J.&J. Vaccine May Be Less Effective Against Delta, Study Suggests

Many who received the shot may need to consider boosters, the authors said. But federal health officials do not recommend second doses.

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 on Tuesday. Although troubling, the findings result from experiments conducted with blood samples in a laboratory, and may not reflect the vaccine’s performance in the real world. But the conclusions 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. 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.