A fishing vessel that left Seattle in May returned with an unexpected catch: the first direct evidence in humans that antibodies to the coronavirus can thwart infection.
More than a hundred crew members aboard the American Dynasty were stricken by the infection over 18 days at sea. But three sailors who initially carried antibodies remained virus-free, according to a new report.
Although the study is small, it addresses one of the most important questions in the pandemic: whether the immune response to one bout with the virus protects against reinfection.
“Knowing the answer to this question is critical for vaccine design and epidemiology,” tweeted Jesse Bloom, an evolutionary biologist at the Fred Hutchinson Cancer Research Center in Seattle and one of the study’s authors.
The study was posted online last week and has not yet been published in a peer-reviewed journal. Still, the finding set off optimistic chatter among scientists, who have been relying on monkey studies for evidence of antibodies’ potency.
“I thought it was very exciting — good enough news that I was telling my family about it,” said Michal Tal, an immunologist at Stanford University who was not involved in the work.
Several research teams have reported that an encounter with the virus triggers a robust immune response in most people, including in those who may have been only mildly ill. And the vaccine candidates now in trials also seem to elicit strong neutralizing antibodies, the kind that can block the virus.
But the amount of those antibodies needed to prevent the virus from returning is unclear. Scientists measure neutralizing antibodies in titers, an indication of their concentration in the blood.
The three sailors who remained protected from the virus had widely varying titers; two had only moderate quantities, a finding the researchers said was reassuring.
“People have been so worried about the titers, and the titers going down,” Dr. Alexander Greninger, a virologist at the University of Washington in Seattle, said.
The results indicate even moderate titers prevented reinfection in a situation in which exposure to the virus was high, he said: “These are attainable titers, right? Hopefully, it’ll be helpful to see, and makes make me very optimistic about the vaccines.”
The American Dynasty carried 113 men and nine women. All crew members had been tested for both virus and antibodies as part of a routine screening before setting sail. (The researchers did not have access to the results from two members.)
The trawler returned to shore after 18 days at sea when a crew member became ill enough to need hospitalization. The sailors were tested for the presence of virus and antibodies again and for up to 50 days after their return.
The three sailors confirmed to have neutralizing antibodies did not test positive for the virus during the course of the study; 103 of the remaining 117 became infected.
These numbers may be small, but they’re highly significant, Dr. Greninger said.
“A lot of people, when they see this are like, ‘Oh come on, it could be due to random chance,’” he said. In fact, the likelihood that the results are just chance is extremely low, he added.
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Frequently Asked Questions
Updated August 17, 2020
Why does standing six feet away from others help?
- The coronavirus spreads primarily through droplets from your mouth and nose, especially when you cough or sneeze. The C.D.C., one of the organizations using that measure, bases its recommendation of six feet on the idea that most large droplets that people expel when they cough or sneeze will fall to the ground within six feet. But six feet has never been a magic number that guarantees complete protection. Sneezes, for instance, can launch droplets a lot farther than six feet, according to a recent study. It’s a rule of thumb: You should be safest standing six feet apart outside, especially when it’s windy. But keep a mask on at all times, even when you think you’re far enough apart.
I have antibodies. Am I now immune?
- As of right now, that seems likely, for at least several months. There have been frightening accounts of people suffering what seems to be a second bout of Covid-19. But experts say these patients may have a drawn-out course of infection, with the virus taking a slow toll weeks to months after initial exposure. People infected with the coronavirus typically produce immune molecules called antibodies, which are protective proteins made in response to an infection. These antibodies may last in the body only two to three months, which may seem worrisome, but that’s perfectly normal after an acute infection subsides, said Dr. Michael Mina, an immunologist at Harvard University. It may be possible to get the coronavirus again, but it’s highly unlikely that it would be possible in a short window of time from initial infection or make people sicker the second time.
I’m a small-business owner. Can I get relief?
- The stimulus bills enacted in March offer help for the millions of American small businesses. Those eligible for aid are businesses and nonprofit organizations with fewer than 500 workers, including sole proprietorships, independent contractors and freelancers. Some larger companies in some industries are also eligible. The help being offered, which is being managed by the Small Business Administration, includes the Paycheck Protection Program and the Economic Injury Disaster Loan program. But lots of folks have not yet seen payouts. Even those who have received help are confused: The rules are draconian, and some are stuck sitting on money they don’t know how to use. Many small-business owners are getting less than they expected or not hearing anything at all.
What are my rights if I am worried about going back to work?
What is school going to look like in September?
- It is unlikely that many schools will return to a normal schedule this fall, requiring the grind of online learning, makeshift child care and stunted workdays to continue. California’s two largest public school districts — Los Angeles and San Diego — said on July 13, that instruction will be remote-only in the fall, citing concerns that surging coronavirus infections in their areas pose too dire a risk for students and teachers. Together, the two districts enroll some 825,000 students. They are the largest in the country so far to abandon plans for even a partial physical return to classrooms when they reopen in August. For other districts, the solution won’t be an all-or-nothing approach. Many systems, including the nation’s largest, New York City, are devising hybrid plans that involve spending some days in classrooms and other days online. There’s no national policy on this yet, so check with your municipal school system regularly to see what is happening in your community.
Other experts agreed. “Just looking at the numbers, it becomes clear that it’s unlikely that all of these three people were protected by chance,” said Florian Krammer, an immunologist at the Icahn School of Medicine at Mount Sinai in New York.
Dr. Krammer and his colleagues are tracking antibody levels in people who have recovered from the coronavirus once to see at what point they might be vulnerable to reinfection. The team began with people in New York, but the virus is circulating at such low levels in the city now that Dr. Krammer and his colleagues have had to expand the study to other locations.
Data from vaccine trials also will identify the antibody titers required to disarm the virus. But in the meantime, “this is the first evidence in humans,” Dr. Krammer said. “It made my weekend.”
The study raised other questions. Based on the Abbott Architect assay, six of the 120 people tested before the boat’s departure had antibodies to the virus indicating prior exposure.
But when the researchers reanalyzed those samples using more sophisticated tests, only three of the six were confirmed to have antibodies, suggesting that three test results were false positives.
The Abbott test is advertised as returning fewer than one false positive for every 100 samples. “That’s a little concerning that the Abbott may be a little less specific than we thought,” Dr. Tal said.
The researchers also looked at antibodies in the blood, as most teams do. But those levels may not be the same as those in the nose or in saliva, the two major entry points for infection, Dr. Tal added.
“We’re looking in the wrong place,” she said. “If we want to look at protection from reinfection, we need to be looking in the nose.”