill masks should be the standard of care in high-risk situations, such as nursing homes and health care settings,” said Dr. Jianyu Lai, first author of the study.
The study further demonstrates the utterly unscientific nature of the Centers for Disease Control and Prevention (CDC) mask guidelines. The CDC also changed its guidelines last March, from 10 days of mask wearing after ending isolation due to COVID infection to just five days. Like previous changes, this change in guidance was politically motivated and not supported by science.
The requirement for health care providers to wear masks has also been phased out nationwide as health departments and the health systems in which they work have dropped the requirement. The New York State Department of Health dropped the mask requirement for health care providers in May.
The study came as the North Carolina legislature overrode the governor’s veto of a mask ban in that state. Mask bans are also in various stages of consideration in New York, Chicago and Los Angeles. Bills have been introduced in New York and Chicago, and in Los Angeles, the mayor has proposed a mask ban.
These mask bans are aimed at suppressing mass protests against genocide. Notably, North Carolina’s mask ban legislation also imposes liability on protest organizers for injuries that occur during protests and increases penalties for blocking roads during protests.
Only the working class can establish scientific control over Covid-19 and other infectious diseases, including by establishing a solid basis for mandatory mask-wearing. It must achieve this by taking power and implementing its own independent political program, which places social needs instead of private profit as the main economic engine of society.
