Coronavirus super-spreader event suggests individuals who’ve recovered are susceptible to reinfection unless they develop neutralizing antibodies.
A widespread coronavirus outbreak aboard Seattle-based fishing boat, FV American Dynasty, may offer the first set of direct evidence that antibodies can grant protective immunity from the coronavirus, according to a new report. Crewmembers were studied by researchers from the University of Washington and Fred Hutchinson Cancer Research Center before and after the boat’s eighteen-day voyage in May that caused more than 85 percent those on board to become infected. Blood samples were collected and showed that three of the 122 people had a positive antibody response, indicating they had been previously infected by COVID-19 and had recovered. “While 104 of the 120 crew members would test positive for the coronavirus – the three who had neutralizing antibodies beforehand didn’t become infected,” researchers discuss in the findings posted on MedRxiv.
“It’s a strong indication that the presence of neutralizing antibodies is associated with protection from the virus,” said co-author Dr. Alex Greninger. “It’s hopeful news.”
“The blood testing of nearly the entire crew and the stunning rate of infection in close quarters means it’s likely the three were exposed to the virus during the outbreak,” said Mark Slifka, an immunologist and vaccine developer at Oregon Health & Science University.
“While this is a small study, it offers a remarkable, real-life, human experiment,” Danny Altmann, professor of immunology at Imperial College London, wrote in a commentary on the report. “Who knew immunology research on fishing boats could be so informative?”
In another commentary, Jonathan Ball, a professor of molecular virology at University of Nottingham who was not involved in the research, said the glimpse into how to achieve immunity “suggests that individuals who have had a prior exposure to virus are susceptible to reinfection unless they have appreciable levels of neutralizing antibodies. This gives us an important insight into the type of immunity that might protect from future infection.”
Greninger added, “The fifteen other crew members who never became infected possibly had jobs on the boat that protected them from exposure.” He added that “three other crewmembers had antibodies that binded to the capsule of the novel coronavirus but failed to block infection.”
The Fred Hutchinson Cancer Research Center also recently reported the coronavirus is “most likely transferred through super-spreader events, and that 80% of those who test positive for the virus never infect anyone else,” according to Dr. Josh Schiffer, an infectious disease physician, who added, “The research is preliminary and subject to revision, but important enough to be presented to colleagues in the field for their consideration…What I mean by that is that there are a relatively small, but really important proportion of spreading events where one person infects 10 people, or sometimes 50 people, or sometimes 100 people. Yet 80% of people with this virus don’t infect anybody.”
Research also shows, if those “at their peak contagious point happens to be with a crowd of people, particularly indoors or around people not wearing masks, a ‘super-spreader event ‘can happen.” This was the case on the crowded fishing boat.
“The message that seems to be emerging is that it’s not actually that rare for somebody to have this potential,” explained Dr. Schiffer. “In fact, you know, and probably a quarter of people who are infected shed at a high enough level, where if they were to walk into the wrong place at the wrong time, they could be a super spreader, but it’s not very common. It really requires, you know…there’s so many examples now. They’re the fishing boats, the meatpacking plants, the prisons, the elder care facilities where this has happened.”
Dr. Schiffer said super-spreader events happen by chance, saying, “In my opinion, it’s bad timing.”