Generally, a booster shot is administered at some point after initial vaccinations in order to further bolster immunity, to reignite immunity after it has waned, or to protect against new strains of a virus for which someone has already been inoculated. Depending on the reason a booster is needed for continued protection against COVID-19, the shot might be identical to the vaccines already administered or slightly tweaked to add specific protection against virus mutations.
Why you'll need a COVID-19 vaccine booster shot
It's unclear if we will actually need a booster for the COVID-19 vaccines. Potential timing for them, then, is even less clear. Uğur Şahin, co-founder and CEO of BioNTech, the makers of the Pfizer COVID-19 vaccine, says that booster shots are a necessity. "At the end of the day, it really matters that we get this pandemic under control. And we will not get it under control without boosting. That’s my strong opinion,” Şahin said during a panel session at the STAT Breakthrough Science Summit. However, officials from the Centers for Disease Control (CDC) and the Food and Drug Administration (FDA) aren't convinced, and say we potentially need several more months of data before knowing if a booster shot is necessary.
"A booster is going to depend on two factors," says Timothy Brewer, MD, professor of medicine and epidemiology at UCLA. One, he explains, is whether or not COVID-19 immunity diminishes over time. "We know it does, but the question is how much," Dr. Brewer says. So far, we've seen evidence that immunity lasts as far out as eight months, but we have no data beyond that yet.
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The second variable, or impetus for a booster, is virus mutations. The reason you get a flu shot every year, Dr. Brewer explains, isn't because your immunity from last year's flu shot wore off but rather that the virus has changed enough so that last year's shot no longer offers adequate protection from it. Fortunately, he says, coronaviruses don't change as rapidly as influenza viruses. "While they certainly do change—that's why we have variants—the question is, do they change rapidly enough that you need to get a booster, and that's still unclear," says Dr. Brewer.
Existing variants—specifically, the Delta B.1.617 variant, the South African B.1351 variant, the Brazilian P.1 variant, and the two Californian B.1.427 and B.1.429 variants—render current vaccines somewhat less effective, to varying degrees. So while existing vaccines still prevent serious disease, hospitalization, and death in those infected by these strains, they don't necessarily protect as well against these infections, full-stop. "A study out of Israel suggests that the South African variant infections may occur even in people who received the Pfizer vaccine," says Dr. Brewer. It's possible, then—based on these early findings—that we'll need boosters specifically to help protect against these strains. But Dr. Brewer says this isn't known for certain yet.
When you'll need a COVID-19 vaccine booster shot
Drug companies are proactively preparing booster shots to roll out in late 2021 or early 2022. Pfizer's CEO Albert Bourla recently said it's "likely" people will need a booster within the next 12 months, and Moderna has announced that its booster will be ready by the fall. Just what those boosters will look like—how and why they will differ from the initial doses received—remains to be determined as the companies test out various options and await data.
But the decision as to whether or not populations need to be reinoculated with a booster shot isn't the drug companies' to make, says Anthony Fauci, MD, director of the National Institute of Allergy and Infectious Diseases (NIAID) and the chief medical advisor to President Joe Biden. That call will instead come from the CDC. Dr. Fauci currently projects that experts will know enough by the end of this summer or the start of fall to make a determination regarding the need for boosters.
In short, it's unknown as of yet whether or not you'll need a booster at all, let alone the exact timing of said booster. Data is still being collected in real-time, as it has been throughout the pandemic. And while such unknowns can be frustrating or even scary, keep in mind that if you've been vaccinated, you are currently well protected from serious illness and likely will be long enough for the booster question to be answered.
If we do need them, the relative success of our current vaccination program bodes well for boosters, too. Last week, Andy Slavitt, senior advisor to President Biden’s COVID response team, told reporters that the administration is considering the potential need for boosters in its planning efforts. “Requiring additional shots in the future is obviously a foreseeable potential event,” he said. "I can assure you that when we do our planning, when the president orders purchases of additional vaccines as he has done, and when we focus on all the production expansion opportunities that we talk about in here, we very much have scenarios like that in mind."
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