Lack of full approval also helps feed a misunderstanding. Adverse reactions to some drugs can indeed occur long after we start taking them, especially after long-term use. However, vaccination is a one-time event (or two, if you count the booster). Immediate side effects, like allergic reactions, would occur fairly soon after inoculation. That’s why people are asked to spend 15 minutes in a waiting room postvaccination or 30 minutes if they’ve had a history of allergic reactions. There are also questions about immune system reactions that can take longer to appear. However, as the immunologist Andrew Croxford explained, medical experts have learned to expect such problems within the first few weeks and months after vaccination. Regulators require six months of safety data, not more. They have that now.

The F.D.A. said it needs to complete “a high-quality review and evaluation,” and it does. But it has the data to do that quickly. The safety data on these vaccines is comparable to that of many fully approved vaccines. This is not to mention the evidence from hundreds of million doses administered in the United States alone.

Given the severe threat the Delta variant poses to the unvaccinated, the risk-benefit calculation is especially stark, and the need for full approval is even more urgent.