CLAIM: A 2018 study that looked at the effectiveness of N95 masks versus medical masks found that masks don’t stop the spread of viruses.
THE FACTS: The study found that N95 masks and medical masks are equally effective at protecting against viral respiratory infections and illnesses -- not that masks do not work.
The trial tracked groups of health care workers who were randomly assigned to wear either N95 or medical masks, also known as surgical masks, when around patients with respiratory or influenza-like illness. It looked at the health outcomes of these health workers at 137 outpatient sites over four flu seasons.
Derek Cummings, a professor of biology and infectious disease epidemiologist at the University of Florida, said the study built on previous research that showed masks are effective at preventing the spread of viruses.
“The study was not designed to assess whether N95 masks work or not,” he said. “What we were trying to do was to say that we know N95s work. We don’t know how much better they are than medical masks.”
The study, which first appeared online in 2018 and then was published in the Journal of the American Medical Association in 2019, determined that both kinds of masks worked equally well. A line from the study’s conclusion reads in part: “neither N95 nor MM resulted in superior protection.”
Social media users shared screenshots of that section and falsely claimed it was evidence that masks do not work. Trish Perl, chief of the division of infectious diseases and geographic medicine at the University of Texas Southwestern Medical Center, also co-authored the study. Perl said she was mortified when she saw the misinformation about the study circulating online.
“We found there was not a difference between wearing a respirator and wearing a medical mask in that study,” she said. “We didn’t say masks don’t work or N95 masks don’t work.”
Since the start of the pandemic in 2020, misinformation around masks has been circulating online. Health officials, including the U.S. Centers for Disease Control, recommend masks to prevent those who are infected with coronavirus from spreading it.
— Associated Press writer Beatrice Dupuy in New York contributed this report.