Could a discovery aboard an American Seafoods factory trawler whose crew tested positive for the coronavirus be the first direct evidence that antibodies can protect people from COVID-19 reinfection?

In May, American Seafoods reported that 85 crew members aboard its American Dynasty pollock vessel tested positive for COVID-19.

Blood samples collected before the vessel sailed showed that three of the people aboard had robust levels of neutralizing antibodies — the type that block the virus from entering human cells — indicating they had been previously infected and recovered, reports the Seattle Times. All three were spared during the shipboard outbreak, which quickly spread to more than 85 percent of the crew.

“It’s a strong indication that the presence of neutralizing antibodies is associated with protection from the virus,” said Dr. Alex Greninger, of the UW Medicine Clinical Virology Laboratory and co-author of a report posted on the preprint server MedRxiv that has not yet been peer-reviewed.

“It’s hopeful news," she told the newspaper.

Researchers are generally confident that prior infection will provide some level of immunity. But what constitutes a protective immune response and how long immunity lasts is still unknown, officials say.