This Vaccine Protects You the Least From the Delta Variant, New Study Says

The results find that a booster might be necessary to stop the latest variant.

After months of progress, the arrival and spread of the Delta variant is creating a serious obstacle to finally ending the COVID-19 pandemic. According to the U.S. Centers for Disease Control and Prevention (CDC), the "hypertransmissible" strain is responsible for 83.2 percent of new cases that had been genetically sequenced as of July 17. As a result, health experts are now urging those who remain unvaccinated to get their shots to stop the current outbreaks that are largely affecting areas with low vaccination rates. But while mounting research has found some shots are effective at stopping the Delta variant, a new study has found that the Johnson & Johnson vaccine protects you the least from the highly contagious strain.

RELATED: This Is How Much the Moderna Vaccine Really Protects You, New Study Says.

According to the results, which were published online by bioRxiv but have not yet been peer-reviewed nor published in a journal, the single-shot dose may be less effective against both the surging Delta variant and the emerging Lambda variant than two-dose mRNA-style vaccines Pfizer and Moderna. The study authors conclude that data suggests those who received the Johnson & Johnson (J&J) vaccine may need a follow-up shot to protect themselves.

"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, PhD, the study's lead researcher and a virologist at N.Y.U.'s Grossman School of Medicine, told The New York Times.

The results did not surprise some other experts, who cite the high efficacy rates of double-shot vaccines. "I have always thought, and often said, that the J&J vaccine is a two-dose vaccine," John Moore, a virologist at Weill Cornell Medicine in New York, told The Times.

RELATED: Pfizer Says Its Vaccine Starts Losing Efficacy After This Long.

But some point out that the results, which were found using blood samples in a laboratory, don't accurately reflect conditions in the real world. Seema Kumar, a spokeswoman for J&J Studies sponsored by the company, told The Times that the study's findings "do not speak to the full nature of immune protection" and that other small studies commissioned by Johnson & Johnson have found that the vaccine "generated strong, persistent activity against the rapidly spreading Delta variant."

The CDC responded to the study by reiterating its previously issued statement that "Americans who have been fully vaccinated do not need a booster at this time." But other experts are urging those who got the single-dose vaccine to get another shot.

"AstraZeneca, when combined with a Pfizer or Moderna booster, is showing tremendous levels of protection against Delta, in terms of the antibody levels that are generated in patients," Vin Gupta, MD, a professor at the University of Washington's Institute for Health Metrics and Evaluation, said during a July 20 appearance on CNBC. "I do think that those one-shot J&Jer's should be given the opportunity, while we complete our clinical trial … I'm already telling my patients to do it, if they can get access to it."

When asked to clarify how at-risk those who had only received a single Johnson & Johnson shot were, Gupta said: "I think you're protected, likely from the hospital and severe outcomes from say, the Delta variant, based on what data we do have. [But] I do not think you have the same level of protection to transmit the virus than somebody who received two doses of the vaccine like Pfizer or Moderna. I think that is pretty clear at this point."

RELATED: If You Have This, Your Pfizer or Moderna Vaccine Is Less Effective, Study Finds.

Zachary Mack
Zach is a freelance writer specializing in beer, wine, food, spirits, and travel. He is based in Manhattan. Read more
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