The results, published Thursday in The Lancet medical journal, shed more light on preliminary data released in recent months showing the experimental shot generated an immune response in older people, who are at highest risk of severe illness. Researchers are still eagerly awaiting late-stage trial results that will show whether the Astra-Oxford vaccine can meet the high bar set by front-runners Pfizer Inc. and Moderna Inc.

Those findings will follow a flurry of positive news on the vaccine front. Pfizer, working with Germany’s BioNTech SE, said Wednesday that a final analysis of trial data showed its Covid19 vaccine was 95% effective, paving the way for the company to apply for the first U.S. regulatory authorization for a coronavirus shot within days. Moderna’s appears equally effective.

The results of Oxford’s phase 2 study show that the vaccine is better tolerated in older people and produces a similar immune response in old and young adults. The study involved 560 adults, including 240 over the age of 70. That follows findings in older participants unveiled last month and data in July that showed the vaccine generated robust immune responses in adults ages 18 to 55. Older patients have been hardest hit by the pandemic, with the vast majority of deaths occurring in those over 60.

“Inducing robust immune responses in older adults has been a long-standing challenge,” Angela Minassian, an investigator at Oxford, wrote in a statement. “To show this vaccine technology is able to induce these responses — in the age group most at risk from severe Covid-19 disease — offers hope that vaccine efficacy will be similar in younger and older adults.”

Oxford expects final-stage efficacy results in the coming weeks, according to its statement.

The study shows the vaccine causes few side effects and provokes a response in T-cells that target the virus within 14 days of the first dose and a protective antibody response within 28 days of the booster dose, according to the report. Neutralizing levels were achieved by 14 days after a boost vaccination in 208 of 209 recipients.