COVID Breakthrough Cases Worrying, but Vaccine Hesitancy Is Worse: Experts

COVID infections in unvaccinated people pose a much bigger issue than breakthrough cases do, scientists have said.

Breakthrough cases, in which a fully-vaccinated person still ends up catching COVID, have made headlines recently with some restaurants having to close due to infections among vaccinated staff.

Dr. Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases, told NBC on Sunday it is "very clear" the U.S. needs to step up COVID testing when asked if the country was doing enough to track breakthrough cases.

But a number of experts have told Newsweek that while breakthrough cases are concerning and important to study, the vaccines continue to work very well in terms of preventing severe disease and that the bigger problem is still the huge number of unvaccinated individuals in the country.

"Infections in unvaccinated people are the bigger problem by far," said Kathleen Neuzil, director of the Center for Vaccine Development and Global Health at the University of Maryland School of Medicine. "They get infected more; they get sicker; and they likely transmit virus more readily."

Mark Jit, professor of vaccine epidemiology at the London School of Hygiene and Tropical Medicine, said that breakthrough cases are "a caution" that even vaccinated people can spread COVID.

But, he said, vaccinated people "are still a lot better protected against infection than unvaccinated people."

Why do breakthrough cases happen?

In simple terms, breakthrough cases occur because the immunity granted to someone by a vaccine is not strong enough to prevent the virus from getting into someone's body and replicating, said Dr. John Swartzberg, clinical professor emeritus of infectious diseases and vaccinology at the UC Berkeley School of Public Health.

As the CDC states, no vaccine is 100 percent effective in preventing illness. Breakthrough cases can and will happen, not just with COVID but in other illnesses too.

It can also be more difficult for the body to mount an immune response to certain viruses than for others, Neuzil said.

She told Newsweek: "Because of the entry of the virus into the respiratory tract—through the nose or throat—it can be difficult to mount an effective mucosal immune response to completely shut down infection."

Another possibility, said Neuzil, is that someone may have a compromised immune system that didn't mount a good immune response to the virus.

Variants have an impact, too. The U.S. is seeing more breakthrough infections with the highly-infectious Delta variant than with previous variants, said Swartzberg.

Should we be worried?

Breakthrough cases are not something to be ignored and, as Fauci has already suggested, warrant further study.

Jit told Newsweek that breakthrough cases are expected to increase and are "a warning that having two vaccine doses doesn't guarantee that you will never get COVID."

But such cases are not a sign that the vaccines aren't working or that vaccine hesitancy is not an issue. Asked if breakthrough cases warrant concern, Neuzil said: "Yes and no. The vaccine is doing what we want it to do—preventing severe disease and symptomatic disease.

"The vaccines aren't 'sterilizing' the nose from virus in all situations. Again, if I have virus in my nose, and I'm not very sick, the only danger is that I transmit the virus to others around me who aren't vaccinated. This is why we need more people to get vaccinated."

And Swartzberg said: "There is the risk of hospitalization and death with a breakthrough infection, but it is tremendously less than that seen in the unvaccinated.

"Almost all the hospitalizations and deaths are in the unvaccinated. It is more important than ever that people get vaccinated."

Nurse receives a COVID vaccine
A nurse gets a COVID vaccine at the Rocky Mountain Regional VA Medical Center in Aurora, Colorado, in December 2020. Breakthrough cases will occur as no vaccine is 100 percent effective, the CDC says. Michael Ciaglo/Getty

Editor's pick

Newsweek cover
  • Newsweek magazine delivered to your door
  • Unlimited access to
  • Ad free experience
  • iOS and Android app access
  • All newsletters + podcasts
Newsweek cover
  • Unlimited access to
  • Ad free experience
  • iOS and Android app access
  • All newsletters + podcasts