Can You Spread COVID-19 After You've Been Vaccinated?

Although we have two vaccines that have been approved by the Food and Drug Administration to protect against COVID-19, experts warn we still need to follow precautionary procedures even after being vaccinated.

Both the Pfizer and Moderna COVID-19 vaccines have been proven to have over 90% efficacy against the virus in clinical trials, but scientists say we do not know if vaccinated people who show no symptoms of the disease can still spread the virus.

According to Popular Science, we must continue to wear masks, socially distance, and wash our hands even after getting the vaccine. Dr. Sandro Cinti, an infectious disease expert at the University of Michigan, said people who are vaccinated may still infect others.

"You have to wear your mask," he told CNN.

The clinical trials of the vaccine candidates only tracked those individuals who developed COVID-19 symptoms but since 40% of people are asymptomatic, you could still have the virus in your nose and infect others, Cinti said.

One of the reasons SARS-CoV-2, the virus that causes COVID-19, has been so transmissible is people can be contagious several days before they have any sign of illness, according to Popular Science. Although many vaccines such as those for measles and chicken pox prevent people from getting the disease and also prevent them from transmitting to others, scientists do not know if this is true for the COVID-19 vaccines that were developed at warp speed.

Some pathogens like the bacteria that causes whopping cough can infect and reproduce in people who have been vaccinated, even for short periods of time, although hopefully this will not be the case with the COVID-19 vaccines.

Data from the clinical trials of both the Pfizer and the Moderna vaccines show volunteers who received both doses of the vaccines had fewer asymptomatic infections than the placebo groups.

"Presumably, that means it also decreases the risk of transmission," said Dr. Susanna Naggie, associate professor of medicine at Duke University School of Medicine, according to Popular Science. "Maybe the vaccine completely prevents infection, or maybe it really shortens the period of infection and someone sheds for only a couple of days."

Experts say these are critical questions might be answered with the help of home testing kits, so Americans can track post-vaccination infections in their homes. Both Pfizer and Moderna have pledged to follow-up with their study participants to further investigate whether or not anyone became infected after being vaccinated.

"We are just getting access to the vaccine and so for some months to come we probably are still looking at questions about the role of the vaccine in transmission and the need to continue all these public safety health measures," said Naggie, who added, until we have adequate immunity in the U.S. and the answers to these questions, we still need to mask up.