September 13, 2021

Experts offer overview of COVID-19 breakthrough cases

A box of COVID-19 vaccine vials

Madison, Wis. – As the COVID-19 Delta variant continues to spread throughout the Unites States, there has been a lot of discussion about how the virus impacts vaccinated and unvaccinated people.

A breakthrough COVID-19 infection is defined as the detection of the virus – its RNA or antigen – in a saliva test or nasal swab collected from a person who is fully vaccinated, meaning they completed all recommended doses of a COVID-19 vaccine more than 14 days prior to detection, per the Centers for Disease Control and Prevention.

Breakthrough cases are possible, and experts expect to see them in this anti-viral strategy, according to Dr. Joseph A. McBride, assistant professor of adult and pediatric infectious disease at UW School of Medicine and Public Health.

However, vaccination remains the most effective and safe tool to protect ourselves against the virus, he said.

What makes the vaccine such a strong defense against the virus is how well it protects a person from being hospitalized or dying from a COVID-19 infection, and the data reflect that, according to McBride.

In July, the rate of infection in Wisconsin for unvaccinated people was 369.2 cases per 100,000 compared to just 125.4 cases in fully vaccinated people, according to the most recent available data from the state Department of Health Services.

The difference in the rate of hospitalization and death was even more stark as 18.2 per 100,000 people who were unvaccinated were hospitalized, and 1.1 per 100,000 died. Only 4.9 per 100,000 vaccinated people were hospitalized, and only .1 per 100,000 deaths due to COVID-19 were reported. As of Aug. 31, more than 173 million people in the U.S. have been fully vaccinated, and 12,908 people have been hospitalized or died, according to CDC data from 49 states and territories.

In other terms, unvaccinated people in Wisconsin are 32 times more likely than vaccinated individuals to be hospitalized, and they have a 13 times greater chance of death, according to an August New York Times report of national COVID-19 data.

“The goal of the vaccines is to safely provide protection to both the individual and to the general population, and the vaccines are meeting this goal,” McBride said. “Breakthrough infections are certainly possible but generally they are rarer and milder compared to COVID-19 infections in the unvaccinated.”