Are masks safe? If so, which masks should you use?
Researchers have provided a lot observational, model-based and laboratory evidence over the past year and half about the effectiveness of masks. It has been difficult for many to keep track of which masks work and which don't.
As an assistant professor in environmental health sciences, I have also wondered about these answers and led an earlier year study to determine which materials are the best.
Recently, I was part in the largest randomized controlled trial that has ever been conducted to test the effectiveness of mask-wearing. Although the study is still being peer reviewed, it has been very well received by the medical community.
We found evidence to support previous research that masks, especially surgical, prevent COVID-19.
Both observational and lab studies
Since the Manchurian plague of 1910, people have used masks to prevent them from contracting disease.
The focus during the coronavirus pandemic was on masks to prevent infected people from contaminating the air around them. This is known as source control. Recent laboratory evidence supports this notion.
Researchers discovered that coronavirus-infected people exhaled less coronavirus DNA into the air if they were wearing a mask in April 2020. Additional laboratory studies also support the effectiveness of masks.
Many epidemiologists have studied the effects of masking policies and mask-wearing to determine if masks can slow down the spread of COVID-19. In late 2020, one observational study, which was not controlled and did not include people wearing or without masks, looked at demographics, testing, lockdowns, and mask-wearing across 196 countries.
After adjusting for other factors, researchers discovered that countries that had cultural norms or policies that supported wearing masks saw their weekly coronavirus mortality rise by 16 percent during outbreaks compared to a 62 per cent weekly increase in countries that did not have mask-wearing regulations.
Large-scale randomized mask-wearing
Many types of masks have been proven to be effective in observational, modeling, and laboratory studies. These approaches aren't as robust as large-scale randomized controlled trials in the general population, which compare groups after an intervention has been performed in randomly selected groups.
A similar study was conducted in Denmark in the early 2020s. Although it was not conclusive, it was small and required participants to report their mask-wearing habits.
My colleagues Jason Abaluck and Ahmed Mushfiq Mobarak, Stephen P. Luby and Ashley Styczynski, in close collaboration, conducted a large-scale, randomized controlled trial of masking in Bangladesh from November 2020 to April 2021. Our objectives were to find the best methods to increase mask-wearing in Bangladesh without a mandate, to understand the effects of mask-wearing COVID-19 and to compare surgical and cloth masks.
Study participants included 341,126 adults from 600 villages in rural Bangladesh. We did not encourage mask wearing in 300 villages. People continued to wear masks or not as before. We promoted surgical masks in 200 villages, while cloth masks were promoted in 100 villages. Each village tested different outreach strategies.
Our team distributed masks free of charge to all adults in the mask groups. They also provided information about COVID-19, the benefits of mask-wearing, and their risks. We worked with religious and community leaders to promote the use of masks and also hired staff to go around villages asking people to don masks.
Plainclothes staff monitored whether people used masks correctly over their noses and mouths, or not at all.
We collected data on all adults who had symptoms of COVID-19 between five and nine weeks after the study began. We tested blood samples for evidence of infection if a person had COVID-19 symptoms.
Reduced COVID-19 for mask-wearing
My colleagues and I had to first ask if our efforts resulted in increased mask-wearing. The number of mask-wearers tripled from just 13 percent in the group who didn't have them to 42 percent in those who were. In villages where we promoted masks, physical distancing increased by 5 percent.
We saw a 9 percent decrease in COVID-19 in the 300 villages where any type of mask was distributed, compared to villages that did not. We were unable to determine whether surgical or cloth masks are better at reducing COVID-19 because there were only a few villages that we encouraged cloth masks.
The sample size was large enough to find that COVID-19 dropped by 12 percent in villages where we distributed surgical faces. COVID-19 dropped by 35% for those 60 and over and 23% for those 50-60 years. We found that both cloth and surgical masks had a 12 percent decrease in COVID-19-like symptoms.
Evidence supports the use of masks
There was no evidence to support the use of COVID-19-reducing masks in everyday life prior to this study. Our study supports the strong evidence that surgical masks can reduce COVID-19 in real life, especially for older adults who are more likely to die or become disabled from COVID-19.
Public health officials and policymakers now have the evidence from real-world trials, observation, lab models, and observations that mask-wearing can reduce COVID-19. Because COVID-19 is so easily transmitted from one person to another, more mask-wearers will reap the benefits.
If you're wondering if you should wear masks next time, the answer is yes. Cloth masks can be better than nothing. However, high-quality surgical masks (or masks with higher filtration efficiency and better fit, such as KF94s KN95s or N95s) are more effective in preventing COVID-19.
Laura (Layla) H. Kwong Assistant Professor of Environmental Health Sciences University of California, Berkeley
This article was republished by The Conversation under Creative Commons. You can read the original article.