New York: Early data from Moderna Inc’s COVID-19 vaccine, the first to be tested in the United States, showed that it produced protective antibodies in a small group of healthy volunteers, the company said on Monday.

The data comes from eight people who took part in a 45-subject safety trial that kicked off in March. The Moderna vaccine is one of more than 100 under development intended to protect against the novel coronavirus that has infected more than 4.7 million people globally and killed over 315,000.

Overall, the study showed the vaccine was safe and all study participants produced antibodies against the virus.

An analysis of the response in the eight individuals showed that those who received a 100 microgram dose and a 25 microgram dose had levels of protective antibodies to fend off the virus that exceeded those found in the blood of people who recovered from COVID-19, the illness caused by the coronavirus.

The news, issued in a release by the US biotechnology company, lifted shares of Moderna more than 22% and helped drive the broader stock market higher.

“These are significant findings but it is a Phase 1 clinical trial that only included eight people. It was designed for safety. Not for efficacy,” said Dr Amesh Adalja, an infectious disease expert at the Johns Hopkins Centre for health security who was not involved in the study.

The very early data offers a glimmer of hope for a vaccine among the most advanced in development.

Adalja said many glitches can occur between now and the time this vaccine is tested for efficacy in thousands of people. “What we do see is encouraging,” he said.

Scientists are trying to understand what level of antibodies will ultimately prove protective against the novel coronavirus, and how long that protection will last.

Moderna said the vaccine appeared to show a dose response, meaning that people who took the 100 mcg dose produced more antibodies than people who got the lower dose.

The vaccine has gotten the green light to start the second stage of human testing. Last week, US regulators gave the vaccine “fast-track” status to speed up the regulatory review.

In the Phase II, or midstage, trial designed to further test effectiveness and find the optimal dose, Moderna said it will drop plans to test a 250 mcg dose and test a 50 mcg dose instead.