Skip to main content

Uncovering Breakthrough COVID Cases

At this point in time, over half of the U.S. population has received the COVID-19 vaccine. So far, the vaccines have proven great effectiveness in preventing worse outcomes of the disease, especially the mRNA vaccines made by Pfizer-BioNTech and Moderna. While this is great news, COVID still remains a threat, vaccinated or not.

Although the COVID-19 vaccines are more than 90 percent effective, some rare cases of severe COVID have been reported in fully vaccinated people. While these rare reports are highly uncommon, they are not unanticipated. The Centers for Disease Control and Prevention (CDC) is currently identifying and investigating hospitalized and fatal breakthrough COVID cases.

What is a Breakthrough Case?

The CDC defines a COVID breakthrough case as a case involving a person who tested positive for the virus at least 14 days after becoming fully vaccinated, and hadn’t tested positive in the preceding 45 days. The two-week mark is important because at this point, your body should have had enough time to develop antibodies to the virus.

Breakthrough COVID cases are expected, like with other vaccines. While the COVID-19 vaccines have proven to be effective in controlling the pandemic and mitigating severe cases of the virus, no vaccine is 100 percent effective at preventing illness in vaccinated people. A small percentage of people will still be affected by COVID-19, and may be hospitalized or die.

Reporting and Investigating COVID Breakthrough

State health departments report COVID breakthrough cases to the CDC. The CDC monitors reported hospitalized or fatal breakthrough cases for clustering by patient demographics, geographic time, time since vaccination, vaccination type and SARS-CoV-2 lineage. Respiratory specimens that test positive for SARS-CoV-2 RNA are collected for genomic sequencing to identify the virus lineage that caused infection.

As of April 30, 2021, a total of 10,626 COVID breakthrough cases had been reported of approximately 101 million people in the U.S. that had been fully vaccinated against COVID-19. Some health departments may continue to report all COVID vaccine breakthrough cases to the national database, however the CDC is only focused on monitoring all hospitalized and fatal cases,  as of May 1, 2021. The CDC will no longer track mild COVID breakthrough cases.

According to Tom Clark, MD, MPH, deputy director of the division of viral diseases at the CDC and lead of the agency’s vaccine evaluation team, the rationale for this focal shift is to concentrate on cases that are of “most importance to public health.” The CDC’s priority is to understand the cases associated with severe disease.