NEW YORK (CBSNewYork) — A second dose of Johnson & Johnson‘s vaccine appears to significantly raise its protection against COVID-19.

J&J has already submitted its clinical trial data to the Food and Drug Administration, asking for authorization to give a second booster shot to the nearly 15 million Americans who’ve already received its one-shot vaccine, CBS2’s Dr. Max Gomez reported Tuesday.

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J&J had long believed that a second shot of its engineered, virus-based vaccine would boost immunity to COVID-19. That’s why, even after it had received emergency use authorization for it’s one-shot vaccine, it was already running a very large, Phase 3 clinical trial using a second booster dose.

And now that the data is in, the results are extremely positive.

COVID VACCINE

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A booster shot at two months of the J&J vaccine produced 94% protection against moderate to severe COVID-19, up from 74% after a single shot. And that second shot showed 100% efficacy against severe-critical COVID-19, although that number had a wide range of variability.

Perhaps more encouraging news comes from the longevity of the protection. While the mRNA vaccines from Pfizer and Moderna have shown waning protection with time, the J&J vaccines have shown little sign of weakening.

A second trial comparing nearly 400,000 vaccinated people to 1.5 million unvaccinated ones showed that after five months the J&J vaccine protection against hospitalization remained steady at around 81%.

And in still another study, researchers reported that antibodies rose nine times higher one week after the booster dose and continued to climb to 12 times higher, four weeks after the booster.

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These increased levels of protection included when the Delta variant became dominant in the U.S. J&J said that the new data suggests that a booster shot at six months or even later will significantly increase the protection against COVID-19 people got after the first shot of its vaccine.

Dr. Max Gomez