The race to develop a COVID-19 vaccine is on, as scientists work as quickly as they can to find a way to prevent the disease that has sickened more 4.4 million people and killed more than 300,000 worldwide.
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On Friday, Dr. Francis Collins, the head of the National Institutes of Health, said the agency is planning to begin large-scale testing of several of the most promising vaccine candidates this summer. Despite such efforts, and despite statements from President Donald Trump this week, a vaccine most likely won't be ready by the end of the year.
However, progress has been made: Scientists at the University of Oxford posted the results of a small study conducted in rhesus macaques monkeys to the preprint server bioRxiv. The study found that the experimental vaccine successfully blocked the coronavirus in the monkeys, which are considered to be good proxies for how drugs could work in people because the monkeys share a majority of their genes with humans. Clinical trials with the Oxford vaccine are ongoing in humans.
For more on vaccine progress, NBC News spoke with Dr. Gregory Poland, director of the Mayo Clinic's Vaccine Research Group. His team's coronavirus vaccine is in the early, preclinical stages of development.
The conversation has been lightly edited for length and clarity.
NBC News: People are placing a tremendous amount of hope in a vaccine for COVID-19, an illness that in just over four months has infected millions worldwide and killed many thousands. From where you sit, is there evidence this virus could be prevented by a vaccine? Is it even feasible?
Poland: Definitely feasible. There's nothing I see or know that would lead me to say that we can't make a vaccine against this. The question of what kind of vaccine with what sort of effectiveness and what duration is another subject, but I think it is a key strategy in terms of developing population-level immunity.
NBC News: Dr. Francis Collins, director of the NIH, said that even though it's a "stretch goal," his team is attempting to have hundreds of millions of vaccine doses available by January. What's your reaction?
Poland: It is, as he admits, a gigantic stretch goal. What happens if there's a better vaccine candidate doesn’t come until July, August, and wouldn’t get included [in the summer's research trials]?
NBC News: What kind of timeline do you think is reasonable? Some have even said we could have one by this fall.
Poland: No, we will not. We are not going to have a vaccine this fall that has been adequately safety-vetted. Are we going to have one by the winter? Highly unlikely. The only way that can happen is if we develop new pathways and accept new, unknown risks to get there.
We typically think of vaccine development [timelines] of seven, 10, 20 years. The childhood varicella [chickenpox] vaccine took 20 years. The shortest that's ever occurred was the Ebola vaccine in about four years.
Anything shorter than four years has never been done in the U.S. So, anything we do shorter than that entails as yet unknown risks. And you have to frame this in the context of a highly vaccine-skeptical society that we live in. Already, the anti-vaxxers have geared up. I do a radio show, and people call in to say, "Doc, I talked to 10 of my friends, and eight of them already said 'no way am I taking this vaccine.'"
NBC News: Meaning scientists have to get this right, correct? What are the potential risks of moving too quickly?
Poland: First is the unknown. There is still a lot we as scientists are learning about this virus. Our total experience with this virus is 17 weeks long in the U.S. We know nothing about midterm and long-term effects. Nothing. Zero.
There is a fundamental tension between speed and how much we know about safety. There's a possibility that there will be a side effect or a syndrome of side effects that we don't yet suspect and don't yet know about.
Then there is the risk of antibody-enhanced disease if the antibody generated by the vaccine is not correct or optimal. It can actually predispose you to worse disease, if you got exposed to the wild virus.
Now the other thing is we don't yet know a correlative protection. So the fact that we give somebody a vaccine, and we're able to measure an antibody response, we don't know what level of antibody is protective. We don't know how that antibody might decay over time.
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NBC News: There are several candidates for COVID-19 vaccines. Do any stick out in your mind as most promising?
Poland: The one most ahead is the Moderna vaccine, a messenger RNA vaccine, a platform that's never been licensed in the U.S. The next closest would be the Oxford. And that's because of a peculiarity of their country [the U.K.] granting them the ability to almost immediately go into phase two studies, which wouldn't happen here. After that would probably be the Inovio, which is a DNA platform, which again, has never been licensed.
If the virus mutates in certain ways, it could render the vaccine less, or even noneffective. The poster child for that would be influenza vaccines. We have to reinvent the influenza vaccine every year.
Now, coronaviruses are a lot lower in terms of mutation rate, but that doesn't mean it isn't going to occur, particularly in another unusual scenario we face, which is likely to be an unprecedented amount of disease in the Southern Hemisphere as they get into their winter. The more times the virus passes through humans, the greater the accumulation of mutations.
NBC News: What kind of evidence do these vaccine manufacturers need to show to make you sit back and say. "Wow, this is a game changer?"
Poland: Do nonhuman primate studies and show me in a large enough number of animals that you were able to prevent infection, that you were able to identify a correlate of protection, and that there was no immunopathology upon deliberate exposure to the virus.
Once you have that, then go into phase one, phase two and phase three studies [of humans]. When you try to shortcut that process, you run the risk of side effects that you don't anticipate.
Ultimately, I think there will be more than one type of vaccine, and anything we come out with would be version 1.0. There will be further refinements almost assuredly. It's very hard to say, "We're going to get up to the plate, swing the bat, and our first one is a grand slam." It's possible, but it's unlikely.