Moderna Inc.’s vaccine candidate against COVID-19 protected against the virus in a trial that inoculated 16 monkeys, an encouraging step on the path to a defence for humans against the pandemic.

Two injections of the vaccine protected against heavy exposure to the virus at two different levels of dosage, Moderna said in findings published Tuesday in the New England Journal of Medicine. The primates didn’t show any sign of creating enhanced disease, a problem that has occasionally been associated with vaccines.

While the data is encouraging, a far bigger test is under way for Moderna, involving 30,000 humans. The phase 3 trial to determine the safety and efficacy of the vaccine will begin producing data in November or December. The vaccine uses messenger RNA, a synthetic form of genetic material from the virus designed to nudge the body’s immune system into attack mode. The U.S. government is providing US$955 million to help fund the vaccine’s development.

Moderna shares rose 1.7 per cent to US$81.24 at 3:50 p.m. in New York.