You Might Need a Third Dose of the COVID-19 Vaccine

There has been some speculation that the mRNA COVID-19 vaccines (read: Pfizer-BioNTech and Moderna) may need more than the two doses to offer protection over time. And now, the CEO of Pfizer is confirming that it's definitely possible.

In a new interview with CNBC, Pfizer CEO Albert Bourla said that it's "likely" people who have been fully vaccinated with the Pfizer-BioNTech COVID-19 vaccine will need another dose within 12 months.

"It is extremely important to suppress the pool of people that can be susceptible to the virus," he said in the interview. Bourla pointed out that scientists still don't know how long the vaccine protects against COVID-19 once someone has been fully vaccinated because not enough time has passed since the clinical trials began in2020.

In clinical trials, the Pfizer-BioNTech vaccine was more than 95 percent effective at protecting against symptomatic COVID-19 infections. But Pfizer shared in a press release earlier this month that its vaccine was more than 91 percent effective after six months based on clinical trial data. (

The trials are still ongoing, and Pfizer will need more time and data to figure out whether protection will last longer than six months.

Bourla started trending on Twitter soon after the interview ran, with people having mixed reactions. "People are so confused and annoyed about Pfizer CEO saying we will most likely need a third shot in 12 months... Have they never heard about the *annual* flu vaccine?," one wrote. "It looks like the Pfizer CEO is trying to make some more money by mentioning the need for a third shot," said another.

Johnson & Johnson CEO Alex Gorsky also said on CNBC in February that people may need to get his company's shot annually, like the flu shot. (Provided, of course, the company's vaccine is no longer "paused" by government agencies due to concerns about blood clots.)

"Unfortunately, as [COVID-19] spreads, it can also mutate," Gorsky said at the time. "Every time it mutates, it's almost like another click of the dial so to speak where we can see another variant, another mutation that can have an impact on its ability to fend off antibodies or to have a different kind of response not only to a therapeutic but also to a vaccine." (

But experts aren't shocked by the possibility of needing more vaccine doses. "It's important to prepare for a booster and study it," says infectious disease expert Amesh A. Adalja, M.D., senior scholar at the Johns Hopkins Center for Health Security. "We know that immunity wanes with other coronaviruses at about one year, so it would not be surprising to me."

If a third vaccine is, in fact, needed, it "will likely be designed to be effective against the variant strains or at least some of them," says Richard Watkins, M.D., an infectious disease specialist and a professor of internal medicine at the Northeast Ohio Medical University. And, if a third doses is needed for the Pfizer-BioNTech vaccine, it's likely the same will be true for the Moderna vaccine, given that they use similar mRNA technology, he says.

Despite Bourla's comments (and the low-level hysteria they've created), it's really too soon to know for sure if a third dose of the vaccine will become a reality, says Dr. Adalja. "I don't think there's enough data to pull the trigger," he says. "I would want to see data on reinfection in fully vaccinated people one year out — and that data hasn't been generated yet."

For now, the message is simple: Get vaccinated when you can, and maintain all those other healthy behaviors that have been emphasized since the beginning of COVID-19, including washing your hands (correctly), staying home if you feel sick, etc. We'll need to take this — just like everything during the pandemic — one step at a time.

The information in this story is accurate as of press time. As updates about coronavirus COVID-19 continue to evolve, it's possible that some information and recommendations in this story have changed since initial publication. We encourage you to check in regularly with resources such as the CDC, the WHO, and your local public health department for the most up-to-date data and recommendations.