Sure enough, other data supports the notion that vaccine immunity is not waning much.

The ratio of positive Covid tests among older adults and children, for example, does not seem to be changing, Dowdy notes. If waning immunity were a major problem, we should expect to see a faster rise in Covid cases among older people (who were among the first to receive shots). And even the Israeli analysis showed that the vaccines continued to prevent serious Covid illness at essentially the same rate as before.

“If there’s data proving the need for boosters, where is it?” Zeynep Tufekci, the sociologist and Times columnist, has written.

Part of the problem is that the waning-immunity story line is irresistible to many people. The vaccine makers — Pfizer, Moderna and others — have an incentive to promote it, because booster shots will bring them big profits. The C.D.C. and F.D.A., for their part, have a history of extreme caution, even when it harms public health. We in the media tend to suffer from bad-news bias. And many Americans are so understandably frightened by Covid that they pay more attention to alarming signs than reassuring ones.