Covid-19 vaccine developers are making ever bolder assertions that the world will need yearly booster shots, or new vaccines to tackle concerning coronavirus variants, but some scientists question when, or whether, such shots will be needed.

In interviews with Reuters, more than a dozen influential infectious disease and vaccine development experts said there is growing evidence that a first round of global vaccinations may offer enduring protection against the coronavirus and its most worrisome variants discovered to date.

Some of these scientists expressed concern that public expectations around Covid-19 boosters are being set by pharmaceutical executives rather than health specialists, although many agreed that preparing for such a need as a precaution was prudent.

They fear a push by wealthy nations for repeat vaccination as early as this year will deepen the divide with...