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VERIFY: Can weakened immune systems contribute to breakthrough cases?

A WCNC Charlotte viewer wanted to know whether people with compromised immune systems are becoming breakthrough cases at higher rates.

CHARLOTTE, N.C. — People in the U.S. with weakened immune systems can now get a third dose of the mRNA COVID-19 vaccines. Health officials making the decision late last week, saying this group might not have responded as well to the shots as others.

So, how many cases are in fully vaccinated, but immunocompromised people?

The Question

WCNC Charlotte viewer Ellen L. first posed this question, asking if breakthrough cases were happening more in people with compromised immune systems.

"I would like to know if the breakthrough cases of covid (among people who are fully vaccinated) are occurring in higher numbers in people with compromised immune systems?" Ellen wrote.


  • The Centers for Disease Control and Prevention
  • Dr. David Priest, Infectious Disease Specialist with Novant Health

The Answer

Compared to their share of the population, people with compromised immune systems are seeing breakthroughs at higher rates, which is why health leaders prioritized additional doses for them first.

"People that have problems with their immune system, either they have a medical condition that causes it or they take medication for another medical condition that causes it--they just typically don't respond to vaccines in the same way," Priest said.

According to the CDC, immunocompromised people make up less than 3 percent of the U.S. adult population, but in small studies have made up around 40 percent of breakthrough cases requiring hospitalization.

The agency also says various studies show the type of immunocompromising condition could make a difference in antibody response, with organ transplants, blood-related cancers and immune-suppressing therapies causing the least robust responses in some studies.

Credit: CDC

That vulnerability despite vaccination is why federal health officials are recommending that third dose for these groups.

Additionally, the CDC reports 74% of all breakthroughs reported to it have been in those 65 years and older, and doctors are anticipating additional shots get expanded beyond the immunocompromised group.

"There are other individuals who are older, and sometimes their antibody levels fall over time, and that's another group we think might benefit from that third dose," Priest said.

VERIFY is dedicated to helping the public distinguish between true and false information. The VERIFY team, with help from questions submitted by the audience, tracks the spread of stories or claims that need clarification or correction. Have something you want VERIFIED? Text us at 704-329-3600 or visit /verify.

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