How Are Some Vaccinated People Still Getting COVID-19? Here's What You Need to Know About "Breakthrough Cases"

This does *not* mean the vaccine isn't working, experts say.

Yes, all three approved COVID-19 vaccines are safe and highly effective. But no, they don't block the virus 100% of the time, which is how "breakthrough cases" occur.

Government officials—and citizens from coast to coast—are buzzing about these cases, especially amidst the rise in the delta variant and a few high-profile hospitalizations, including entertainment reporter Catt Sadler. So Anthony Fauci, M.D., the director of the U.S. National Institute of Allergy and Infectious Diseases, spoke before Congress earlier this week to answer questions and clear up some details.

"When you hear about a breakthrough infection, that doesn't necessarily mean the vaccine is failing," Dr. Fauci said. "I think people need to appreciate when you talk about breakthrough infections that the original data from the clinical trial—the efficacy data was based on preventing clinically apparent disease, not preventing infection, such as a symptomatic infection."

Sick woman sitting in bed with COVID-19 cells floating around her
Getty Images / staticnak1983 / pijama61

Remember the news around the time of the FDA review of the Moderna, Pfizer, and Johnson & Johnson vaccines that explained their "efficacy rate"? That statistic is basically another way to say how likely we are to acquire the virus even after being vaccinated. (This happens with every kind of vaccine, including the yearly flu shot—even if you receive it, there's a small chance you can still get infected.) As a refresher, here's the efficacy rate for each:

  • Pfizer-BioNTech: 95%
  • Moderna: 94.1%
  • Johnson & Johnson: 72% overall (and 86% effective in preventing severe cases)

Dr. Fauci confirmed last week (probably right around the slot he carved out to speak with Olivia Rodrigo at the White House) that the risk of a vaccinated person spreading COVID-19 to another person is far less than an unvaccinated person spreading the virus. Plus, nearly all breakthrough cases are either asymptomatic or mild.

So why is the total number of breakthrough infections rising? This is due to the greater pool of people who are vaccinated: 161.6 million Americans are fully vaccinated as of July 20. Since more of us fall into the vaccinated cohort than the unvaccinated cohort compared to weeks and months ago, there is a larger number of us who may report as a breakthrough case, rather than a "regular" case of COVID-19.

"As the number of infections in the U.S. increases, there may be a slight increase in the number of 'breakthrough' infections,'' Shobha Swaminathan, M.D., an associate professor and infectious disease expert at the Rutgers New Jersey Medical School, tells ABC News. "However, the majority of infections continue to be reported among those who have not been vaccinated."

Seeing that the delta variant now accounts for 83 percent of new COVID-19 cases in America, infectious disease experts say that this variant could be contributing to the rise in overall breakthrough cases. But regardless of what variant it is, and even with the highly-transmissible delta variant sweeping across the U.S., more than 99% of COVID-19 deaths are among people who are unvaccinated.

"Vaccine breakthrough cases occur in only a small percentage of vaccinated people. To date, no unexpected patterns have been identified in the case demographics or vaccine characteristics among people with reported vaccine breakthrough infections," the CDC clarifies. "COVID-19 vaccines are effective [and the] CDC recommends that everyone 12 years of age and older get a COVID-19 vaccine as soon as they can." The Pfizer-BioNTech vaccine is approved for children 12 years and older.

In addition to having much higher protection from the virus and scoring the peace of mind that comes from that fact, "people who have been fully vaccinated can resume activities that they did prior to the pandemic," the CDC adds.

The Bottom Line

As it goes with all vaccines, there remains a small chance of becoming infected with COVID-19 after receiving one of the three FDA-approved vaccines. The small percentage of vaccinated people who do test positive for COVID-19 are classified as "breakthrough cases" and nearly all cases are asymptomatic or mild. These "breakthrough cases" are to be expected and the CDC has not identified any alarming patterns with the cases.

As the infection rates increase across the U.S., in large part due to the highly-transmissible delta variant, we can expect to see a slight increase in breakthrough cases as well. It should be noted that 99% of COVID-related deaths are among those who are unvaccinated. To help prevent further transmission of the virus and additional deaths, the CDC recommends everyone 12 years of age and older get vaccinated.

The information in this story is accurate as of press time. However, as the situation surrounding COVID-19 continues to evolve, it's possible that some data have changed since publication. While EatingWell is trying to keep our stories as up-to-date as possible, we also encourage readers to stay informed on news and recommendations for their own communities by using the CDC, WHO, and their local public health department as resources.

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