As vaccines for coronavirus disease 2019 (COVID-19) become available, you might be hearing stories of a small number of people who were vaccinated and still tested positive for the virus, including a congressman from Massachusetts who had received both doses.
Fear not: This doesn’t mean the vaccines don’t work. Their job is to prevent serious illness and death, not necessarily mild or moderate infections. COVID-19 vaccines remain a significant step in helping end the pandemic and return to a more normal life where we can hug loved ones, celebrate milestones and travel more freely.
Here’s what you should know.
1. The vaccines take time to work.
It takes about two weeks for immunity to kick in after receiving your second dose (the two vaccines available now require two doses, spaced a few weeks apart), so you can still possibly become infected and pass the virus on to others as your body works on building its immune response.
You also might have been infected before you even got your shot. That infection can continue to develop after you get your shot, but before you are fully protected.
2. The vaccines protect against serious illness, but they may not prevent infection.
The vaccines work to keep you from getting infection that leads to symptoms and are particularly good at preventing severe illness. Although the vaccines are very effective in protecting you from symptomatic illness, we don’t yet know if they prevent you from spreading the virus to others if you don’t have any symptoms. In other words, if you get infected, it may not prevent you from spreading the virus to others.
The good news is that even though “it is possible to be infected with the COVID-19 virus after you’ve been vaccinated, your chances of becoming seriously ill are substantially lowered because you got the vaccine,” says UNC Health Chief of Infectious Diseases Joseph J. Eron Jr., MD.
3. The vaccines are very good—but not 100 percent effective.
None of the vaccines currently available are 100 percent effective. In clinical trials, the Moderna and Pfizer vaccines protected about 9 out of 10 people; this is considered a very good result.
Even so, vaccine developers are looking at ways to boost the effectiveness of vaccines, potentially with booster shots.
“Until we have more information, we have to assume that we have the potential to spread COVID-19 even if we’ve been vaccinated,” Dr. Eron says. “So that means we still have to take the precautions that we’ve talked about for so long: wearing a mask, washing our hands and physical distancing so that we keep others safe.”
Visit yourshot.org for the latest information on the COVID-19 vaccines.
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