A COVID vaccine candidate developed by the University of Oxford with AstraZeneca has produced a robust immune response in older adults and the elderly, those at highest risk of severe illness.

Findings on blood tests carried out on a subset of older participants echo data released in July that showed the vaccine generated robust immune responses in healthy adults ages 18 to 55, Astra said Monday. Older patients have been hardest hit by the pandemic, with the vast majority of deaths occurring in those over 60.

The Astra-Oxford vaccine candidate is one of several front-runners in the race for protection against the virus. A late-stage trial of the shot was restarted last week in the U.S. after a temporary halt that followed a participant’s illness in a separate U.K. study. The trial in Britain and others around the world had already resumed.

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The July results, from an earlier trial phase, showed that the vaccine increased levels of both protective neutralizing antibodies and immune T-cells that target the virus.

Trial participants ages 56 and over also showed low levels of adverse reactions, Astra said. The roughly 7-week U.S. trial halt had raised questions about safety.

“It is encouraging to see immunogenicity responses were similar between older and younger adults and that reactogenicity was lower in older adults, where the COVID-19 disease severity is higher,” Astra said in an emailed statement. “The results further build the body of evidence for the safety and immunogenicity” of the vaccine candidate.