People who are fully vaccinated against COVID-19 can still test positive for the virus. Health officials have come to refer to that as a “breakthrough case” of the disease.
But some health experts say the term can be misleading and misconstrued, especially as new variants have emerged and vaccination rates across the country have slowed.
“I think it was setting the vaccine up for an impossible standard that vaccines can’t possibly meet,” said Jennifer Nuzzo, a senior scholar at the Johns Hopkins Center for Health Security and the lead epidemiologist for the Johns Hopkins COVID-19 Testing Insights Initiative.
COVID-19 vaccines were first approved in mid-December of 2021 and are now available to children 5 and older. Two of the vaccines, one manufactured by Pfizer-BioNTech and the other by Moderna, have since been granted full approval by the Food and Drug Administration.
Researchers have established that all available COVID-19 shots offer significant protection against severe illness and death. According to data from the state health department, unvaccinated Texans are 16 times more likely to die from a COVID-19-related illness compared to fully vaccinated individuals.
The state health department doesn’t include breakthrough cases on its COVID-19 dashboard. In Dallas County, 27,943 breakthrough infections have been reported out of 549,239 total COVID-19 cases as of Feb. 3. That’s only about 5% of all cases.
Nuzzo, who spoke last month at a webinar, said the term “breakthrough” may give people a false impression about the function of the shot.
“They’re not forcefields,” she said. “They don’t repel the virus from your body.”
Here’s what health experts said you need to know about the term “breakthrough case” and COVID-19 shots.
Cells have to be infected for the vaccine to respond
The scientific definition of infection means that a person must encounter a disease for a vaccine to respond, Nuzzo said.
“What vaccines do is train your immune system to recognize the virus and then to react quickly, hopefully before you have any symptomatic disease, but certainly before too many of your cells become infected by the virus,” she said. “And how does your body know that the virus is there?
“Usually it’s when the virus invades your cells, which is the technical definition of infection.”
The goal of a vaccine isn’t to eliminate all infections
Ultimately, a successful vaccine shouldn’t be viewed as one that eliminates infection, but one that significantly reduces hospitalizations and death, Nuzzo said.
“I view any infection [in a vaccinated person] that doesn’t send somebody to the hospital as a success,” Nuzzo said. “If this virus could never put people in the hospital or kill them, most people would have never heard of it. Losing sight of that is fueling a level of anxiety that I think is just unhelpful but also underselling the vaccines.”
Dr. Hana El Sahly, a professor of molecular virology and microbiology and infectious diseases at Baylor College of Medicine in Houston, said it’s important to remember the standard that was initially set by the World Health Organization for what a successful COVID-19 vaccine would look like.
“What we would have called a successful vaccine is if it prevented 50% of documented infections, as long as it had a role in preventing severe disease,” she said. “Once these vaccines rolled into the communities … the vaccines maintained real high efficacy against death and against ICU admissions and the need for being on ventilators.”
More COVID-19 cases means more breakthrough infections
As vaccination rates have slowed over the course of the pandemic, some health experts are concerned that the impression that some people may get from the term “breakthrough case” plays into skepticism and anti-vaccination ideals.
Health experts say people should remember that “breakthrough cases,” or getting infected with a disease that you are vaccinated against, are common and expected with any shot.
“There’s not a single vaccine that’s a hundred percent,” said Dr. Grant Fowler, family medicine department chair at TCU School of Medicine in Fort Worth and chairman of the family medicine department at JPS Health Network. “But our whole goal is to [minimize] it in the population and protect the vulnerable.”
Nuzzo said it’s also important to remember that widespread testing for COVID-19 also means a larger share of breakthrough cases are being detected.
The Centers for Disease Control and Prevention has noted that if there are more COVID-19 cases occurring, like during the recent omicron surge, more breakthrough cases will naturally be detected.
“We often hold up the measles vaccine as the standard of the best vaccine,” Nuzzo said. “But if we had a lot of measles circulating, and if we did a lot of testing, we would see a lot more breakthrough infections that we just don’t notice because the symptoms are so mild.”
Other terms for “breakthrough”
While the impression a person gets from the term breakthrough case is “in the eye of the beholder,” Sahly said, it’s probably better for health care professionals to use a different term or phrasing when talking to patients.
“In the mind of the common person, it may be wise to stop using the word ‘breakthrough’ because it comes with the implication that something wrong has happened, when nothing wrong really has happened,” she said.
Sahly says she tries to use different language when not speaking with someone in the scientific community.
‘If I’m talking to the lay person, I try to use the word ‘have gotten two doses of vaccine and an infection,’ or ‘two doses of vaccine and COVID,’ depending on the situation,” Sahly said.
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