Even thoughare more than 90% effective at preventing serious illness, millions of vaccinated people will likely have a breakthrough infection, according to the Centers for Disease Control and Prevention.
Most of the cases so far have been mild, with few or no symptoms. Out of more than 160 million fully vaccinated people in the U.S., the CDC says 5,500 — mostly the elderly and people with underlying health conditions — have been hospitalized or died.
Dr. Paul Duprex, a vaccine researcher at the University of Pittsburgh, says it's crucial people get vaccinated against the coronavirus so there's less virus to mutate and spread.
"The significance of breakthrough infections is people who are vaccinated can pass it on," Duprex said. "What we should think about is not being that human petri dish, not allowing yourself to be the person that allows the virus to replicate out of control and change to the next virus of concern."
Dr. Anthony Fauci, the nation's top infectious disease expert, explained that breakthrough cases do not mean the vaccines are failing.
"It isn't that it doesn't protect against infection. It does have a high degree of protection against infection, but not nearly as high as the very high protection against severe disease," Fauci told "CBS Evening News" anchor and managing editor Norah O'Donnell. "Just because you're seeing breakthrough infections, that doesn't mean that it lessens the ability of that vaccine to protect you from severe disease."
Music lovers recently returned to Scranton, Pennsylvania's Peach Festival after it was canceled last year because of COVID-19. Geoff Friedman and Julie Greenhouse were among the fans crowded into an outdoor amphitheater for four days of high-octane music.
"It was a hippie fest where people were close and hugging and high-fiving," Friedman said.
There wasn't a mask insight in the crowd of 16,000. "It didn't really occur to us that, we were putting ourselves at risk. We were outside. We were all vaccinated," Greenhouse said.
But vaccinations were not required. Forty-eight hours after the last curtain call, Greenhouse — who is fully vaccinated — developed symptoms and tested positive for.
"I think if I had thought it through that I could have gotten COVID from someone unvaccinated, I would have been smarter," she said.
The next day, Friedman also tested positive, followed by 13 of their festival friends also having breakthrough infections. "We were lucky that the vaccine protected us and gave us only mild symptoms," Greenhouse said.