In the latest sign that the leading coronavirus vaccines may work well for older adults, researchers reported on Thursday that the vaccine being developed by AstraZeneca and the University of Oxford produced a similar immune response when tested in both older and younger adults.

The results, published in the journal The Lancet, come from 650 participants, 400 of them over the age of 56. The participants were enrolled in the Phase 2 component of an ongoing clinical trial in Britain. Results are expected soon from the study’s Phase 3 component, which will reveal how well the vaccine protected against Covid-19.

“We are getting very good immune responses — even in the over 70s, which look very similar to those in younger adults,” Andrew Pollard, the Oxford researcher leading the study, told reporters on Thursday. It is not yet known, however, whether vaccinated older adults will be able to sustain those immune responses over time.

Certain vaccines, including those that protect against some viruses that cause the seasonal flu, can be less effective for older adults. That has raised concerns that Covid-19 vaccines won’t work as well in that age group, which is especially vulnerable to the disease.

But results this week are boosting hopes that older adults will respond strongly to the leading vaccine candidates.

Moderna announced on Monday that a preliminary analysis found its vaccine to be 94.5 percent effective. The vaccine appeared equally safe and effective in all groups assessed.

And Pfizer, which on Wednesday announced the first complete results from a late-stage vaccine trial, said its vaccine was 94 percent effective in older adults, compared to 95 percent in the study overall.

— Rebecca Robbins The New York Times