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Nearly 90,000 people in Massachusetts have tested positive for the virus that causes COVID-19. But it's still unclear if having had the virus makes a person immune to further infection, and if so, for how long. As the state expands its re-opening and looks toward the possibility of schools opening in the fall, these questions become more pressing.
Two studies on monkeys published Wednesday in the journal Science suggest that having antibodies to the novel coronavirus — either from previous infection or from certain prototype vaccines — offer protection from getting re-infected. The work was led by researchers at Beth Israel Deaconess Medical Center (BIDMC).
“Overall, this is very good news," said senior author Dan Barouch, director of the Center for Virology and Vaccine Research at BIDMC. "This shows, at least in a proof-of-concept setting, that natural immunity as well as vaccine-induced immunity can exist."
In one study, researchers showed that all nine rhesus macaques exposed to the SARS-CoV-2 virus developed antibodies against it. The researchers re-exposed the monkeys to the virus more than a month later, and while some virus did show up in the animals' noses and lungs, each had a strong immune response and few symptoms.
"If these animal data are indeed translatable to humans, then we would also predict that humans — or at least a large fraction of humans — who are infected and then recover likely will resist a challenge," said Barouch.
In the second study, the researchers tested six prototype vaccines in 25 adult rhesus macaques, while 10 monkeys received a placebo. (The vaccines they used are prototypes for research purposes only, and not being developed into human vaccines. Barouch said that other vaccines under development will likely perform better.) The vaccinated monkeys developed "neutralizing" antibodies in their bloodstream. Researchers then exposed all 35 animals to the virus and measured their response. Eight of the 25 vaccinated monkeys had no detectable virus at any point following exposure, while the other monkeys showed levels of virus lower than the control group.
In addition, monkeys with higher levels of antibodies in their blood had lower levels of the virus in their bodies, which suggests that antibody levels may be a useful marker of protection against the novel coronavirus.
Barouch emphasized that animal studies do not always apply to humans, and said that because the studies were relatively short, researchers couldn't determine whether any antibody protection was short- or long-lived.
"These studies are a first step," he said, "but not the last step."
This article was originally published on May 20, 2020.
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