Use of face mask helps prevent and control novel coronavirus spread. – Photo: Ragini Nair

If WHO, CDC and the U.S. Surgeon General were equally responsible for the public health message disaster of discouraging mask use by the public to cut the transmission risk of novel coronavirus, a paper published in PNAS tried to overcompensate for it with a highly unscientific work. Now, 35 scientists want the paper to be retracted.

If there can be 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 greatly 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 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.

Each one could have been addressed differently even while encouraging people to  wear a mask. Ramping up mask production could have addressed shortage, while lack of evidence on community transmission was taken as evidence of absence of community transmission by the CDC! WHO should have erred on the side of caution and encouraged face mask even while waiting for more evidence. That masks reduce the chances of virus spread is well known, even if evidence specific to novel coronavirus was not available.

How the messaging saga unfolded

Messages urging people not to wear a mask started in early February when the CDC Director Dr. Robert R. Redfield in a tweet on February 5 said: “CDC does not currently recommend the use of facemasks to help prevent novel coronavirus. 2019nCoV is not spreading in communities in the US. Take everyday preventive actions to help slow the spread of respiratory illness.”

Then on February 28, CDC tweeted: “CDC does not currently recommend the use of facemasks to help prevent novel coronavirus. Take everyday preventive actions, like staying home when you are sick and washing hands with soap and water, to help slow the spread of respiratory 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!” He continued: “The best way to protect yourself and your community is with everyday preventive actions, like staying home when you are sick and washing hands with soap and water, to help slow the spread of respiratory illness.”

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, WHO continued to discourage people from wearing a face mask. It said: “There is currently no evidence that wearing a mask (whether medical or other types) by healthy persons in the wider community setting, including universal community masking, can prevent them from infection with respiratory viruses, including COVID-19.”

It was only as recently as June 5 that WHO reversed its position on masks to protect individuals from coronavirus infection. “The use of masks is part of a comprehensive package of the prevention and control measures that can limit the spread of certain respiratory viral diseases, including COVID-19. Masks can be used either for protection of healthy persons (worn to protect oneself when in contact with an infected individual) or for source control (worn by an infected individual to prevent onward transmission),” the guidelines said.

Trying to overcompensate

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 with a completely unscientific work. 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 main finding of the paper was that masks significantly reduced infections while other mitigation measures, such as social distancing implemented in the U.S. were insufficient by themselves in preventing virus spread.

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”. Though Italy made face mask compulsory only 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.

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 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.

Published in The Hindu on June 27, 2020