The FDA issued another warning about the J&J vaccine. How much will this increase doubt among the unvaccinated?

The U.S. Food and Drug Administration is planning to warn that Johnson & Johnson’s one-dose COVID-19 vaccine can lead to an increased risk of a rare neurological condition known as Guillain-Barré syndrome. The warning does not involve the Moderna or Pfizer vaccines, which are much more widely used in the United States.

This will not help calm nerves or quiet vaccine doubters, though it could send a signal that the FDA is serious about ensuring the public knows about even small risks.

People familiar with the FDA’s plans tell The New York...