Booster Recommendations After J&J/Janssen COVID Vaccine

Right now, there's no J&J/Janssen booster, and health experts advise people who initially had a J&J/Janssen COVID-19 vaccination to get a Pfizer-BioNTech or Moderna booster.

By September 2022, more than 17 million people in the US have received the Johnson & Johnson /Janssen (J&J) COVID-19 vaccine, a single-dose vaccine, according to the Centers for Disease Control and Prevention (CDC).

The three other COVID-19 vaccines approved in the US—the Pfizer/BioNTech and Moderna mRNA vaccines, and the Novavax protein subunit vaccine, require two jabs to be fully vaccinated.

Design by Jo Imperio

As the booster shots began to roll out, infectious disease experts considered whether recipients of the J&J/Janssen vaccine needed to have a booster.

Boosters have been recommended to help maintain immunity and to stave off emerging strains of the coronavirus. For example, the Delta variant accounted for 83% of sequenced cases in the US at one point, per CDC data. That variant and others that followed weren't around when the vaccines were first developed. As other strains have emerged, experts have raised concerns about how protective early forms of the vaccine could be.

In the US, public health officials have recommended booster shots for people who have had initial vaccination with Pfizer-BioNTech, Moderna, J&J/Janssen, and Novavax. But the only boosters available in the US are Pfizer-BioNTech and Moderna, according to the CDC.

So how would you go about getting another dose? Here's what we know so far, according to doctors and researchers.

What Is the J&J/Janssen Vaccine?

The J&J/Janssen vaccine uses a viral vector to deliver genetic material, according to the CDC. A vector is a delivery system. In this case, a virus is the delivery system for material that provides immunity against SARS-CoV-2, the virus that causes COVID-19.

The virus in the J&J/Janssen vaccine is modified in a way that makes it harmless. And it's also modified with a gene that codes for certain harmless portions of the SARS-CoV-2 virus. That triggers the body's immune system to be able to recognize and fight the COVID-19 virus if you encounter it later.

According to the CDC, the Pfizer-BioNTech and Moderna vaccines are recommended over the J&J/Janssen vaccine because the J&J/Janssen vaccine is less effective and has more side effects. However, the agency suggests that, while it has some drawbacks, the J&J/Janssen vaccine could be an alternative for people who have had an adverse reaction to one of the other vaccines or who don't have access to the other vaccines.

J&J Vaccine Protection

The 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 is no different. The CDC monitors variants circulating in the US.

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

A small study published in 2022 in Frontiers in Immunology found that J&J/Janssen's one-dose vaccine falls short. The research was based on blood samples from 17 people immunized with two doses of an mRNA vaccine and 10 people with one dose of J&J/Janssen. The researchers found that J&J/Janssen's vaccine started out with a lower rate of efficacy and showed a bigger drop against the Delta and Lambda variants.

"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 Ph.D., a virologist at New York University's Grossman School of Medicine, told The New York Times.

The findings counter other data suggesting that the single-dose vaccine generates a strong and persistent antibody response against the Delta variant. In a news release issued in July 2021, J&J cited data from a pair of small studies demonstrating the single shot's durable protection against multiple variants.

AstraZeneca Vaccine

The approved vaccines don't all work in the same way. While the Pfizer-BioNTech and Moderna vaccines are mRNA vaccines, another vaccine from AstraZeneca, which is not an option in the US, uses technology similar to the J&J/Janssen vaccine.

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, told Health. And because of that similarity, some information about the effectiveness of the AstraZeneca vaccine has been considered potentially helpful in assessing the J&J/Janssen vaccine.

One study published in 2021 in the New England Journal of Medicine involved Pfizer's mRNA vaccine and AstraZeneca's viral vector vaccine. Pfizer's vaccine was 88% effective against symptomatic disease from the Delta variant, versus 66% after two doses of AstraZeneca.

"What we're seeing with the AstraZeneca vaccine is that two doses of it are really required to provide you with optimal protection against hospitalization from the Delta variant," Dr. Gupta said. "Two doses really bumps you up into that 90% range," added Dr. Gupta.

What's more, study results out of the UK, published in 2021 in The Lancet, 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. "We're noticing that the levels of protection are equivalent to as though you got two doses of the mRNA vaccine," Dr. Gupta said.

Even before the CDC and Word Health Organization made formal recommendations about boosters for people who had the J&J/Janssen vaccine, infectious disease experts and critical care experts favored a second dose. Dr. Gupta is one of them. Here's what he said about the subject on Twitter:

Boosters After the J&J/Janssen Vaccine

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 explained. "What we're seeing," said Dr. Gupta, is that "two doses are really required to provide you with optimal protection against hospitalization from the Delta variant."

The CDC endorses a mix-and-match approach if you've had an initial dose of the J&J/Janssen vaccine. Furthermore, the agency does not discourage mixing and matching boosters after initial vaccination with any of the other brands. And the World Health Organization (WHO) also recommends that people who initially were vaccinated with the J&J/Janssen vaccine receive another brand's booster.

The Advisory Committee on Immunization Practices (ACIP), which guides CDC decisions, is "evidence-based," not "seat of the pants," so any decision about boosters would consider all of the data, said William Schaffner, MD, professor of infectious diseases at Vanderbilt University Medical Center in Nashville.

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," said Dr. Schaffner, "because the more of us that are vaccinated, the less the Delta variant can spread," Dr. Schaffner explained.

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 CDC, WHO, and their local public health department as resources.

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