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What to know now if you received the J&J COVID-19 vaccine

There seems to be little guidance for recipients of the least-used vaccine. Here is the latest on the shot's safety, protection and boosters.
Covid-19 Vaccines Stock Pictures
The Johnson & Johnson COVID-19 vaccine became available in February of 2021.Artur Widak / NurPhoto via Getty Images
/ Source: TODAY

Almost 17 million Americans have received the Johnson & Johnson COVID-19 vaccine — equivalent to the populations of New York City, Los Angeles, Chicago and Philadelphia combined — a huge number that seems to have been forgotten in a country dominated by Pfizer or Moderna recipients.

The single J&J Janssen shot was initially touted for its convenience and accessibility — a one-and-done regimen that didn’t require ultra-cold storage.

But there were questions about its efficacy compared to the two-shot mRNA vaccine series and concern about the risk of rare blood clots. The Centers for Disease Control and Prevention now calls the Pfizer and Moderna vaccines the “preferred” options over J&J in most situations.

There seems to be little guidance now for recipients of the least-used vaccine. So if you’ve already gotten the J&J shot or are still considering it, what’s the latest on the protection it provides and whether you need more shots?

TODAY asked Dr. Daniel Kuritzkes, chief of the division of infectious diseases at Brigham and Women’s Hospital in Boston and professor of medicine at Harvard Medical School; and Dr. Roy Gulick, chief of the division of infectious diseases at NewYork-Presbyterian/Weill Cornell Medical Center and professor of medicine at Weill Cornell Medicine.

Are you still considered fully vaccinated with one J&J shot?

Yes, a person who has received a primary series of a COVID-19 vaccine — a single-dose, in the case of J&J’s vaccine — is considered fully vaccinated, according to the CDC.

“I think that’s in sore need of updating,” Kuritzkes said. “Practically speaking, based on the totality of the data, I would consider that a single shot of the J&J vaccine is inadequate to provide full protection.”

The CDC is now moving towards the terminology of staying “up to date” with your vaccines, which means additional shots.

What does it mean to be boosted if you’ve had the J&J vaccine?

It means receiving a booster dose at least two months after getting the initial shot. Booster doses from Pfizer or Moderna are preferred, the CDC said.

“For J&J, there is some data to suggest that antibody levels are better if you switch to the mRNA vaccine and in particular Moderna, so many people will opt for that choice to get higher antibody levels,” Gulick said.

You can also get a second J&J shot, which showed high levels of protection against the omicron variant, according to data published ahead of peer review in December.

People sometimes talk about being “triple vaxxed” in the context of mRNA vaccines — the two-shot series, plus a booster — which essentially translates to being “double vaxxed” for J&J recipients: the initial single dose of the vaccine, plus a booster.

Are people who received the J&J shot plus a booster equally protected as those vaccinated and boosted with mRNA shots?

“We don’t know the answer to that. These groups have not been compared,” Gulick said.

Kuritzkes agreed, noting scientists don’t have enough follow-up yet.

But he predicted that “if you had a J&J vaccine at some point during the spring or summer (of 2021) and then you got boosted in the fall with an mRNA vaccine, at this point it’s likely that you have very high antibody levels that would be the equivalent of somebody who was ‘triple vaxxed.’”

“Right now, optimal protection is with a third shot of an mRNA or a second shot of a J&J,” said Dr. Anthony S. Fauci on Tuesday.

Is there a need or benefit of J&J recipients to receive two shots of the mRNA vaccine?

Not in the context of getting the two-shot mRNA series 21 or 28 days apart, both experts said. That has not been studied and is not currently recommended, but there’s active research going on right now to see if people need a second booster, Gulick noted.

What do we know about J&J’s protection now?

The largest real-world study to date, sponsored by Johnson & Johnson, showed a single shot of the vaccine provided protection against COVID-19 breakthrough infections, hospitalizations and intensive care unit admissions for up to six months, the company announced Thursday.

Last year, it said a single dose of its vaccine offered 70% protection against moderate to severe forms of the disease, with a second shot given about two months after the first increasing the effectiveness to 94%.

Besides stimulating the immune system to produce antibodies, vaccines also induce T cells, another layer of protection.

“The major plus for the J&J vaccine is that it does induce very high levels of cytotoxic T cells. These are cells that are instructed to kill virus-infected cells,” Kuritzkes said.

The T cells are persisting whether or not antibody levels are decreasing, which may explain why J&J’s level of protection appeared to remain pretty stable at six months compared to the decline observed for the mRNA vaccines — though they still started off with a higher level of protection, he noted.

Studies continue on how durable and stable the protection of all the vaccines is.

If you had the J&J vaccine without any blood clot problems, is it OK to get the second shot?

It’s unclear, both experts said. The vaccine has been linked to the risk of rare but potentially life-threatening blood clots. At least 54 people in the U.S., mostly younger women, have been hospitalized from these blood clots, and nine people have died.

For those considering a J&J booster, the risk may linger even if they experienced no problems with the initial shot.

“Just because that didn’t happen the first time around, I’m not sure you could guarantee it wouldn’t happen the second time around,” Kuritzkes said.

“If you were an older person or a man and wanted to get a boost of J&J and you did fine with the first the shot, it’s probably fine. I would still have some hesitation if I were a young woman getting boosted with the J&J.”