Company honchos pointed to a new study which found that five out of six primates who got the single-dose shot were protected from infection when exposed to the coronavirus, as measured by its presence in nasal swabs.

“This gives us confidence that we can test a single-shot vaccine in this epidemic and learn whether it has a protective effect in humans,” Dr. Paul Stoffels, J&J’s chief scientific officer told Reuters.

The study, published Thursday in the journal Nature, also found that six out of six of the monkeys were protected from lung disease related to COVID-19.

J&J said it will now test its vaccine candidate on more than 1,000 healthy adults aged 18 to 55, along with people over the age of 65 in early-stage human trials in the United States and Belgium.

In other cases, researchers found a second shot significantly increases protection from disease — but a single-shot vaccine is crucial during a pandemic because it reduces issues such as getting people to come back for a second dose, Stoffels said.

The company plans to tackle the question of whether the vaccine should be a one- or two-dose shot during phase one of the human trial, he said.

The clinical trial is one of more than 30 human trials for coronavirus vaccines that are underway worldwide, according to the New York Times, which noted some experts were optimistic about the results of the new study.

“This week has been good — now we have two vaccines that work in monkeys,” said Angela Rasmussen, a virologist at Columbia University who was not involved in the research. “It’s nice to be upbeat for a change.”

The US government is pouring $456 million into J&J’s vaccine development as part of an effort to speed along production of a vaccine for COVID-19, which has killed more than 667,000 people worldwide, including more than 150,000 Americans, according to Johns Hopkins University data.