Right now, there's no government recommendation to get a second dose.

By Karen Pallarito
July 22, 2021
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More than 13 million people in the US have received the Johnson & Johnson (J&J)/Janssen COVID-19 vaccine, a single-dose, one-and-done regimen. The Pfizer/BioNTech and Moderna mRNA vaccines, by contrast, require two jabs to be fully vaccinated.

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Credit: Design by Jo Imperio

In recent weeks, some infectious disease experts have openly debated the question, Do I need an mRNA vaccine booster after a J&J shot? Those who favor the idea say an additional dose may help stave off emerging strains of the coronavirus. The new and highly transmissible Delta variant now accounts for 83% of sequenced cases in the US, per the latest CDC data. (Lambda, another variant, has not proliferated as Delta has.)

But public health officials have yet to recommend a booster.

So should you seek out an extra dose? And how would you go about getting one? Here's what we know so far, according to doctors and researchers.

Why are some experts talking about a booster for J&J vaccine recipients?

The current crop of COVID-19 vaccines cleared for use in the US were designed to protect against the original virus. But viruses have a knack for mutating, and SARS-CoV-2 (the one that causes COVID-19) is no different. The CDC is monitoring multiple variants circulating in the US, including Delta, which has been linked to more severe disease.

While there's good evidence that the two-dose mRNA vaccines are effective against the new variant, less is known about the J&J one-dose vaccine.

Now a small new study finds that J&J's one-dose vaccine falls short. The research, which has yet to undergo peer review, is based on blood samples from 17 people immunized with two doses of an mRNA vaccine and 10 people with one dose of J&J, the New York Times reported. J&J's vaccine started out with a lower rate of efficacy and showed a bigger drop against the Delta and Lambda variants, according to the Times.

"The message that we wanted to give was not that people shouldn't get the J&J vaccine, but we hope that in the future it will be boosted with either another dose of J&J or a boost with Pfizer or Moderna," study author Nathaniel Landau, a virologist at New York University's Grossman School of Medicine, told the Times.

The findings counter other data suggesting that the single-dose vaccine generates strong and persistent antibody response against the Delta variant. In a news release issued earlier this month, J&J cited data from a pair of small studies (again, not yet peer reviewed) demonstrating the single shot's durable protection against multiple variants.

Rapid spread of the Delta variant is raising concerns about vaccine protection against variants

In a matter of weeks, the Delta variant has swept across the nation and now represents the majority of cases. It's also on its way to becoming the dominant strain globally, the World Health Organization said on Wednesday. The rampant spread of Delta, along with simmering concerns about whether the one-dose J&J vaccine will hold up against the variant as well as the Pfizer and Moderna mRNA vaccines, has fueled the booster debate.

One recent study from Public Health England added to the discussion. The study involved Pfizer's mRNA vaccine and a "viral vector" vaccine from AstraZeneca (which is not an option in the US but uses technology similar to the J&J vaccine). Pfizer's vaccine was 88% effective against symptomatic disease from the Delta variant, versus 66% after two doses of AstraZeneca.

AstraZeneca is similar in many ways to J&J, Vin Gupta, MD, affiliate assistant professor of health metrics sciences at the University of Washington's Institute for Health Metrics and Evaluation in Seattle, tells Health. "What we're seeing with that vaccine is that two doses of it are really required to provide you with optimal protection against hospitalization from the Delta variant," he says. "Two doses really bumps you up into that 90% range."

What's more, early study results out of the UK suggested that a mix-and-match approach—one dose of AstraZeneca and one dose of an mRNA vaccine (in this case, Pfizer)—produced a better immune response than two AstraZeneca doses, Reuters reported.

"We're noticing that the levels of protection are equivalent to as though you got two doses of the mRNA vaccine," per Dr. Gupta.

It's important to point out that the US Centers for Disease Control and Prevention (CDC) at this time does not endorse a mix-and-match approach. Neither does the World Health Organization.

Still, some infectious disease and critical care experts favor a second dose. Dr. Gupta is one of them. Here's what he recently said on Twitter:

"I'm not the only voice saying this," he told Health in an interview last month."But if the goal here is to fully provide everybody the opportunity of the same level of protection as we enter an uncertain period with a really dangerous version of the virus, there's a risk in saying, well, we need to wait until we have our own randomized control trial."

Should J&J vaccine recipients get a second dose?

It's a question more people are asking, particularly those with weak immune systems who are concerned about contracting the Delta variant.

So what would be the benefit of adding a second dose of an mRNA vaccine when you've had the J&J vaccine? Your immune system gets the priming effect of the first dose and the boosting effect of the second dose, Dr. Gupta explains. "What we're seeing," he says, is that "two doses are really required to provide you with optimal protection against hospitalization from the Delta variant."

But in a recent joint statement on vaccine boosters, the CDC and US Food and Drug Administration (FDA) say fully vaccinated Americans "do not need a booster shot at this time," that they are protected from severe disease and death from COVID-19 and its variants. "Virtually all COVID-19 hospitalizations and deaths are among those who are unvaccinated," the agencies point out.

On Thursday, the Advisory Committee on Immunization Practices (ACIP), which advises the CDC on vaccine safety and effectiveness, reviewed emerging data on booster doses for immunocompromised individuals. The panel made no recommendation on giving this population a second or third dose. The FDA must first amend the J&J, Pfizer, and Moderna vaccines' emergency use authorization or allow ACIP to make an "off label" recommendation. For now, the plan is to continue reviewing the data.

ACIP decisions are "evidence-based," not "seat of the pants," so any decision about boosters would consider all of the data, says William Schaffner, MD, professor of infectious diseases at Vanderbilt University Medical Center in Nashville. "And remember," he says, "there are always two sides to the data: What's the potential benefit and what are the safety issues? Are you going to get more side effects of one kind or another?"

I've had the one-dose J&J vaccine. How would I even get a booster?

It's a good question, and the short answer, at the moment, is talk to your doctor.

Dial Hewlett Jr., MD, deputy commissioner of health and medical director in the Division of Disease Control at New York's Westchester County Department of Health, tells Health that decisions around booster shots may need to be more nuanced than a blanket recommendation for everyone who's had the J&J shot. Doctors may decide, for example, to administer a second dose to their immune-compromised patients who fail to mount a robust response to the initial dose.

"There's nothing to keep them from administering the vaccine to their particular patient, even though they've been fully vaccinated," Dr. Hewlett explains. But without recommendations from the ACIP, you get into a gray area, he points out. Would insurers even cover the cost of another dose if you're fully vaccinated?

While there are loopholes in the system, if you've already had the J&J shot, it could be difficult to line up an mRNA dose, depending on where you live, says Dr. Gupta. And that's assuming you're willing to pay for it out of pocket.

Amid the chatter about boosters, public health advocates and clinicians continue to drum home the importance of getting vaccinated in the first place.

"That will protect all of us," says Dr. Schaffner, "because the more of us that are vaccinated, the less the Delta variant can spread."

The information in this story is accurate as of press time. However, as the situation surrounding COVID-19 continues to evolve, it's possible that some data have changed since publication. While Health is trying to keep our stories as up-to-date as possible, we also encourage readers to stay informed on news and recommendations for their own communities by using the CDCWHO, and their local public health department as resources.

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