There’s more good news in the worldwide race for a COVID-19 vaccine. The vaccine developed by scientists from Oxford University, in partnership with AstraZeneca, has proven to be safe and produce a strong immune response in early tests. The trial involved 1,077 people, and found that the vaccine produced antibodies and white blood cells that fight the virus, and only caused mild side effects.

In addition to producing neutralizing antibodies, which block infection, the vaccine also boosted T-cells, which help destroy cells that have been overtaken by the virus. According to Dr. Adrian Hill, director of Oxford’s Jenner Institute, the vaccine appeared to produce a similar level of antibodies to those produced in people who have naturally recovered from the virus.

“We are seeing good immune response in almost everybody,” said Hill. “What this vaccine does particularly well is trigger both arms of the immune system.There’s increasing evidence that having a T-cell response as well as antibodies could be very important in controlling COVID-19.”

These early trials are designed to test the vaccine’s safety and whether it produces an immune response. They do not, however, definitively prove that the vaccine will protect against infection. That task falls to the current trial, which involves thousands of participants in the UK, South Africa, and Brazil.

Although there are several vaccines in various stages of development around the world — including in the US where the first COVID-19 vaccine tested on humans showed promising results last week — the Oxford vaccine remains one of the frontrunners, with a target delivery date of winter 2020.