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VERIFY: Moderna, Pfizer vaccines may prevent disease, but not infection

The two vaccines are supposed to either stop or lessen disease. But, they may not stop the virus from getting into your body.

WASHINGTON — We got a double dose of positive vaccine news this week. Both Moderna and Pfizer announced early returns from their vaccines show around 95% effectiveness.

RELATED: VERIFY: What is a Messenger RNA vaccine?

However, that effectiveness doesn’t mean the vaccines will prevent you from catching coronavirus.


Will the Pfizer and Moderna vaccines prevent you from getting infected with coronavirus?


The quick answer is, we don’t know and that isn’t a bad thing.

Our Sources:

Dr. Chris Beyrer, an Infectious Disease expert and Dr. William Moss, a vaccines expert both work at Johns Hopkins University.

Our Process:

It sounds alarming at first, neither vaccine is aimed at preventing you from getting an infection.

“These COVID vaccines are preventing clinical disease, we don't know if they prevent transmission,” Dr. Beyrer said.

It’s important to know the difference between infection and disease. Dr. Moss said just because you are infected or have transmitted coronavirus doesn’t mean you get sick.

“So you know, everyone who gets disease has an infection, and the infection causes the disease,” Dr. Moss said. “But not everyone who is infected has the disease.”

That is where Moderna and Pfizer have aimed their vaccines: preventing people from getting sick.

“What's being measured in the trials is whether or not they prevent disease, mild, moderate and severe disease,” Dr. Moss explained.

This isn’t rare for vaccines. Dr. Moss said most vaccines don’t actually stop a virus from entering your body.

“That requires a really strong kind of immune response to prevent infection,” he said.

Simply put, we don’t know if these vaccines prevent infection, but we do know their primary job is to stop the virus from becoming a disease or lessen the disease.

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