Evidence shows that, yes, masks prevent COVID-19 – and surgical masks are the way to go

Laboratory and observational studies

People use masks to protect themselves from diseases contracted since the Manchurian plague epidemic in 1910.

During the coronavirus pandemic, the focus was on masks as a way to prevent infected people from contaminating the air around them – called source control. Recent laboratory evidence supports this idea. In April 2020, researchers showed that people infected with coronavirus – but not SARS-CoV-2 – exhaled less coronavirus RNA into the air around them if they wore a mask. A number of additional laboratory studies have also confirmed the effectiveness of the masks.

In the real world, many epidemiologists have looked at the impact of masking and masking policies to see if masks are helping slow the spread of COVID-19. An observational study – which means it was not a controlled study with people wearing or not wearing masks – published in late 2020 looked at demographics, testing, lockouts, and mask wear in 196 country. Researchers found that after controlling for other factors, countries with cultural norms or policies supporting the wearing of masks saw weekly coronavirus mortality per capita increase by 16% during epidemics, compared with a weekly increase of 62% in countries without mask wearing standards.

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Large-scale randomized mask wearing

Laboratory, observational and modeling studies have always supported the value of many types of masks. But these approaches are not as robust as large-scale randomized controlled trials among the general public, which compare groups after the intervention has been implemented in some randomly selected groups and not implemented in the groups. comparison. Such a study done in Denmark in early 2020 was inconclusive, but it was relatively small and relied on participants to self-report mask wear.

From November 2020 to April 2021, my colleagues Jason Abaluck, Ahmed Mushfiq Mobarak, Stephen P. Luby, Ashley Styczynski and myself – in close collaboration with partners from the Bangladeshi government and the research association Innovations for Poverty Action – have conducted a large-scale randomized study. controlled trial on masking in Bangladesh. Our goals were to learn the best ways to increase warrantless mask wear, understand the effect of mask wear on COVID-19, and compare cloth and surgical masks.

The study involved 341,126 adults in 600 villages in rural Bangladesh. In 300 villages, we did not promote masks and people continued to wear masks, or not, as before. In 200 villages we promoted the use of surgical masks, and in 100 villages we promoted cloth masks, testing a number of different awareness strategies in each group.

For eight weeks, our team distributed free masks to every adult in the mask groups at their homes, provided information on the risks of COVID-19 and the value of wearing the mask. We also worked with community and religious leaders to model and promote the wearing of masks and hired staff to walk around the village and politely ask people who were not wearing masks to put one on. Plainclothes staff recorded whether people wore masks correctly over their mouths and noses, incorrectly, or not at all.

Five weeks and nine weeks after the start of the study, we collected data from all adults on symptoms of COVID-19 during the study period. If someone reported symptoms of COVID-19, we took and tested a blood sample to look for evidence of infection.

Wearing a mask reduces COVID-19

The first question my colleagues and I had to answer was whether our efforts had led to an increase in mask wear. Mask use more than tripled, from 13% in the group that did not receive masks to 42% in the group that received them. Interestingly, physical distancing also increased by 5% in the villages where we promoted masks.

In the 300 villages where we distributed any type of mask, we saw a 9% reduction in COVID-19 compared to villages where we did not promote masks. Due to the small number of villages where we promoted cloth masks, we were unable to say whether cloth or surgical masks were more effective in reducing COVID-19.

We had a sample large enough to determine that in the villages where we distributed surgical masks, COVID-19 fell by 12%. In these villages, COVID-19 fell by 35% for people 60 years and older and 23% for people 50 to 60 years old. Looking at COVID-19-like symptoms, we found that surgical and cloth masks resulted in a 12% reduction.

The body of evidence supports the masks

Prior to this study, there was a lack of baseline evidence on the effectiveness of masks in reducing COVID-19 in everyday life. Our study provides strong and real evidence that surgical masks reduce COVID-19, especially for older people who face higher death and disability rates if infected.

Policymakers and public health officials now have evidence from labs, models, observations and real trials that support wearing masks to reduce respiratory illnesses, including COVID-19. Since COVID-19 can so easily spread from person to person, if more people wear masks, the benefits increase.

So the next time you’re wondering if you should wear a mask, the answer is yes. Cloth masks are probably better than nothing, but high-quality surgical masks or masks with even higher filtration efficiency and a better fit – such as the KF94, KN95 and N95 – are the most effective at preventing COVID-19.

This article is republished from The Conversation, a nonprofit news site dedicated to sharing ideas from academic experts. It was written by: Laura (Layla) H. Kwong, University of California, Berkeley.

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Laura (Layla) H. Kwong does not work, consult, own shares, or receive funding from any company or organization that would benefit from this article, and has not disclosed any relevant affiliation beyond his university position.