UNC Health Talk

‘Breakthrough Cases’ Are Expected, and Boosters Can Help

When you look at the scientific data—and our country’s lived reality—there is no debate: COVID-19 vaccines work.

The overwhelming majority of people who have been hospitalized with or died from COVID-19 over the past few months, since vaccines became widely available, were unvaccinated.

That’s why it’s so important for people who are eligible for a booster shot, notably those 65 and older, to get one. A supplemental shot for at-risk populations will continue to protect against hospitalization and death.

“Your body’s immunity to many viruses, whether acquired naturally or through a vaccine, declines over time,” says UNC Health infectious diseases specialist David A. Wohl, MD. “A booster shot is an additional dose of a vaccine that gives a ‘boost’ to your immunity and provides better protection from disease. With a booster, the immunity that has already been established by a vaccine or through prior infection is stimulated again. So, in a way, the booster serves as a reminder to the immune system’s memory, which can fade over time.”

Why Do Vaccinated People Get COVID-19?

You’ve likely heard about “breakthrough infections,” when someone who is fully vaccinated gets the virus. While breakthrough infections garner a lot of attention, they’re expected.

Here’s why: While the COVID-19 vaccines are very good, no vaccine is perfect. Some people will get infected and some of these people may get sick even though they got the shot. The goal of a vaccine is not to eliminate all infections but to minimize severe illness, and in that regard, the COVID-19 vaccines are a huge success.

“First thing to understand is that the risk of even getting infected is reduced by vaccination. Among those who do get infected despite being fully vaccinated, there is not only a reduced risk of progressing to severe COVID-19 but also a short time that the virus can be found in the nose or throat—meaning a lower likelihood to spread the infection to others,” Dr. Wohl says.

Statistics from the Centers for Disease Control and Prevention (CDC) bear this out: Since the delta variant became dominant in the United States, unvaccinated people have been about 10 times more likely to be hospitalized or die than people who have been fully vaccinated. Studies from across the country also continue to show hardly any change in the protection against severe illness provided by the three COVID-19 vaccines, even as the protection against infection has slipped due to the delta variant.

Boosters Protect the Vaccinated

Most of the fully vaccinated people who have been hospitalized with or died from COVID-19 were ages 65 and older, according to CDC statistics. This is unfortunate, but not completely unexpected as older people may not make as strong a response to vaccines as those who are younger. The same is true for those with weaker immune systems. While there has not been evidence of a drop in protection provided by the vaccines against severe illness in the United States, the concern for waning immunity along with data showing a bump in antibody levels in those with a booster shot has led the CDC to recommend a booster for certain people.

If you’re eligible for a booster shot, get one. People who are eligible include:

  • Those who initially received two doses of either the Pfizer or Moderna vaccines at least one month ago and are moderately to severely immunocompromised. Pfizer recipients must be age 12 or older, and Moderna recipients must be 18 or older.
  • Those who initially received the two doses of the Pfizer vaccine at least six months ago and meet one of the following criteria:
  • Age 65 or older
  • Age 18 or older and have an underlying health condition that increases risk, such as cancer or chronic kidney disease
  • Age 18 or older and live or work in high-risk settings, including health care, schools, nursing care facilities and grocery stores

Right now, people who initially received the Johnson & Johnson vaccine are not yet eligible for a booster. There are study data expected shortly that will help the Food and Drug Administration (FDA) determine how best to boost people who received this vaccine. Similarly, for those who initially were vaccinated with Moderna and are not immunocompromised, a booster dose has not been authorized by the FDA but may be soon.

Receiving a booster when you’re eligible is the best way to make sure the vaccine continues to work its best for you.


Visit unchealthcare.org/vaccine for the latest information on the COVID-19 vaccines.