Sep 20, 2021 15:00:00

Experiments in 600 villages show that 'wearing a mask' does reduce the number of people infected with COVID-19

'Wearing a mask' has been recommended worldwide as a way to prevent the spread of the new coronavirus infection (COVID-19) since the early days of the pandemic. Some may wonder, 'Is it really possible to control the infection by wearing a mask?', But a large-scale experiment with a total of more than 300,000 people living in Bangladesh villages. Published a pre-reviewed paper on the website of

the non-profit organization Innovations for Poverty Action , which showed that wearing a surgical mask suppressed the spread of COVID-19.

The Impact of Community Masking on COVID-19: A Cluster-Randomized Trial in Bangladesh | Innovations for Poverty Action
https://www.poverty-action.org/publication/impact-community-masking-covid-19-cluster-randomized-trial-bangladesh

The Impact of Mask Distribution and Promotion on Mask Uptake and COVID-19 in Bangladesh | Innovations for Poverty Action
https://www.poverty-action.org/study/impact-mask-distribution-and-promotion-mask-uptake-and-covid-19-bangladesh

Surgical masks limit covid-19 spread, say authors of Bangladesh study --The Washington Post
https://www.washingtonpost.com/world/2021/09/01/masks-study-covid-bangladesh/

Huge, gold-standard study shows unequivocally that surgical masks work to reduce coronavirus spread | Live Science
https://www.livescience.com/randomized-trial-shows-surgical-masks-work-curbing-covid.html

Many scientists have argued from the beginning of the pandemic that 'wearing a mask suppresses COVID-19 infection.' However, while it is possible to study the benefits of wearing a mask based on theory and simulation, it is difficult to study how wearing a mask can help prevent infection in the real world. Therefore, international research teams such as Yale University, Stamford University, and Bangladesh's non-profit organization GreenVoice have decided to conduct randomized controlled trials in the real world in 600 villages in Bangladesh.

In Bangladesh, it was mandatory to wear a mask from the end of May 2020, and although the offender was to be fined, the percentage of residents who actually wear it is about 26% as of June 2020. It was just that. Also, if you limit it to those who cover their nose and mouth tightly with a mask, the ratio has decreased to about 20%.

In the experiments conducted from November 2020 to April 2021, 300 randomly selected villages were designated as 'experimental groups' and a program was implemented to encourage them to wear masks, and the remaining 300 villages were designated as 'control groups'. No intervention was done. A total of more than 342,000 adults lived in the 600 villages surveyed, with approximately 178,000 assigned to the experimental group and approximately 160,000 assigned to the control group. It seems that there were 4000 people. The villages of the experimental group and the control group were similar in the number of COVID-19 cases, population, population density, etc. at the start of the test, and all the villages were at least 2 km away from each other.

The research team distributed free masks at homes and public places every week or every two weeks during the approximately eight-week intervention, and surgical masks were distributed to two-thirds of the villages in the intervention group. We distributed cloth masks to the remaining one-third. Also, at the time of distribution, a promotional video of wearing a mask featuring

former Bangladesh Prime Minister Sheikh Hasina and cricket star Shakib Al Hasan was shown, and Islamic religious leader Imam attended a worship on Friday. Interventions were made to encourage people to wear masks and to encourage people without masks to wear them through the 'Mask Promoter'.

As a result of the experiment, it was found that the mask wearing rate was only 13.3% in the control group without intervention, while the wearing rate was 42.3% in the intervention group, which was about three times higher. Not only was this result confirmed throughout the experiment, but even five months after the experiment was completed, the mask wearing rate in the villages of the experimental group was 10% higher. Furthermore, contrary to the concern that 'people who are relieved by wearing masks may shorten the social distance,' the percentage of residents who keep the social distance is 24.1% in the control group, compared to 24.1%. It was 29.2% in the intervention group.

We also investigated whether residents experienced symptoms such as COVID-19 and found that the intervention group had a nearly 10% lower rate of symptoms than the control group. In addition, a blood test of one-third of those who showed symptoms revealed that the COVID-19 positive rate in the intervention group was 9.3% lower than in the control group. In the villages where surgical masks were distributed free of charge, the rate of reporting COVID-19 symptoms decreased by 12%, while in the villages where cloth masks were distributed, the rate of decrease was only 5%.

'Our findings should not be interpreted as'wearing a mask can only prevent 10% of COVID-19 cases',' the research team said. This is because only '29 out of 100 people' have come to wear masks due to the intervention, and the percentage of people who wear masks is only 42.3% even in the intervention group. The research team argues that if the community's mask wear rate approaches 100%, the difference between the intervention group and the control group will be even greater.

Jason Abaluck, an economist and lead author of the paper at Yale University, said, 'This study basically ends the scientific debate on'whether masks are effective against COVID-19 at the collective level'. I think it will be. '