The first participants in a phase one trial of AstraZeneca’s potential COVID-19 drug have been dosed, according to the British drugmaker.

The trial will include up to 48 healthy participants in the United Kingdom aged 18 to 55 and focus on the safety and tolerability of the drug, which is called AZD7442. It is a combination of two monoclonal antibodies derived from patients who had recovered from the coronavirus. The company said the antibodies “should afford at least six months of protection from COVID-19.”

“This trial is an important milestone in the development of our monoclonal antibody combination to prevent or treat COVID-19,” Mene Pangalos, executive vice president of biopharmaceuticals research and development at AstraZeneca, said in a statement. “This combination of antibodies, coupled to our proprietary half-life extension technology, has the potential to improve both the effectiveness and durability of use in addition to reducing the likelihood of viral resistance.”

AstraZeneca is also working on a vaccine with the University of Oxford. It generated an immune response in healthy participants aged 18 to 55 during an early trial. Researchers said they found no safety concerns with the vaccine, which produced its strongest immune response after two doses were administered to patients.

The vaccine is in its final phase three trial. The Trump administration is considering fast-tracking approval of the vaccine ahead of the November election, according to The Financial Times.

However, leading infectious disease expert Anthony Fauci told Reuters this week that giving out a vaccine under emergency use guidelines before it has completed large clinical trials is a bad idea.

“One of the potential dangers if you prematurely let a vaccine out is that it would make it difficult, if not impossible, for the other vaccines to enroll people in their trial,” Fauci said.