What Is a COVID Breakthrough Case? Dancing With the Stars Judge Derek Hough Tests Positive

Derek Hough, a U.S. professional dancer and Dancing With the Stars judge, has announced that he has a breakthrough case of COVID-19.

The media personality said in an Instagram post released on Tuesday: "Even though I've been fully vaccinated, I've just been diagnosed with a breakthrough case of COVID."

Hough said he was "feeling strong" despite his case, but he also announced that some upcoming dates of his Las Vegas dancing performance show would be rescheduled.

A COVID breakthrough infection is a case in which someone gets ill with the virus despite having already been fully-vaccinated.

It is important to note that breakthrough cases are not a sign that vaccines do not work. Vaccines help prevent infection and are highly effective at preventing severe COVID-related illness.

But vaccines are not 100 percent effective at stopping people from getting COVID. The U.S. Centers for Disease Control and Prevention (CDC) acknowledges that COVID breakthrough cases are expected, and that people who do experience a breakthrough case may spread COVID to other people.

However, fully-vaccinated people with a COVID breakthrough case are less likely to develop serious illness than an unvaccinated person.

People may notice that as the pandemic progresses, breakthrough cases of COVID become more common.

"As vaccinated individuals are more numerous, the numbers of breakthrough infections will also rise," Paul Wilmes, professor of systems ecology at the University of Luxembourg told Newsweek. "This paradox is linked to the fact that the available vaccines do not offer 100 percent protection against infection."

Andrew Brouwer, an assistant research scientist at the University of Michigan School of Public Health, told Newsweek: "With high community transmission, breakthrough cases will happen. But, breakthrough infections in vaccinated people are more likely to be mild and less likely to result in hospitalization or death."

Breakthrough COVID cases are also linked to suggestions that vaccine protection wanes over time. One study, published in the journal Nature on November 4, looked at the Pfizer vaccine and found that the risk of a breakthrough infection appeared to be higher in people who were vaccinated early than those who were vaccinated later.

However, the study results were preliminary and the reduction in effectiveness was observed against the Delta variant, and not other types of COVID.

The authors said future studies should look at different strains, as well as evaluating the protective effect of booster dose.

According to the CDC, 58.9 percent of the total U.S. population had been fully vaccinated as of November 16, amounting to a total of 195.4 million people.