NEW YORK (CBSNewYork) — The Delta variant of the COVID-19 virus continues to spread. It now constitutes 83% of the COVID cases in the U.S.

And now, as CBS2’s Dr. Max Gomez reported Wednesday, a preliminary study not yet peer reviewed suggests that the Johnson & Johnson vaccine may not be as effective against the Delta variant as the other two authorized vaccines.

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The J&J vaccine has been given to more than 13 million people, many of whom have always been somewhat anxious about whether they are as protected against the Delta or Lambda variants as the people who received the Pfizer or Moderna vaccines. That anxiety has been made worse by the latest NYU study that has just been posted to what’s known as a “pre-print” site, meaning it has not been peer reviewed for publication in a scientific journal.

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Those conclusions differ from smaller clinical results released by J&J earlier this month that said a single dose of their vaccine did protect against Delta, even eight months after inoculation.

Those differences could be because the new study looked at antibodies in the lab compared to real world immunity in people, which would include T-cell immunity. Peer review would help determine that contribution to protection.

Gomez spoke exclusively with the senior author of the NYU study, who said there have not been significant breakthrough infections in those vaccinated with J&J.

“I think people that have gotten the J&J vaccine, I think they can feel fine. They’ve gotten a highly effective vaccine. It’s safe. It’s tolerable. It’s an important part of our armamentarium,” Dr. Mark Mulligan said.

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Experts also made it clear that the J&J vaccine still provides protection against all variants of the coronavirus, just not as much, perhaps, as Pfizer and Moderna. What’s not yet known is whether mixing and matching different brands is safe as boosters.

There is, however, some not-yet-published, not-yet-peer-reviewed data from the United Kingdom that suggests that mixing and matching brands — getting a Moderna or Pfizer shot after a virus shot such as J&J — is not only safe, but also produces a much stronger immune response and so may even be advisable. But we won’t know that for sure until data is submitted and peer-reviewed, which will hopefully happen soon.

Dr. Max Gomez