More than 63 million people have been fully vaccinated against COVID-19—an exciting step toward ending the pandemic after more than a year of lockdowns and mask wearing. Recently, the U.S. hit a new record by administering more than 4 million doses in 24 hours. President Joe Biden also confirmed that a majority of U.S. adults will be eligible for the vaccine by April 19, well before his initial May 1 deadline.
Clinical trials have shown that the the authorized coronavirus vaccines are safe and highly effective at preventing severe forms of COVID-19. But there’s still one question that researchers are in the process of answering: How long does vaccine protection actually last? And will follow-up doses be necessary to extend immunity and ward off new, more infectious variants of the virus?
Data continues to evolve, but it looks promising. Here’s what experts know so far.
What do we know about how long COVID-19 vaccine immunity lasts?
On April 1, Pfizer announced that its vaccine offers up to six months of strong protection against symptomatic COVID-19. Specifically, data from its phase 3 trial showed that the vaccine was 91.3% effective at preventing COVID-19 for up to six months after the second dose and 100% effective against severe disease as defined by the CDC.
Moderna’s vaccine offers similar protection so far, according to a letter published in The New England Journal of Medicine on April 6. Researchers found that “antibody activity remained high” through six months after the second dose in all age groups.
Richard Watkins, M.D., an infectious disease specialist and professor of internal medicine at the Northeast Ohio Medical University, says they have similar results because these vaccines both use mRNA technology, and therefore elicit an immune response in the same way.
At this point, “six months is the time frame for which they have secure information,” explains William Schaffner, M.D., an infectious disease specialist and professor at the Vanderbilt University School of Medicine.
But that doesn’t mean that the vaccines are only good for six months. It’s likely that the Pfizer and Moderna vaccines, and others like them, will provide immunity for longer than that, says infectious disease expert Amesh A. Adalja, M.D., senior scholar at the Johns Hopkins Center for Health Security. He bases his prediction from what we know about the flu vaccine, which is good for at least a year.
As for Johnson & Johnson’s vaccine, it was authorized by the Food and Drug Administration two months after the mRNA vaccines, so there’s currently less data to work with. This single-dose vaccine uses a different method of action—it’s a traditional adenovirus vaccine, like the flu vaccine—but it should also offer similar immunity, notes Dr. Schaffner. Why? The outcome—antibodies to SARS-CoV-2—is the same with both types of vaccines, he says.
What will happen when protection from COVID-19 vaccination wears off?
It’s not entirely clear right now, but Dr. Schaffner says “it won’t be like an on and off switch.” If protection from the vaccine wears off, it will fade slowly, he says. Because every person’s immune system is slightly different, it may happen at a different pace for each individual.
The good news is, doctors believe that if vaccinated people end up contracting COVID-19 down the road, their symptoms will certainly be less severe. “There should be some residual protection for quite some time,” Dr. Schaffner says. Basically, it’s expected that your immune system will at least remember that it’s seen something that looks like this coronavirus before and then go to work.
A small study published in January found that 95% of people who contracted COVID-19 still had antibodies to the virus up to eight months after they were infected—and experts predict that protection from the vaccine will last longer than natural immunity (a.k.a. becoming ill with COVID-19 and recovering). Not only that, Dr. Schaffner believes “protection from the vaccine will likely be more complete and offer more protection against variants than natural immunity.” More research is needed to prove that theory, though.
Will booster doses of the COVID-19 vaccine be necessary?
Currently, both Pfizer and Moderna are studying whether a booster shot may be helpful in maintaining COVID-19 protection following initial vaccination, especially when it comes to newly-emerging variants.
“It’s too early to determine whether or not booster doses may be needed and what the interval may be,” Dr. Adalja says, but there’s a good chance follow-up shots will be necessary, especially since there is a rare but real chance of having a breakthrough infection. This occurs when someone who is fully immunized against the virus still ends up being infected by it.
“These vaccines that we’re using are fabulous but they’re not perfect,” Dr. Schaffner says. While they are incredibly effective at preventing serious disease, there is still a slim chance for a minor COVID-19 illness to occur after vaccination.
“I would think we would need boostering at some point, whether it’s annually or every two or five years,” says Dr. Schaffner. “This virus will likely be with us for a long time, the way influenza is, and there will be variants and mutations that would require a booster to target them.”
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