As the coronavirus vaccines are rolled out across the country, there have been some reports of fully vaccinated people still contracting COVID-19. Experts say these "breakthrough cases" are expected, and want to assure people the vaccines are still highly effective.
Clinical trial data showed that both the Pfizer-BioNTech and Moderna coronavirus vaccines were extremely effective in preventing disease, but Dr. Bill Moss, a pediatrician and professor of infectious disease epidemiology at the Johns Hopkins Bloomberg School of Public Health in Baltimore, noted that some people in the trials did contract the virus.
"95% efficacy is not 100% efficacy," said Andrew Heinrich, a lecturer at the Yale School Of Public Health in New Haven, Connecticut.
Most recently, the state of Oregon reported four cases of people who were diagnosed with the coronavirus after being fully vaccinated. All four cases were either mild or asymptomatic, which experts said is further proof that the vaccines are doing their job.
"There are going to be some people who are not protected, even by two doses of the vaccine, but they should have more mild disease," said Moss. "... The vaccines are really highly protective against severe disease, so even those who get COVID-19 after two doses of vaccine are much more likely to have mild disease."
Moss noted that right now, with high rates of transmission and thousands of COVID-19 cases being diagnosed daily, the amount of virus circulating in the United States is high, especially since it's fairly early in the vaccination process.
"Once community transmission starts going way down, we'll see fewer cases in general, and as a result, fewer (outbreaks)," he explained.
How can I avoid getting COVID-19 after being vaccinated?
Heinrich and Moss said that once you have been fully vaccinated — which means you've received both doses of the vaccine and waited two weeks after the second dose — you should still take the same precautions, like masking and social distancing in public.
"There's nothing different that people should be doing," said Moss. "... As more and more people get vaccinated here, as community transmission goes down further ... We will hopefully see a setting where we start reducing some of these public health measures, like masking, but we're not there yet. That's where I hope we will be in the coming months."
Heinrich said that an important thing people can do is urge their loved ones to get vaccinated as doses are available to them.
"Vaccines matter most when a significant portion of the population gets them," Heinrich said. "It's a bit of a logarithmic scale and (as more people get vaccinated,) the benefits start to mount immensely. The best thing you can do to make your vaccine as effective as possible for yourself and your family is to get everyone around you vaccinated as they become eligible."
Can I spread COVID-19 after being vaccinated?
According to Heinrich, the "jury is still out" on whether you can carry and spread COVID-19 after being vaccinated, but some studies on the topic appear to offer optimism.
Dr. Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases, said during a White House coronavirus response team briefing that early studies are "pointing in a very favorable direction." However, further studies will be necessary on the topic.
For now, public health experts are still advising that people wear masks and continue to social distance, even after being vaccinated, to make sure that they don't spread the virus to those who are not yet vaccinated.
CORRECTION (March 26, 10:30 AM): An earlier version of this article misstated Andrew Heinrich’s title as a professor at the Yale School of Public Health. He is a lecturer at the Yale School of Public Health, not a professor.