An Epidemiologist Explains What We Know About Johnson & Johnson Booster Shots So Far

Photo: Getty Images/ Andriy Onufriyenko
This week, the Biden Administration announced that people in the United States who received two doses of either the Moderna or Pfizer-BioNTech COVID-19 vaccines would be eligible for a third dose beginning eight months from the date of their second shot. Those additional doses are set to begin the week of September 20. They will likely roll out in the same order as initial doses, with health care workers, the elderly, and other vulnerable populations first in line. But when will Johnson & Johnson vaccine boosters be approved and recommended, if at all, for the 14 million Americans who received that single jab?

According to Timothy Brewer, MD, professor of medicine and epidemiology at UCLA, the short answer is that we don't yet know but should expect more information in the coming weeks. "The issue with the Johnson & Johnson booster is they just don't have data yet [on the J&J vaccine's long-term effectiveness]," he says. "But I suspect that booster recommendations will apply to Johnson & Johnson recipients as well once that data arrives."

We don't yet have this data because J&J vaccine administration didn't commence until two months after mRNA vaccine distribution began. It was also briefly paused due to side effect concerns. "The J&J vaccine was not administered in the U.S. until March of 2021, and we expect more data on J&J in the coming weeks," surgeon general Vivek Murthy, MD, said in a White House briefing on Wednesday. "With those data in hand, we will keep the public informed with a timely plan for J&J booster shots."

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In the meantime, if you're a J&J vaccine recipient who's worried, Dr. Brewer offers some clarity and comfort as you await a booster. He notes that even though data is limited (only 10 percent of the population has received the J&J vaccine), trials and population-based studies have shown that while J&J was slightly less protective against infection than the other two U.S. jabs, it was equally as effective in preventing severe illness, hospitalization, and death.

Additionally, Johnson & Johnson issued a news release that says it gave study participants a second vaccine dosage after six months and found that their antibody load was nine times higher than it was 28 days after the first dose. Even so, these are preliminary findings (other researchers haven't vetted them), and Johnson & Johnson must still submit these findings to the Food and Drug Administration (FDA).

Still, you might be wondering if it's advisable to get a different booster—e.g., Pfizer or Moderna—given that they'll likely be made available slightly earlier, and that they're slightly more protective. Dr. Brewer notes that data show those who mixed an adenovirus-based vaccine like J&J (but in this case, the AstraZeneca vaccine was studied, not J&J) with an mRNA vaccine did tend to have higher immune responses, but they also experienced more side effects. His recommendation as an epidemiologist: Wait until more data is available before deciding to mix dose types.

And Dr. Brewer wants to reiterate that J&J vaccine recipients are well-protected, even after one dose, so if that's the only vaccine available to you and you haven't yet been vaccinated at all, you should absolutely take it. "Johnson & Johnson remains an excellent choice for people who are thinking about being vaccinated and might find it hard to take a two-dose vaccine," he says. 

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