Experts Predict When And How Often We'll Need COVID-19 Vaccine Boosters

Will we need coronavirus vaccinations every year? How will variants affect immunity and new shots? Here's what we know.
Experts increasingly believe COVID-19 booster shots will be necessary — but when is not yet clear.
Experts increasingly believe COVID-19 booster shots will be necessary — but when is not yet clear.

After an incredibly fast push to develop vaccines, followed up by a rocky initial rollout, the COVID-19 pandemic in the United States is at a hopeful point. Vaccination rates are climbing, while cases and deaths have dropped to their lowest point in nearly a year. The Pfizer, Moderna and Johnson & Johnson COVID-19 vaccines are working — and not just against the initial strain of the virus. The vaccines are holding up well against emerging variants so far.

But whether those rates will remain low, and whether we are truly inching toward a return to long-term normalcy, is not yet clear. And one possible determining factor is whether Americans are going to have to roll up their sleeves for another COVID-19 shot — or shots — and when.

Will we need to get one regularly, like a flu shot? What will the rollout process for boosters look like in the next year? Here’s what we know so far:

We don’t know how long immunity lasts — and that determines when we need COVID-19 vaccine boosters.

Many experts now believe that immunity against COVID-19 is going to wane with time, but no one really knows when. Nor do researchers know exactly how much a person’s immune response has to dip in order for the vaccines to stop doing their job. So far, research shows the Pfizer and Moderna vaccines offer robust immunity for at least six months, but what happens beyond then isn’t clear yet.

“We’ve had to very openly say from the get-go that we do not know what the durability of the mRNA vaccines or the J&J vaccines are,” Cameron Wolfe, an associate professor of medicine specializing in infectious diseases with Duke University’s School of Medicine, told HuffPost. “We knew great safety data. We knew great efficacy data. We did not know great durability data, because they haven’t been around for that long.”

Experts can try and answer that question in a few ways. The first is to use models to try and formulate a best guess.

“You can project how long it’s going to last by seeing a number of different time points and seeing how much antibody levels — or T-cell function, how good your immune system is at its broadest capacity — how long that lasts,” Wolfe said. “So if I know what it is at baseline ― if I know what it is after you’ve finished the vaccine course, and I know what it is at, say, three and six months ― then I can see how much decline may have taken place and extrapolate that.”

Then there is also real-time data collection. Wolfe, who was a volunteer in the early Phase 3 clinical trials for the Pfizer shot, and others like him continue to enter their results each week, saying whether they’ve developed COVID-19 or not.

“We can then model against those who took a placebo how long it’s expected to last for,” Wolfe explained. “That’s real, hard case data.”

Many experts believe boosters will be necessary soon, but some disagree with that assessment.

If immunity does wane over time, then subsequent COVID-19 shots will be necessary. But experts disagree over when that will take place.

The Centers for Disease Control and Prevention has indicated the agency is planning a year-plus ahead, although the agency doesn’t know for sure if and when any additional shots might be needed.

“What happens if, in a year from now, or 18 months from now, your immunity wanes? That’s really our job is to hope for the best and plan for what might happen if we need further boosters in the future, the way we get flu vaccine boosters every year,” CDC director Rochelle Walensky recently told CNBC.

Wolfe said he’d “be very surprised if it was in 2021. Beyond that, I’d be surprised if it wasn’t in 2022.”

How frequently boosters will be needed after that is also still up in the air. It could be that annual COVID-19 shots become the norm, in much the same way that annual flu shots are recommended.

However, there are experts who do not believe boosters will be necessary at all in the near feature. This is based on the fact that people who got immunized during the initial clinical trials have now been immunized for about 10 months — and they’re doing really well.

“We are not seeing breakthrough infections, even in the setting of surges,” Monica Gandhi, an infectious disease specialist with the University of California San Francisco, told ABC7, arguing that “we may not need booster shots.”

Anthony Fauci, the nation’s top infectious disease expert, acknowledges there’s a chance of this as well, recently telling NBC News that boosters aren’t necessarily a given.

“The bottom line is, we don’t know if or when we will need booster shots,” he said. “But it would be foolish not to prepare for the eventuality that we might need it.”

Variants are a significant factor in all of this.

Emerging variants and their impact on efficacy may just be what determines if subsequent COVID-19 shots are necessary, Wolfe said. That’s because if variants emerge that are able to dodge our current vaccines, people may need a reformulated shot that does a better job of targeting them.

Moderna, for example, is doing preliminary trials to figure out how a booster developed specifically to fight against the COVID-19 variant found in South Africa works against that strain. The company is also monitoring how a booster might work against the strain that emerged from Brazil. Pfizer and Johnson & Johnson are also conducting various booster trials.

The companies are also investigating whether a booster shot of the same formula will do the trick, or if their current vaccines need to be tweaked to better take on the variants. Additionally, the National Institute of Allergy and Infectious Diseases is planning studies to look at what happens if people mix-and-match vaccines — if boosters are, indeed, necessary. For example: Would it be possible for someone who received the Johnson & Johnson shot initially to get a Moderna booster?

And those are just some of the questions that linger about COVID-19 variants what they mean for our collective immunization efforts — and for the pandemic as a whole.

“We know increasingly reassuring information about durability, but the variant question remains open — and a little ominous, I think, as you see what’s happened across the subcontinent, and how we’re getting a rise here in the United States of the Brazilian variant,” Wolfe said.

All of which points to the pressing need to get as many people around the world vaccinated as soon as possible in order to stop the virus from spreading and evolving as it does.

The vaccine manufacturers also play a role.

“Pharmaceutical logistics and how they need to study a new booster, how they need to go into production and whether it’s efficient for them to try and combine those with alternative vaccines” will all play a role in the timing of potential COVID-19 boosters, Wolfe said.

The CEO of Pfizer announced recently that the company was testing whether a booster dose for its vaccine could be combined with a vaccine given to prevent pneumococcal disease.

“Those are company decisions as much as they are medical ones, but they factor in,” Wolfe said.

If a subsequent shot (or shots) are necessary, the process should hopefully be smoother than the initial vaccine rollout was. Some scientists have argued that any adjusted vaccines should not have to go through the same level of scrutiny that the initial vaccines were subject to, in much the same way that a new flu vaccine is updated annually without a long approval process.

But while planning and thinking ahead is important, experts say it is even more critical to focus on the here and now.

“Frankly,” Wolfe said, “we need to understand how to better vaccinate our current population.”

Experts are still learning about COVID-19. The information in this story is what was known or available as of publication, but guidance can change as scientists discover more about the virus. Please check the Centers for Disease Control and Prevention for the most updated recommendations.