A data table from a CDC study has been taken out of context and misrepresented, and is being used to falsely suggest that people who wore masks became ill with COVID-19 more frequently than those who did not wear masks.
First and foremost, the CDC has clearly stated that “wearing a mask is intended to protect other people in case the mask wearer is infected, rather than the wearer.” Indeed, “my mask protects you and your mask protects me!” The fact that 70.6% of people in the study who were ill with COVID-19 reported ‘always’ wearing a mask says nothing about the mask-wearing habits of all the other people they came into contact with.
Second, health authorities have consistently said that masks are just one tool to help slow the spread of COVID-19. Mask use is most effective in preventing virus spread when it’s combined with social distancing and frequent hand washing (see CDC guidance here).
>>> Here are the key findings from the CDC study
“In this investigation, participants with and without COVID-19 reported generally similar community exposures, with the exception of going to locations with on-site eating and drinking options. Adults with confirmed COVID-19 (case-patients) were approximately twice as likely as were control-participants to have reported dining at a restaurant in the 14 days before becoming ill” (said the CDC study team).
In other words, more people who tested positive for COVID-19 reported going to a restaurant within 14 days of becoming ill, than those who tested negative. When in a restaurant setting, masks cannot be worn while eating and drinking, so the researchers concluded that eating and drinking at locations where mask use and social distancing cannot be maintained might be important risk factors for COVID-19.
Let’s look at how the researchers came to this conclusion. First, we have to look at the complete table, rather than just the excerpt used for the meme image.
This study was designed to look at 2 groups of people: those who tested positive for COVID-19 and those who tested negative. The study then researched behaviors in each group to learn why one group tested positive, but not the other.
This study included 154 people who tested positive for COVID-19 (‘Case’ patients) and 160 people with COVID-like symptoms who tested negative for COVID-19 (‘Control’ participants). The researchers asked both groups a series of questions (see the table on page 3).
The category of ‘community exposure’ questions asked each person how many times they did the following within the 14 days prior to feeling ill: go shopping, visit someone else’s home where there were less than 10 people inside, eat at a restaurant, spend time in an office setting, etc.
Notice that people who tested positive for COVID-19 were much more likely to have visited a restaurant in the two weeks before they became ill, compared to people who tested negative for COVID-19 (p-value=0.01, meaning a significant difference between the groups).
Those who went to a restaurant were also asked about the number of other people in the restaurant who were following recommendations like wearing a facial covering or mask, or social distancing.
The study found that COVID-19-positive people were more likely to report that other people in the restaurant were not wearing masks or following social distance recommendations compared to people who tested negative for COVID-19.
Patients were also asked how often they wore a face covering within the 14 days before they became ill. There were approximately equal numbers of people in the COVID-positive and COVID-negative groups who reported never, rarely, sometimes, often, or always wearing masks (p-value=0.86, indicating no significant difference between the groups). This means, mask wearing behaviors were the same between those who tested positive and those who tested negative, and cannot explain the difference in their COVID-19 diagnosis.
- People who tested positive for COVID-19 were more likely to have eaten in a restaurant where people were not wearing masks compared to people who tested negative for COVID-19.
- Because masks cannot be worn effectively while eating and drinking, the CDC study concluded that spending time indoors, with other people who are not wearing masks, increases the risk of contracting the COVID-19 virus.
Centers for Disease Control and Prevention. How to Protect Yourself and Others. Updated Nov 3, 2020. https://www.cdc.gov/coronavirus/2019-ncov/prevent-getting-sick/prevention.html
Centers for Disease Control and Prevention. The Morbidity and Mortality Weekly Report. Sept 11, 2020. Community and Close Contact Exposures Associated with COVID-19 Among Symptomatic Adults ≥18 Years in 11 Outpatient Health Care Facilities — United States, July 2020. https://www.cdc.gov/mmwr/volumes/69/wr/pdfs/mm6936a5-H.pdf
Centers for Disease Control and Prevention. Considerations for Wearing Masks. Updated Aug 7, 2020. https://www.cdc.gov/coronavirus/2019-ncov/prevent-getting-sick/cloth-face-cover-guidance.html