MESSAGE
| DATE | 2020-11-19 |
| FROM | Ruben Safir
|
| SUBJECT | Re: [Hangout - NYLXS] [ Docs ] Masking Mandates Part II
|
nytimes.com
A New Study Questions Whether Masks Protect Wearers. You Need to Wear
Them Anyway.
By Gina Kolata
6-7 minutes
Masks prevent people from transmitting the coronavirus to others,
scientists now agree. But a new trial failed to document protection from
the virus among the wearers.
Passengers on a tram in Aarhus, Denmark. The country required masks on
public transport in August, and in public indoor spaces just last month.
Credit...Bo Amstrup/Ritzau Scanpix, via Agence France-Presse — Getty Images
Researchers in Denmark reported on Wednesday that surgical masks did not
protect the wearers against infection with the coronavirus in a large
randomized clinical trial. But the findings conflict with those from a
number of other studies, experts said, and is not likely to alter public
health recommendations in the United States.
The study, published in the Annals of Internal Medicine, did not
contradict growing evidence that masks can prevent transmission of the
virus from wearer to others. But the conclusion is at odds with the view
that masks also protect the wearers — a position endorsed just last week
by the Centers for Disease Control and Prevention.
Critics were quick to note the study’s limitations, among them that the
design depended heavily on participants reporting their own test results
and behavior, at a time when both mask-wearing and infection were rare
in Denmark.
Coronavirus infections are soaring throughout the United States, and
even officials who had resisted mask mandates are reversing course.
Roughly 40 states have implemented mask requirements of some sort,
according to a database maintained by The New York Times.
Dr. Anthony Fauci, director of the National Institute of Allergy and
Infectious Diseases, advocates a national mask mandate, as does
President-elect Joseph R. Biden Jr.
“I won’t be president until January 20th, but my message today to
everyone is this: wear a mask,” Mr. Biden recently wrote on Twitter.
From early April to early June, researchers at the University of
Copenhagen recruited 6,024 participants who had been tested beforehand
to be sure they were not infected with the coronavirus.
Half were given surgical masks and told to wear them when leaving their
homes; the others were told not to wear masks in public.
At that time, 2 percent of the Danish population was infected — a rate
lower than that in many places in the United States and Europe today.
Social distancing and frequent hand-washing were common, but masks were not.
About 4,860 participants completed the study. The researchers had hoped
that masks would cut the infection rate by half among wearers. Instead,
42 people in the mask group, or 1.8 percent, got infected, compared with
53 in the unmasked group, or 2.1 percent. The difference was not
statistically significant.
“Our study gives an indication of how much you gain from wearing a
mask,” said Dr. Henning Bundgaard, lead author of the study and a
cardiologist at the University of Copenhagen. “Not a lot.”
Dr. Mette Kalager, a professor of medical decision making at the
University of Oslo, found the research compelling. The study showed that
“although there might be a symbolic effect,” she wrote in an email, “the
effect of wearing a mask does not substantially reduce risk” for wearers.
Other experts were unconvinced. The incidence of infections in Denmark
was lower than it is today in many places, meaning the effectiveness of
masks for wearers may have been harder to detect, they noted.
Participants reported their own test results; mask use was not
independently verified, and users may not have worn them correctly.
“There is absolutely no doubt that masks work as source control,”
preventing people from infecting others, said Dr. Thomas Frieden, chief
executive of Resolve to Save Lives, an advocacy group, and former
director of the C.D.C., who wrote an editorial outlining weaknesses of
the research.
“The question this study was designed to answer is: Do they work as
personal protection?” The answer depends on what mask is used and what
sort of exposure to the virus each person has, Dr. Frieden said, and the
study was not designed to tease out those details.
“An N95 mask is better than a surgical mask,” Dr. Frieden said. “A
surgical mask is better than most cloth masks. A cloth mask is better
than nothing.”
The study’s conclusion flies in the face of other research suggesting
that masks do protect the wearer. In its recent bulletin, the C.D.C.
cited a dozen studies finding that even cloth masks may help protect the
wearer. Most of them were laboratory examinations of the particles
blocked by materials of various types.
Susan Ellenberg, a biostatistician at the University of Pennsylvania
Perelman School of Medicine, noted that protection conferred by masks on
the wearer trended “in the direction of benefit” in the trial, even if
the results were not statistically significant.
“Nothing in this study suggests to me that it is useless to wear a
mask,” she said.
Dr. Elizabeth Halloran, a statistician at Fred Hutchinson Cancer
Research Center in Seattle, said the usefulness of masks also depends on
how much virus a person is exposed to.
“If you show this article to a health care provider who works in a Covid
ward in a hospital, I doubt she or he would say that this article
convinces them not to wear a mask,” she said.
But Dr. Christine Laine, editor in chief of the Annals of Internal
Medicine, described the previous evidence that masks protect wearers as
weak. “These studies cannot differentiate between source control and
personal protection of the mask wearer,” she said.
Dr. Laine said the new study underscored the need for adherence to other
precautions, like social distancing. Masks “are not a magic bullet,” she
said. “There are people who say, ‘I’m fine, I’m wearing a mask.’ They
need to realize they are not invulnerable to infection.”
--
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