Researchers from the nonprofit group Innovations for Poverty Action and several universities including UC Berkeley, Yale and Stanford Medical School took part in the first-ever large scale randomized controlled trial study examining the impact of mask wearing on COVID-19, which took place in Bangladesh.
The study, which began in June 2020, used a sample size of 341,830 adults from 600 Bangladeshi villages, according to Laura Kwong, campus assistant professor of environmental health science and a researcher for the study.
Kwong noted that while observational studies show that those who wore surgical masks had lower rates of COVID-19 than individuals who did not wear masks, such research is difficult to accurately interpret because mask-wearers may also be taking part in other initiatives to lower their risk of contracting the coronavirus.
“This study combines the power of causality in a controlled lab study with the advantages of a field study in which people act like people and don’t always wear masks correctly or consistently,” Kwong said in an email.
The researchers randomly assigned which villages they would promote mask wearing to, and some methods of promotion or “intervention” included letting people know about the importance of wearing masks over their mouths and noses and providing free masks, according to a Stanford Medicine press release.
As a result of the intervention, the researchers were able to triple the rates of community mask-wearing. Additionally, the mask-wearing intervention led to a 9% decrease in COVID-19 cases, Kwong noted in an email.
The researchers used the no-cost free mask distribution, offering information on mask-wearing, reinforcement in public and in person and modeling by trusted leaders, or NORM model, according to Innovations for Poverty Action’s website.
Kwong also said that based on the research team’s scaled analysis in India, Bangladesh, Nepal and Pakistan, the NORM model could have prevented 1.2 million official COVID-19 cases and more than 60,000 deaths.
The study was recommended to receive a grant by the nonprofit GiveWell, which funds research and charities.
According to Catherine Hollander, senior research communications officer at GiveWell, the study was recommended for four reasons.
The first was that the study filled a gap in scientific literature regarding whether community mask-wearing led to a reduction in COVID-19 cases. Additionally, promoting mask wearing is a low-cost behavior change.
“Face mask wearing is a low-cost behavior change with potentially positive health impacts relative to most countries in the world during the pandemic,” Hollander said.
Hollander also noted that at the time that grant was made in July 2020, worldwide mask wearing appeared low, showing that there was also room for growth and improvement. She added scientific advisers, policy makers and other officials also expressed an interest in the study.
Kwong noted the study’s results show unnecessary COVID-19 cases and deaths can be prevented by usage of “high-performance masks” in public and indoor places.