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VERIFY: The who and why of COVID-19 breakthrough cases

According to the CDC, more than 87 million people in the United States had been fully vaccinated as of April 20

ST. LOUIS — If you are infected with COVID-19 after being vaccinated, it is called a breakthrough case.

The 5 On Your Side Verify team consulted the following experts:

  • Dr. Anna Durbin, Department of International Health, Johns Hopkins Bloomberg School of Public Health
  • Dr. Rachel Presti, infectious diseases, Washington University School of Medicine
  • Centers for Disease Control and Prevention

Experts say there are some things they can confirm about breakthrough cases. The cases are rare, symptoms are mostly mild, it’s happening in all age groups and breakthrough cases happen with every vaccine.

“No vaccine will 100% prevent infection, and I think that’s a really important point to bring out,” Durbin said.

As to why these breakthrough cases are happening with the COVID-19 vaccines, that is still being studied.

Presti is co-leading a Washington University study looking into three possible reasons:

Her team hypothesizes breakthrough cases are happening because people aren't creating a robust antibody response to the vaccine, the virus mutates and becomes unrecognizable to the antibodies, or the COVID-19 exposure is so large that it overwhelms a patient’s immune response.

The experts all agree breakthrough cases should not deter people from getting vaccinated.

There is some evidence, according to the CDC, that vaccination may make illness less severe in patients who get vaccinated but still get sick.

The latest data from the CDC reports only .008% of Americans who are fully vaccinated have been infected with COVID-19.  

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