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 Author: Anne Allred, Erin Richey (KSDK) Published: 10:57 PM CDT April 29, 2021 Updated: 10:57 PM CDT April 29, 2021 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.