An experimental coronavirus vaccine made by biotech company Moderna is producing promising immune responses and appears safe in the first 45 people who received it, researchers have reported in The New England Journal of Medicine.

Dr Anthony Fauci, the US government’s top infectious disease expert, called the results “good news”, noting that the study found no serious adverse events and the vaccine produced “reasonably high” levels of virus-killing or neutralising antibodies.

“If your vaccine can induce a response comparable with natural infection, that’s a winner,” Dr Fauci said in a telephone interview. “That’s why we’re very pleased by the results.”

Moderna’s vaccine candidate was developed by researchers at the the National Institute of Allergy and Infectious Diseases, where Dr Fauci is the director.

Volunteers who got two doses of the vaccine in March had high levels of virus-killing antibodies comparable to people who had recovered from COVID-19, the research team reported.

“This is an essential building block that is needed to move forward with the trials that could actually determine whether the vaccine does protect against infection,” said Dr. Lisa Jackson of the Kaiser Permanente Washington Research Institute in Seattle, who led the study.

These early results, published in the New England Journal of Medicine on Tuesday (local time), showed that the vaccine worked to trigger an immune response with mild side effects – fatigue, chills, headache, muscle pain, pain at the injection site.

Some of those reactions are similar to coronavirus symptoms but they are temporary, lasting about a day and occur right after vaccination, researchers noted.

“Small price to pay for protection against COVID,” said Dr. William Schaffner of Vanderbilt University Medical Center, a vaccine expert who wasn’t involved with the study.

He called the early results “a good first step,” and is optimistic that final testing could deliver answers about whether it’s really safe and effective by the beginning of next year.

The vaccine requires two doses, a month apart.

It is the first US vaccine candidate to publish results in a peer-reviewed medical journal.

The US government is aiming to have results around the end of the year.

This would be record-setting speed for developing a vaccine.

-with agencies