No, booster shots are not an indication that a vaccine is ineffective

COVID-19 vaccine booster shots have been top of mind for many people across the U.S. as booster shot eligibility has continued to expand.

The recommendations for booster shots have influenced some people to believe that the original COVID-19 vaccines were ineffective. According to a Kaiser Family Foundation survey, 71% of unvaccinated Americans think the necessity of booster shots means the vaccines aren’t working.

THE QUESTION

Are the recommendations for booster shots an indication that a vaccine is ineffective?

THE SOURCES

• Dr. William Schaffner, professor of preventive medicine and infectious diseases at Vanderbilt University Medical Center
• Centers for Disease Control and Prevention (CDC)
• Food and Drug Administration (FDA)
• Study on Pfizer COVID-19 vaccine effectiveness
• Study on mixing and matching COVID-19 vaccines

THE ANSWER

No, recommendations for booster shots are not an indication that a vaccine is ineffective. Booster shots and revaccinations are common among vaccines, especially those for viruses that continually change.

WHAT WE FOUND

Dr. William Schaffner, a professor of preventive medicine and infectious diseases at Vanderbilt University Medical Center, says each vaccine is different. Some require a booster shot beyond the initial series. Others, like the measles (MMR) vaccine, don’t. 

“We give you two doses, initially,” Schaffner said of the MMR vaccine. “And once that’s done, you don’t have to think about It for the rest of your life.”

But booster shots are recommended for some vaccines because protection against those diseases wanes over time. Schaffner says that’s common for vaccines and not a sign that they are ineffective.

“The vaccines work just as well,” Schaffner said. “It’s just that you need a reminder.”

That reminder, Schaffner says, will lead to a robust response because the immune system has already been primed with the original vaccine series.

“That will result in a very rapid and very high rise in protection in antibody levels,” he said. “That’s a classic booster response.”

The Tdap vaccine, which vaccinates people against tetanus, diphtheria and pertussis, is an example of a vaccine that the CDC recommends booster shots for. The CDC says adults should get a Tdap vaccine booster every 10 years. It’s also recommended that women get a dose of the vaccine when pregnant.

There are other vaccines in which reimmunization is recommended, like the pneumococcal vaccine for certain at-risk individuals.

“You wane and then the vaccine will get you up to where you were before, but not any higher,” Schaffner explained. “So, we call that reimmunization rather than boost.”

There are also vaccines like the flu shot, which the CDC recommends annually because the virus keeps changing.

Schaffner said many vaccine experts expected booster shots would be recommended for the COVID-19 vaccines because “more often than not, that’s the way vaccines are.”

Multiple studies show the effectiveness of the COVID-19 vaccines can drop over time. The CDC evaluated those studies when it recommended booster shots for certain people, many of whom were among the first to get vaccinated when the rollout began in December 2020. 

A federal clinical trial, which has not yet been peer-reviewed, found antibody levels increased after people received booster shots. The FDA also says it reviewed studies that showed antibodies rose after booster shots of the Pfizer, Moderna and Johnson & Johnson COVID-19 vaccines.

Schaffner said that’s exactly what booster shots are for.

“[The vaccines] work for most people very well,” he said. “Sure, after a little bit of time, we're getting some waning. So, we'll just stimulate our immune system again, and we'll get a big antibody response.”

Data from the CDC as well as states across the U.S. show that people who are vaccinated are better protected against COVID-19 than people who are not.

More from VERIFY: Yes, you can now ‘mix and match’ the COVID-19 vaccine booster shots in the US