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A new study in monkeys suggests that a blood test could predict the effectiveness of a COVID-19 vaccine – and possibly speed up the clinical trials needed to get a vaccine effective for billions of people around the world.
The study, published Friday in Nature, reveals telltale blood markers that predict whether a monkey’s immune system is ready to clear out incoming coronaviruses.
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This finding gives hope that researchers will be able to look for the same markers in people who are vaccinated in clinical trials. If the markers are strong enough, they could reveal whether vaccines protect against COVID-19. And researchers would no longer have to wait for some of the trial volunteers to catch the disease, as they currently do.
“This will pave the way for much faster progress in the field of COVID vaccine,” said Dr. Dan Barouch, vaccine expert at Beth Israel Deaconess Medical Center in Boston and one of the researchers behind the new study. .
Last month brought the startling news that clinical trials of two new coronavirus vaccines, one from Moderna and the other from Pfizer and BioNTech, have shown efficacy rates of around 95%.
The strength of these two vaccines is, ironically, bad news for dozens of others in the early stages of development. Many of them will most likely need to be compared to the hardy pioneers rather than a placebo. Because this is a high statistical bar to cross, their trials will require significantly more volunteers, time and money.
“We would have to follow millions of people for a long time,” said Dr Nelson Michael, director of the Center for Infectious Diseases Research at the Walter Reed Army Institute of Research, where a protein-based vaccine is being prepared for clinical trials. . early 2021. “It’s just fantasy.”
For some small businesses, these comparison tests can be decisive factors. “You’re going to see a lot of dropouts,” said Dr. Gregory Poland, a vaccine expert at the Mayo Clinic.
This is a big deal, as Pfizer and Moderna will not have enough doses to administer to everyone in the United States, let alone the world. And the next wave of vaccines may be superior to the first in one way or another. They could cost a lot less, for example. Some may come in one dose instead of two and do not need freezing. Some may offer protection that lasts much longer.
“We would rather not have to revaccinate the world every one or two years,” Michael said.
The new monkey study offers a silver lining for these next-generation vaccines, suggesting that they could be tested not against older vaccines, but using a measure known as the “correlate of protection.”
“This is the holy grail of vaccine research,” Michael said.
Influenza vaccines are already tested this way. Each new flu season requires the design of a new flu vaccine, but researchers don’t have to do clinical trials comparing it to older versions. Instead, they just check to see if the new vaccine causes a person’s immune system to make enough of a certain type of influenza antibody. If so, researchers know that the vaccine adequately stimulates the immune system.
If scientists could find a correlate of protection against the coronavirus, they could follow the lead of the flu. “It’s a very plausible and achievable scenario,” said Dr. Anthony Fauci, director of the National Institutes of Allergy and Infectious Diseases.
A spokesperson for the Food and Drug Administration said that basing clinical trials on correlates of protection – if they are found to exist – “may be considered in the future.”
In their new study, Barouch and his colleagues found a correlate of protection in monkeys. They built the experience on their previous research showing that once monkeys recover from COVID-19, they can resist a second infection. Scientists took blood from these exposed animals and isolated a set of protective antibodies called IgG.
The researchers sought to find out if there was a level of IgG that reliably protected the monkeys from COVID-19. If the IgG antibodies produced by the vaccines were above this level, the vaccines could be found to be effective.
To find this line, the researchers gave the monkeys different doses of antibodies, then exposed them all to the coronavirus and observed how well they fight infection. In the monkeys with the lowest dose, the viruses multiplied as they would in an ordinary animal.
But the monkeys that received a medium dose produced much less virus. Some of them were able to completely eliminate viruses. At the highest dose, the monkeys were completely protected.
Until now, scientists have relied on circumstantial evidence suggesting that IgG antibodies are essential for clearing coronavirus infections. The new study puts this idea to the test and determines the threshold of IgG antibodies required to ward off infection.
“This is the first time, to my knowledge, that we actually prove that antibodies protect,” said Barouch. “Everything else is a statistical association.”
Experience has shown that a modest amount of IgG antibody has been shown to be sufficient. This could be encouraging news for vaccine developers, as even mediocre vaccines may be able to cross the threshold.
Researchers are now beginning to examine the results of clinical vaccine trials to see if a correlate of protection like that identified by Barouch and his colleagues in monkeys exists in humans. “The study bodes well for future studies on immune correlates,” said Holly Janes, a biostatistician at the Fred Hutchinson Cancer Institute in Seattle who was not involved in Barouch’s study.
Although these studies take a long time to produce solid results, Janes said preliminary clues made her optimistic.
“Emerging data suggests we might be pleasantly surprised,” she said.
This article originally appeared in The New York Times.
© 2020 The New York Times Company
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