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A small lab study suggests that Johnson & Johnson’s COVID-19 vaccine may be less effective against the Delta variant. Experts are split on what it means

A health care worker carried a tray with doses of the Johnson & Johnson COVID-19 vaccine.Eva Marie Uzcategui/Bloomberg

A new study that found the Johnson & Johnson COVID-19 vaccine produced a weaker antibody response against the Delta variant compared to two-dose, mRNA regimens is eliciting varied reactions from experts, with some saying it signals a possible need for a booster shot and others saying the lab experiment’s findings may not apply to real life.

The study, conducted by researchers from New York University, compared antibody responses to the Delta variant and the original strain of the virus in people who received vaccines from Pfizer, Moderna, and Johnson & Johnson. It was a small experiment that analyzed antibody responses in 10 recipients of Johnson & Johnson’s vaccine, eight recipients of Moderna’s vaccine, and nine recipients of Pfizer’s vaccine. The study was not peer reviewed or published in a journal; a preprint version was posted on Tuesday.


The study concluded that the antibody response against Delta in those who received the Johnson & Johnson vaccine was lower than those who received either Pfizer’s or Moderna’s. The study’s authors said the lower antibody response in the Johnson & Johnson vaccine “could result in decreased protection against infection.”

About 284,000 people in Massachusetts have received the J&J vaccine, according to data from the state Department of Public Health.

Some experts said the findings reinforced the need for recipients of the Johnson & Johnson shot to receive a second dose, either of the J&J shot or one of the vaccines that use mRNA technology, like the Pfizer or Moderna vaccines.

“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,” Nathaniel Landau, a virologist at NYU’s Grossman School of Medicine who led the study, told The New York Times.


Dr. Vin Gupta, an assistant professor of health metrics sciences at the University of Washington, told CNBC that the study shows that “it’s hard to believe that one dose of J&J is equivalent to two doses of Pfizer or two doses of Moderna.”

Gupta said the AztraZeneca vaccine, which has a similar make up to Johnson & Johnson’s vaccine but has not been approved for emergency use by Unites States health officials, has been shown to “heighten protection” when combined with Pfizer or Moderna. Gupta said he thinks it’s time for public health agencies to issue guidance allowing those who have received the J&J vaccine to get a second dose of Pfizer or Moderna vaccines if they choose to.

The Centers for Disease Control and Prevention and Food and Drug Administration said in a joint statement issued earlier this month that the agencies are currently not recommending booster shots for fully vaccinated people.

“Americans who have been fully vaccinated do not need a booster shot at this time,” the statement said. “FDA, CDC, and NIH are engaged in a science-based, rigorous process to consider whether or when a booster might be necessary.”

Gupta added that he is already urging his patients who were vaccinated with Johnson & Johnson’s vaccine to get a second shot, of either the Pfizer or Moderna vaccines, if they can access it.

Dr. Jonathan Reiner, a cardiologist and professor at the George Washington School of Medicine & Health Sciences, said on Twitter that it is time for the CDC to “prioritize answering the question of whether the 13 million people vaccinated with J&J need a booster.”


Dr. Michael Lin, a professor of neurobiology and bioengineering at Stanford University, said on Twitter that the study reinforces his previous opinion that boosters “should be considered” for those who received the Johnson & Johnson vaccine because of the Delta variant.

Other experts said the way people who are vaccinated with the Johnson & Johnson vaccine respond to the virus in the real world, not just in laboratory tests, is an important consideration.

Dr. Shira Doron, an infectious disease physician and epidemiologist at Tufts Medical Center, told WCVB on Tuesday that she does not “put a lot of stock” into studies that are solely based on laboratory data.

“We are looking for clinical data,” Doron said, “and we do not have clinical data that suggest that people who receive J&J are at a greater risk than people who have received mRNA vaccines, especially when it comes to what counts, which is severe disease, hospitalization, and death.”

She added that antibody levels “do not tell the whole story when it comes to being effective against infection.”

Dr. Philip Grant, an infectious disease doctor and assistant professor of medicine at Stanford University, echoed Doron’s comments, saying “this type of lab study isn’t really what we’re looking for. We’re looking for more and more real world data of vaccines over time.”


Grant, who is also a principal investigator for ongoing Johnson & Johnson vaccine trials, told ABC7, a Chicago-based station, said that a larger concern is who is getting sick with the virus in the real world, which data show are people who are unvaccinated.

Dr. David Agus, a professor of medicine and engineering at the University of Southern California, called the study “meaningless” and said those who received the Johnson & Johnson vaccine shouldn’t be worried during an appearance on “CBS This Morning.”

The study, Agus noted, only looked at antibody levels, not T cells, “which are the dominant way you respond to vaccines.”

Dr. Peter Chin-Hong, an infectious disease physician and professor at the University of California, San Francisco, said lab studies do not necessarily translate to real life applications.

“We’ve seen in previous studies that lower levels of antibodies do not correlate with how people deal with disease as humans, so you can’t extrapolate, necessarily, laboratory-based studies to what happens in real life,” Chin-Hong told ABC10 news, a San Diego-based station.

Andrew Pekosz, a virologist and professor at the Johns Hopkins Bloomberg School of Public Health, said it’s important to “look in the real world” and see what the disease rate is in people who are inoculated with Johnson & Johnson’s vaccine.

“So far the signatures in the real world are that the J&J vaccine is protecting against severe disease mediated by COVID-19,” Pekosz told Bloomberg News. “I think the signs are good that the vaccine is going to protect against those very severe cases, but it’s something to keep in mind as we go forward and the discussion about boosters come together.”


Pekosz said that whether the J&J vaccine is a candidate for boosters “could be a discussion point for the fall.”

The lab study’s findings counter a small study conducted late last year that found that Johnson & Johnson’s vaccine provides protection against eight variants, including Delta.

In a statement to The New York Times, a Johnson & Johnson spokeswoman said that the data from the NYU study “do not speak to the full nature of immune protection,” and studies sponsored by the company indicate that the vaccine “generated strong, persistent activity against the rapidly spreading Delta variant.”

The Delta variant now accounts for about 83 percent of COVID-19 cases in the United States, CDC director Rochelle Walensky said on Tuesday. Experts have said the highly transmissible variant could be behind the recent rise of COVID-19 cases across the country.

Amanda Kaufman can be reached at amanda.kaufman@globe.com. Follow her @amandakauf1.