The vaccine, engineered by pharmaceutical companies Pfizer and BioNTech, reported its vaccine is 90% effective against SARS-CoV-2, the virus that causes COVID-19.
Dr. Tony Moody, director of the Laboratory of B cell Immunotechnology at the Duke Human Vaccine Institute (DHVI), said he is excited about the vaccine, which uses a technology that has never before been utilized in a late-stage clinical trial.
"This is really the first time this has been deployed in this many people," Moody said. "It could be really game changing, to be quite honest."
But Moody has some lingering questions about the data involved in these preliminary results, and about the plausibility of distribution of this particular vaccine.
Why this vaccine is unique
Moody said giving the body a vaccine is like training in a martial art.
"You practice and practice and practice, so that when you get to the situation, you know how to deal with it," Moody said.
Vaccines train the body to make antibodies--molecules that latch onto markers on cells or pathogens and signal the body to respond, either by blocking the virus' ability to get into cells or by signaling attack cells to destroy it.
Typically, this process involves taking a whole pathogen--like a virus or bacteria--or part of the organism, then modifying it so it doesn't cause disease. In the case of the measles vaccine, for example, researchers use a form of the measles virus that does not cause infection, while the flu vaccine uses broken up pieces of flu viruses that won't make you sick.
However, Pfizer's vaccine moves a step backwards from these more traditional approaches. Instead of creating proteins identical to those that the body's antibody would respond to--a process that Moody says is difficult and labor intensive--Pfizer's vaccine inserts the instructions for making that protein into the body, where the body's own cells then manufacture the protein and trigger an antibody response.
Those instructions are on a molecule called messenger RNA (ribonucleic acid), which is a copy of an organism's genetic material that provides the instructions for creating proteins. Moody explained that this vaccine technique mimics the virus's activity inside the body, thus triggering the immune response in the same way.
"So what we're doing is we're sort of replicating a piece of that, but we're doing it in such a way that the body isn't, it's not possible to become infected by the virus," Moody said. "It's only there for a limited period of time. The body basically makes it, the immune system responds to it, and then it goes away."
But, he said, there are challenges to this method. Because the body is very good at recognizing--and destroying--foreign mRNAs, vaccine developers had to figure out how to disguise the molecule to get it into the body's cells.
"The last thing we want to do is give somebody a vaccine and then have their body react in a way that would trigger a bad response," Moody said.
Researchers developed a little bubble of fat to encase the mRNA--known as a lipid nanoparticle. However, these bubbles create a new problem for the vaccine--and one of Moody's biggest concerns for viable distribution of the product.
The cold problem
Moody said the lipid nanoparticles that encapsulate the mRNA are extremely temperature sensitive and must be kept very, very cold.
"They haven't figured out how to make them yet so that they would be stable just sitting on a shelf or being shipped across the country, you know, and hitting, you know, Death Valley desert temperatures," Moody said.
The vaccine has to be stored at -80 degrees Celsius. To put it in perspective, that's the temperature at which carbon dioxide--the gas people exhale--freezes solid (what we know as "dry ice").
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"You can't let them go outside that range," Moody said. "If they go outside that range, they stop working."
Pfizer is working on a distribution plan that involves using temperature-controlled trucks to transport the virus for up to 10 days, It can then be stored in a normal fridge or freezer for just a couple of days, or on dry ice for up to 15 days.
Moody said large medical institutions, like Duke and the University of North Carolina, have specialty freezers that maintain a temperature of -80 degrees Celsius. But, he added, this kind of equipment is in short supply--and can cost thousands of dollars.
And furthermore, he said he is concerned that fluctuations in temperatures--even by accident--could have dire repercussions.
"Think about when you go on vacation," Moody said. "You've got stuff in the freezer. You come back from vacation. How do you know that the freezer didn't die or that the power didn't go out for four days and everything in there is now rotten?"
Moody added that he is less concerned about facilities in urban centers having the necessary equipment and is more worried about rural areas not having the right infrastructure to keep the vaccine at that cold temperature.
"It's not an easy problem to solve, but thank goodness it's the right problem to have to solve," Moody said. "That's the cool part about this. For the first time in a while we've got what looks like a really, really good possible signal here."
He added that these distribution problems are surmountable with creative problem solving.
So what does 90% effective actually mean?
Moody said the initial data and the press surrounding the Pfizer announcement leave him with some questions.
"What are the data when they're saying 90% efficacy? How are they defining that exactly?" Moody said.
He explained that there are multiple ways to analyze the data from a clinical trial, and while all of those methods are technically correct, it does change how the results should be interpreted.
Moody also said key questions lie in whether the vaccine is effective at reducing all infections or just symptomatic infections, and whether it prevents an infected person from shedding the virus and spreading it to others.
Plus, Moody said a key question is whether the vaccine promotes long-lasting immunity.
"Does that 90% hold up six months from now, or does it wane? Is this a vaccine where people are going to have to get boosters?" he said.
Part of the issue, Moody explained, is that vaccines trigger an antibody response, but we don't know how long antibodies to SARS-CoV-2 last in the body. Recently, doctors have described cases in the U.S., Hong Kong and Europe in which a person became reinfected with COVID-19 after recovering from the illness.
However, Moody said there is evidence that Pfizer's vaccine--and others like it--are good at recruiting a specific kind of cell in the body that is programmed to kill viruses and cells infected with viruses, known as a T-cell. T-cells hang around the body longer than antibodies, and therefore might present an opportunity for longer-lasting immunity.
The marathon continues
Still, Moody added that a key part of the story is that this vaccine is just the first to get to this benchmark.
"We're talking about the first generation of vaccines," Moody said. "Just because we get a successful vaccine doesn't mean that the research stops. We need to keep studying. We need to keep looking. We need to make sure that whatever we're doing is the best, and we probably can do better."
Moody said he's hopeful that some of the other vaccine candidates--including those that use a more traditional approach to the technology--will also have positive results. And if a vaccine receives authorization or approval from the Food and Drug Administration, he said the scientific community will continue to optimize those vaccines.
"I'm absolutely thrilled that we've got something that is this good right now, but you know, maybe we can get to 95, or maybe we can get a vaccine that uses a lower dose, or maybe has a vaccine that doesn't have the cold chain requirement," Moody said.
Pfizer hopes to produce 50 million doses of the vaccine this year. The company will send its full Phase 3 data to a scientific journal for peer-review, and will seek emergency use authorization from the Food and Drug Administration once it meets the necessary safety benchmarks.