The Slatest

Why You Might Want a Booster Shot if You Got the J&J Vaccine

There’s no federal guidance for them yet, but experts suggest asking your doctor anyway.

A syringe drawing J&J vaccine from a vial. The medical worker holding the vial is out of focus in the background.
Sander Koning/ANP/AFP via Getty Images

Earlier this week, Angela Rasmussen, a virologist at the University of Saskatchewan, got a booster shot of the coronavirus vaccine. Previously, she’d received a dose of the single-shot vaccine produced by Johnson & Johnson. But she was watching the delta variant spread in the U.K.—and knew a single-dose vaccine wasn’t as effective against the coronavirus as it could be. So she topped up her protection with a dose from Pfizer.

“I just decided that it was a good idea for me to get a boost,” she explained. “We know that at least two doses of an adenovirus vector vaccine and an mRNA vaccine provide protection equivalent to having two mRNA vaccines. So, it was really just to be safe, [and] protect the community around me.”

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On Tuesday, White House Chief Medical Adviser Anthony Fauci said the delta variant of COVID-19 is the “greatest threat” to national attempts to control the pandemic. A week prior, the Centers for Disease Control and Prevention declared the variant as being one of concern due to heightened transmissibility and more severe disease should someone contract that mutation of the virus.

Boosters for the COVID-19 vaccines may be necessary for everyone within the next year, according to the Food and Drug Administration’s director of biologics, Peter Marks. But some experts are arguing that recipients of the single-dose Johnson & Johnson should receive a booster in the form of a dose of Pfizer or Moderna—sooner rather than later.* While there’s no such guidance in the U.S., Canada already recommends it for recipients of the AstraZeneca vaccine. (Though Rasmussen originally got the J&J, she figured getting the mRNA was a fair extrapolation since J&J is also a viral vector vaccine.)

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To be clear, all of the three vaccines approved in the States, including the Johnson & Johnson vaccine, offer valuable protection against the coronavirus variants, including delta. Michael Lin, a professor of bioengineering and neurobiology at Stanford University, estimates that the efficacy of J&J against the delta variant is in the ballpark of 64 percent against symptomatic disease and 82 percent against severe disease. The effectiveness has not been studied directly; Lin points to the similarity of another variant—beta—that has. The J&J vaccine can also be compared to the AstraZeneca vaccine, which is based on the same adenovirus technology.*

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“With the delta variant, studies out of Britain show that one shot of either the [AstraZeneca] or an mRNA vaccine offers relatively low protection, and the second shot is critical,” explained Paul Sax, an infectious disease doctor, over email. “There are good data that an mRNA vaccine after the AZ vaccine boosts measurable responses—so boosting does appear to work,” he added.

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Some experts emphasize that the most important thing to do to protect against the delta variant is simply to get vaccinated. As infectious disease researcher Monica Gandhi explained on Slate’s What Next, “if we could get everyone the vaccine, we wouldn’t be in any situation where anyone had to die”—that is, from the delta variant or any variant of the coronavirus.* How well a vaccine is able to protect you is based not just on which vaccine you got, but also the overall vaccination rates in your area. “If you were in a community that has high overall vaccination and you have J&J, you really don’t have much to worry about because in that community, you will not only be protected by your J&J vaccine, you’ll be protected by the high level of vaccination in your entire community around you,” said Rasmussen. “And that’s what people really should think about before they start getting too worried about whether or not J&J protects against delta.”

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But a significant portion of Americans is not vaccinated. In this context, getting a booster to make yourself as safe as possible might just make sense. “If we can do better than 60 percent [efficacy] and we can do it at essentially zero cost, we should,” says Lin, noting that 60 percent protection would still mean that a large chunk of folks who are vaccinated with J&J would experience symptomatic COVID. “And it’ll give you a really good bang for buck if you could give a boost to those people who are 60 percent protected and bring them to 90 percent. That’s easily done with the RNA boosters since we have all these spare RNA doses sitting around.”

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Lin also stressed that any projections as to protection offered by J&J against the delta variant are, currently, just educated guesses. “We don’t know yet. And it seems that’s not an assumption you really want to rely on in terms of protecting against the worst-case scenario”—that is, a surge in cases driven by the delta variant.

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The CDC and the FDA have yet to issue advice on using an mRNA vaccine as a second shot for those who received J&J as their first dose. All the researchers and physicians who spoke with Slate emphasized the importance of speaking with a doctor before steering away from the recommended guidelines—even though they think a second shot would be beneficial themselves.

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“It’s very reasonable for people to worry about the effectiveness of the J&J vaccine with delta [becoming] the dominant variant, and to consider boosting,” wrote Sax via email. “It may not be at a sufficient level of evidence to change national guidelines, but it’s a conversation those who have received this vaccine can appropriately have with their doctors.”

On Twitter, Lin urged the CDC to go ahead and provide formal guidance on second doses for those who received the J&J vaccine to help prevent a surge from happening:

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National agencies only suggest a medical intervention once it has gone through clinical trials and have data proving its efficacy and safety, says Lin. “But in medicine we actually have more leeway beyond the prescribed indications”—that is, what a drug or shot is approved by regulators to do. “Your doctor can prescribe a drug to you for something that’s not on the label. It’s an off-label use. And it’s up to the medical judgment of the doctor to do this. We can do this with vaccines as well.”

Correction, June 25, 2021: This piece originally misstated that the AstraZeneca vaccine is a single-dose vaccine. It is typically given as part of a two-dose regimen. Also, due to an editing error, the piece originally misspelled Monica Gandhi’s last name.

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