One question many people who are fully vaccinated for COVID-19 have is whether they can transmit the virus to someone who isn’t vaccinated.
For this to happen, it would mean the fully vaccinated person was asymptomatic. That term means being infected with the virus without ever knowing it.
While the COVID-19 vaccines have provided an opportunity to slow the spread of the virus, scientists are trying to learn just how much the vaccines can prevent transmission from occurring.
The good news is that data from the U.S. Centers for Disease Control and Prevention (CDC) shows while COVID-19 infections do occur in fully vaccinated people, these instances appear to be exceptionally rare.
“We do not have conclusive proof. But more and more studies and real-world evidence points to fully vaccinated people, who are not immunocompromised, are less likely to transmit the virus if they become infected,” said Brian Laird, PharmD, manager of Pharmacy Operations at OSF HealthCare Heart of Mary Medical Center in Urbana, Illinois.
How is that possible?
“The reason why is that vaccinated people have a lower viral load if they get infected,” Brian said.
Viral load means the amount of virus an infected person produces. If the viral load is significantly smaller because someone is fully vaccinated, that lessens the risk of transmitting the virus to others through the transmission of respiratory droplets.
So should fully vaccinated people be concerned about passing the virus to a friend or family member who is not vaccinated?
“Very few things in medicine have a zero percent chance of happening. But if the person is fully vaccinated and not immunocompromised for any reasons, there is less of a reason to be concerned about transmitting the virus if they become infected,” Brian said. “This is why the CDC has changed some guidance recently for fully vaccinated people.”
People who are immunocompromised and are fully vaccinated still are at risk of severe illness or hospitalization due to COVID-19 and should continue to wear a mask and practice other precautions.
How vaccines work
It’s important to remember how vaccines work. Many people don’t realize that vaccines primarily prevent the disease for which they were developed, but they don’t necessarily prevent infection.
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“In general, vaccines work by allowing your own body to produce antibodies — to mount a defense – against the disease for which you’ve been vaccinated. Your body then remembers what to do if it encounters pathogens from that disease in the future. When that happens, the immune system shuts down the virus before any damage is done,” Brian said. “No vaccine, however, is 100% effective in preventing the intended disease. As the number of people who get vaccinated increases, however, the more everyone’s risk of infection drops.”
There are a lot of questions about whether booster shots will be needed. While this is an area still being studied, Brian said in some ways it’s a good thing we don’t have the full answer yet.
“This means that antibodies are still present and haven’t fallen to an unacceptable level in individuals who participated in the early clinical trials,” Brian said. “But when a timeframe does pop up in the media, I would encourage everyone to add ‘at least’ in front of the number until the U.S. Food and Drug Administration and CDC recommend whether a booster shot is needed.”