The coronavirus vaccine made by Johnson & Johnson is much less effective against the delta and lambda variants than against the original virus, according to a new study posted online Tuesday.
The findings add to evidence that the 13 million people inoculated with the J&J vaccine may need to receive a second dose — ideally of one of the mRNA vaccines made by Pfizer-BioNTech or Moderna, the authors said.
But the conclusions are at odds with those from smaller studies published by Johnson & Johnson earlier this month suggesting that a single dose of the vaccine is effective against the variant even eight months after inoculation.
The new study has not yet been peer reviewed nor published in a scientific journal, and relied on laboratory experiments. But it is consistent with observations that a single dose of the AstraZeneca vaccine — which has a similar architecture to the J&J vaccine — shows only about 33% efficacy against symptomatic disease caused by the delta variant.
Other experts said the results are what they would have expected, because all of the vaccines seem to work better when given in two doses. “I have always thought, and often said, that the J&J vaccine is a two-dose vaccine,” said John Moore, a virus expert at Weill Cornell Medicine in New York.
Moore pointed to several studies in monkeys and people that have shown greater efficacy with two doses of the J&J vaccine, compared with one dose. He said the new study was particularly credible because it was published by a team with no ties to any of the vaccine manufacturers.
But the data from the new study “do not speak to the full nature of immune protection,” said Seema Kumar, a spokesperson for J&J. Studies sponsored by the company indicate that the vaccine “generated strong, persistent activity against the rapidly spreading delta variant,” she said.