Science

To wear or not to wear a mask: a public health message disaster

Vital: Measures to cut the spread even minimally should have been encouraged.

Vital: Measures to cut the spread even minimally should have been encouraged.   | Photo Credit: ArtistGNDphotography

A paper projects the advantages of wearing face-masks, yet a group of scientists find the study methodology doubtful

If there is a single message delivered by leading institutions that can be considered as a disaster in public health messaging especially during a pandemic, then it is the advice to people not to wear a face mask. Especially during a pandemic, any non-pharmaceutical measure that cuts the transmission risk even by only a small percentage should have still been encouraged.

If acute shortage of masks for healthcare workers was the reason why the U.S. Surgeon General did not want the public to use a mask, the lack of community spread in the U.S. prompted the Centre for Disease Control (CDC) to discourage people from wearing it. For the World Health Organization, it was the lack of scientific evidence that masks can prevent coronavirus spread which prompted it to dissuade people from wearing a mask.

Messages urging people not to wear a mask started in early February when the CDC Director Robert R. Redfield in a tweet on February 5 said: “CDC does not currently recommend the use of face-masks to help prevent novel coronavirus. 2019nCoV is not spreading in communities in the US...”

CDC and WHO

On February 28, CDC tweeted: “CDC does not currently recommend the use of face-masks to help prevent novel coronavirus.

Take everyday preventive actions… to help slow the spread of illness.”

On February 29, the very next day after CDC’s tweet, the U.S. Surgeon General Dr. Jerome Adams weighed in on the issue. His message was largely unhelpful. He tweeted: “Seriously people – stop buying masks! They are not effective in preventing general public from catching coronavirus, but if healthcare providers can't get them to care for sick patients, it puts them and our communities at risk!”

In its interim guidelines, the WHO had on January 29 stated that in community settings, a “medical mask is not required by individuals without respiratory symptoms as no evidence is available on its usefulness to protect non-sick persons”.

In the guidelines updated on April 6, the WHO continued to discourage people from wearing a face mask. It was only as recently as June 5 that the WHO reversed its position saying masks protect individuals from coronavirus infection.

Unscientific approach

A paper published on June 11 in the Proceedings of the National Academy of Sciences (PNAS) tried to overcompensate by espousing the goodness of mask wearing through a completely unscientific approach. While the world media amplified the advantages of wearing a mask as projected by the paper, scientists were tearing up the study. Now, 35 scientists have written to the journal demanding the paper to be retracted.

The study had supposedly analysed the effects of mitigation measures in Wuhan, Italy and New York City. Besides a few factually wrong data and assumptions used to support their work, the paper has “serious methodological errors”. From the fact that Italy made face-mask compulsory on April 6 and New York City on April 17, the authors conclude that it reduced the number of cases by over 78,000 between April 6 and May 9 in Italy and over 66,000 in New York City from April 17 to May 9.

Call for retraction

The scientists calling for the retraction say that the authors have not factored in the “lag between changes in disease transmission and changes in reported case counts”. With the incubation period lasting for five-seven days, and at times up to 14 days, and another five to 10 days for symptoms to show up and testing to be carried out, the effect of mask in reducing the cases can be discerned only after a couple of weeks, thus completely weakening the study results.

The authors have wrongly used the dates of policy implementation as a proxy for actual mask use. Also, the policy mandating mask use was accompanied by other changes across the society, thus making it extremely difficult to tease out the effect of mask alone in reducing cases. The scientists also say only simple linear regression models have been used and no “measures of statistical uncertainty are measured or presented”. This becomes particularly egregious as the analysis is based on only three regions.

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Printable version | Jul 9, 2020 10:46:04 PM | https://www.thehindu.com/sci-tech/science/to-wear-or-not-to-wear-a-mask-a-public-health-message-disaster/article31934567.ece

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