Fauci: Breakthrough infections after vaccinations 'inevitable'

It is inevitable that some people who have been fully vaccinated against the coronavirus will still get a "breakthrough" infection because no vaccine is 100 percent effective, Dr. Anthony Fauci said on Monday.

Video Transcript

ANTHONY FAUCI: I'd like to spend a few minutes now talking about the concept of breakthrough infections. Can I have the first slide? I think it'll be important to put this into perspective with some definitions. A breakthrough infection, or a vaccine failure, is when a person contracts an infection despite being vaccinated against it.

We see this with all vaccines. In clinical trials, and in the real world, no vaccine is 100% efficacious or effective, which means that you will always see breakthrough infections regardless of the efficacy of your vaccine. There's primary vaccine failure, when the body actually doesn't amount an adequate immune response, for a number of reasons, could be immune status, health status, age, medications you're on, was something wrong with the vaccine, storage, delivery, composition.

Secondary vaccine failure may occur when immunity fades over time. Now, a vaccine may fail, also, if a person is exposed to a new or different strain or a variant. For example, influenza is the most common of this, which mutates rapidly and drifts genetically, generally from season to season.

However, even if a vaccine fails to protect against infection, it often protects against serious disease.