After much anticipation, the Centers for Disease Control and Prevention (CDC) has finally relaxed its guidelines on mask wearing—people who have been vaccinated need not wear a mask outdoors unless it is a crowded event. The action raises two questions: What took so long and did the CDC go far enough?
It has long been known that outdoor transmission of the SARS-CoV-2 virus that causes COVID-19—even in the absence of vaccines or a reservoir of people with natural immunity that follows recovery from COVID-19, is extremely rare—A Chinese study published in April 2020 identified 318 outbreaks that involved three or more cases and found that they all occurred in indoor environments, typically homes or transportation. Out of the 7,324 identified cases in China between the beginning of January to mid-February 2020 with sufficient contract tracing, there was only one outdoor transmission involving two people who had a face-to-face conversation.
A systematic literature review found that few COVID-19 infections occurred outdoors and that the odds of transmission is 19 times higher indoors compared to outdoors. Numerous public health experts have concluded that, outside of prolonged face-to-face contact with others, the risk of outdoor COVID-19 transmission is negligible. And while he was claiming as recently as the end of February that Americans may need to wear masks through 2022, Dr. Anthony Faucci conceded this past Sunday on ABC’s “This Week” that, “it’s pretty common sense now that outdoor risk is really, really quite low,” particularly if you are vaccinated.
Clearly, the CDC could have relaxed mask guidelines for outdoor activities a long time ago. Outdoor transmission was rare before vaccination started. But now that vaccination has become widespread, the CDC could have easily gone further.
Masks primarily protect others from infection by the mask wearer. They are less effective at protecting the mask wearer from being infected. The COVID-19 vaccines are highly effective at preventing the transmission of SARS-CoV-2. For the two-dose Pfizer and Moderna vaccines, which have comprised the nearly all of the vaccines administered in the U.S., a single dose is 80 percent effective and the second dose increases the effectiveness to over 90 percent. Anyone who has been vaccinated is unlikely to harbor the virus and pose a risk to others. In addition, most of the people they will encounter are likely already immune either from receiving the vaccine or from natural immunity.
Fifty-four percent of the population 18 and older have received at least one vaccine dose and 37 percent are fully vaccinated. What is perhaps even more important is that 82 percent of the especially vulnerable population 65 and older—who account for 81 percent of COVID-19 deaths—has received at least one shot and 66 percent are fully vaccinated. There have been about 32 million confirmed COVID-19 cases and the true number of cases is thought to be many times higher, which means that the true number of people with natural immunity could number in the hundreds of millions. Since only 12 percent of the confirmed cases fall in the under-18 age group, most of the people with natural immunity are likely 18 and older.
Vaccine and natural immunity are highly prevalent in the 18 and older population, therefore, there is little risk to them going mask-less outdoors. And the very low risk of outdoor COVID-19 transmission, made even lower by the fact that so many people are now immune, poses a miniscule risk to people under 18 for whom COVID-19 is not a severe disease—they comprise well under 1 percent of the COVID-19 hospitalizations and deaths.
The CDC could and should have acted sooner to relax its guidelines and should now direct that mask wearing outside is unnecessary for everyone unless they anticipate prolonged, face-to-face contact with others in large, crowded events. People who are at increased risk because of advanced age or medical comorbidities are always free to wear masks if they feel more comfortable and would be well advised to avoid risky settings whether indoors or outside. But most Americans, who have endured a year of restrictions and hardships, should no longer be burdened with masks in a setting where the science says it is safe.