Both studies, which appear to be among the first peer-reviewed papers studying immunity to COVID-19 in primates, were published Wednesday in the journal Science.
Dr. Dan Barouch, head of Beth Israel’s Center for Virology and Vaccine Research and lead author of the studies, said more research must be done to determine whether the findings apply to humans. But he’s hopeful, given that humans and rhesus macaque monkeys share 93 percent of the same genetic makeup.
“We have to be careful about making predictions for humans,” said Barouch, who is also affiliated with the Ragon Institute of Massachusetts General Hospital, MIT and Harvard University. “But I can say these data increase our optimism that natural immunity and vaccine-induced immunity can be achieved in humans.”
Neither study determined whether the immunity response is permanent or how long it may last. Still, other vaccine experts were buoyed by the findings.
Dr. Louis Picker, associate director of the Vaccine and Gene Therapy Institute at Oregon Health & Science University, said the studies “convinced me that this is an infection that will be controllable with vaccination.”
Barouch’s laboratory is working on an experimental coronavirus vaccine with Johnson & Johnson that has received a pledge of more than $1 billion in funding from that company and the Biomedical Advanced Research and Development Authority, a federal agency.
That vaccine uses a common cold virus to deliver a coronavirus antigen into cells to stimulate the immune system. It’s expected to enter clinical trials by September and was not the subject of either paper.
One of the studies involved nine adult monkeys. Researchers infected their noses and lungs with SARS CoV-2, the virus that causes COVID-19.
The virus quickly spread into their upper and lower respiratory tracts. The nine monkeys developed viral pneumonia, but all recovered within 28 days.
A week later, researchers exposed the monkeys to the virus a second time. Although the scientists were able to detect tiny amounts of the virus in the lungs of some of the monkeys, none of the animals got sick. Their immune systems protected them.
“It has long been suspected that there would be natural protective immunity [after recovery from COVID-19] because most viruses do that, but that’s not always the case,” said Barouch, who cited HIV as a notable exception. “Our team found this data very compelling.”
If the finding was confirmed in humans, it might fuel calls for “immunity passports” for people who recover from COVID-19 and test positive for the antibodies. That idea that has been floated by some scientists and governments as a way to enable people who fight off the disease to return to work.
On April 24, the World Health Organization discouraged that, saying, “There is currently no evidence that people who have recovered from COVID-19 and have antibodies are protected from a second infection.”
The other study by Barouch’s researchers involved 35 monkeys ― 25 vaccinated against the virus and 10 that weren’t.
The vaccinated monkeys received one of six prototypes of DNA vaccines developed by his lab for the experiment. Each monkey got two doses.
To provoke an immune response, each prototype used the genetic code for portions of the protein that scientists believe the coronavirus uses to invade cells.
None of the prototypes are among dozens of experimental vaccines that have been developed by drug companies for testing in humans. Indeed, many scientists are skeptical of the clinical potential of DNA vaccines, and none has ever been licensed.
Nonetheless, all of the vaccinated monkeys developed antibodies, some at levels comparable to those made by the monkeys that recovered from COVID-19 in the other study.
Researchers then infected the 25 vaccinated monkeys, as well as the 10 that hadn’t been vaccinated. None of the vaccinated monkeys developed high levels of the virus in their lungs. All 10 of the unvaccinated monkeys did.
Dr. Nelson Michael, director of the Center for Infectious Diseases Research at the Walter Reed Army Institute of Research and a member of the White House Coronavirus Task Force, said he was impressed that the DNA vaccines protected all the monkeys because such vaccines generally aren’t very effective.
“If a DNA vaccine can work, then that really tells you this is probably doable,” said Michael, whose institute is testing another type of vaccine on mice.
Barouch’s researchers also found a direct link between the level of antibodies in the vaccinated monkeys and the level of protection from infection, Michael said.
“That’s the holy grail of vaccine development,” Michael said. “If you can figure out a lab test that would accurately predict who’s likely to be protected and who’s not likely to be protected, that’s huge.”
Picker, the vaccine expert at Oregon Health & Science University, said no vaccine is 100 percent effective. Even the vaccine for measles is considered about 97 percent effective after two doses, according to the Centers for Disease Control and Prevention.
More than 100 experimental vaccines are in the works as drug firms, academic laboratories, and governments around the globe scramble to find a way to end the COVID-19 pandemic.
Jonathan Saltzman can be reached at email@example.com