Yes, You Should Still Wear a Mask After Getting Vaccinated (For Now)

Vaccines are over 95% effective, but other precautions must be taken

Photo by Mika Baumeister on Unsplash

Slowly but surely, people around the world are getting their first doses of the vaccine, and a handful more have received the second as well. Those who are lucky enough to be fully immunized, however, must continue wearing masks and socially distance, according to the Centers for Disease Control and Prevention (CDC).

Given all the good things that have been said about the effectiveness of the Pfizer/BioNTech and Moderna vaccines, even against the emerging variants, this may seem counterintuitive. But there are a number of reasons why these precautions are still necessary for now.

The first has to do with the effectiveness of the vaccines. Both that of Pfizer/BioNTech and Moderna are 95% effective, which means that it’s 95% likely that it will work in people. Wearing a mask and socially distancing is a way to protect people on the small chance that the vaccine does not work. As Brown University Medicine emergency doctor Megan Ramney, MD, MPH put it recently on Twitter, community transmission remains high in the United States, and “although the mRNA vaccines are remarkably effective, nothing in life is 100%.” Also, it takes time for a vaccine to become fully effective in the body — it’s not as if a person becomes immune the moment they receive their second dose. Masking and distancing help protect vaccinated people from getting sick during this time.

The second and perhaps less intuitive reason is that it’s possible that a person who is vaccinated might still be able to carry and transmit the virus. A vaccine’s effectiveness is based on its ability to protect against symptomatic disease — that is, whether a person will get sick if exposed to the virus — but not its ability to prevent infection and transmission. In other words, it’s possible that a vaccinated person who doesn’t show symptoms of Covid-19 can still be contagious. So, they must mask and distance themselves to protect people around them from getting sick, just in this case.

Last week, a team of scientists including infectious diseases expert Anthony Fauci, MD, explained this point in an article published in the journal Annals of Internal Medicine.

“Perhaps the unknown with the greatest potential immediate impact on the current pandemic is the degree to which these vaccines protect against infection and transmission,” they wrote. While the protective efficacy of the vaccines against symptomatic disease is known, they note that protection “from actual infection may be considerably less, whereas protection from severe disease may be considerably higher.”

The good news is that experts are looking into it. Specifically, the authors write, researchers are looking through the phase 3 trial data for evidence of people who were vaccinated and asymptomatically infected. (To do that, they’re looking to see whether asymptomatic people shed the virus and whether they developed antibodies to viral proteins that weren’t part of the vaccine.) So far, preliminary data from Moderna suggest that the vaccine offers some protection against infection and transmission, but there’s a lot more research to be done.

Understanding the difference between protection against symptomatic disease and protection against infection is important when thinking about achieving herd immunity. The popular thinking is that if enough people get vaccinated, herd immunity will be reached because enough people will be immune and transmission will stop. But that outcome isn’t guaranteed because it’s not known whether the vaccine can stop transmission.

“Failure to appreciate this distinction may lead to a false sense in vaccines that they are protected from infection and thus cannot transmit to susceptible contacts,” the authors write. “Hence, it is critical to continue to reinforce the public health measures of social distancing, hand-washing, and masking until the current outbreak is under control.”

The promising news is that this won’t have to last forever — as more people get vaccinated, vaccine-induced herd immunity will eventually be reached. And as researchers learn more about the vaccines’ effectiveness against transmission, they will get a better sense of the percentage of people who will need to be vaccinated to reach herd immunity and learn how the first wave of vaccines can be improved upon, if necessary.

In the meantime, wear a mask (double up if you can for added protection against more transmissible variants), socially distance, and calmly explain to friends and family why it’s necessary to do so, even for vaccinated folk — it isn’t the easiest explanation to grasp, so a little patience can go a long way.



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Yasmin Tayag

Yasmin Tayag


Editor, Medium Coronavirus Blog. Senior editor at Future Human by OneZero. Previously: science at Inverse, genetics at NYU.