The race to develop a SARS-CoV-2 vaccine is unlike any other global research and development effort in modern medicine.
According to Paul A. Offit, MD, there are now 120 Investigational New Drug applications to the Food and Drug Administration for these vaccines, and researchers at more than 70 companies across the globe are interested in making a vaccine. The Biomedical Advanced Research and Development Authority (BARDA) has awarded $2.5 billion to five different pharmaceutical companies to make a vaccine.
“The good news is that the new coronavirus is relatively stable,” Dr. Offit, director of the Vaccine Education Center at the Children’s Hospital of Philadelphia, said during the virtual Pediatric Dermatology 2020: Best Practices and Innovations Conference. “Although it is a single-stranded RNA virus, it does mutate to some extent, but it doesn’t look like it’s going to mutate away from the vaccine. So, this is not going to be like influenza virus, where you must give a vaccine every year. I think we can make a vaccine that will last for several years. And we know the protein we’re interested in. We’re interested in antibodies directed against the spike glycoprotein, which is abundantly present on the surface of the virus. We know that if we make an antibody response to that protein, we can therefore prevent infection.”
Some research groups are interested in developing a whole, killed virus like those used in the inactivated polio vaccine, and vaccines for hepatitis A virus and rabies, said Dr. Offit, who is a member of Accelerating COVID-19 Technical Innovations And Vaccines, a public-private partnership formed by the National Institutes of Health. Other groups are interested in making a live-attenuated vaccine like those for measles, mumps, and rubella. “Some are interested in using a vectored vaccine, where you take a virus that is relatively weak and doesn’t cause disease in people, like vesicular stomatitis virus, and then clone into that the gene that codes for this coronavirus spike protein, which is the way that we made the Ebola virus vaccine,” Dr. Offit said. “Those approaches have all been used before, with success.”
Novel approaches are also being employed to make this vaccine, including using a replication-defective adenovirus. “That means that the virus can’t reproduce itself, but it can make proteins,” he explained. “There are some proteins that are made, but most aren’t. Therefore, the virus can’t reproduce itself. We’ll see whether or not that [approach] works, but it’s never been used before.”
Another approach is to inject messenger RNA that codes for the coronavirus spike protein, where that genetic material is translated into the spike protein. The other platform being evaluated is a DNA vaccine, in which “you give DNA which is coded for that spike protein, which is transcribed to messenger RNA and then is translated to other proteins.”
Typical vaccine development involves animal models to prove the concept, dose-ranging studies in humans, and progressively larger safety and immunogenicity studies in hundreds of thousands of people. Next come phase 3 studies, “where the proof is in the pudding,” he said. “These are large, prospective placebo-controlled trials to prove that the vaccine is safe. This is the only way whether you can prove or not a vaccine is effective.”
“Some companies may branch out on their own and do smaller studies than that,” he said. “We’ll see how this plays out. Keep your eyes open for that, because you really want to make sure you have a fairly large phase 3 trial. That’s the best way to show whether something works and whether it’s safe.”
The tried and true vaccines that emerge from the effort will not be FDA-licensed products. Rather, they will be approved products under the Emergency Use Authorization program. “Ever since the 1950s, every vaccine that has been used in the U.S. has been under the auspices of FDA licensure,” said Dr. Offit, who is also professor of pediatrics and the Maurice R. Hilleman professor of vaccinology at the University of Pennsylvania, Philadelphia. “That’s not going to be true here. The FDA is involved every step of the way but here they have a somewhat lighter touch.”
A few candidate vaccines are being mass-produced at risk, “meaning they’re being produced not knowing whether these vaccines are safe and effective yet or not,” he said. “But when they’re shown in a phase 3 trial to be safe and effective, you will have already produced it, and then it’s much easier to roll it out to the general public the minute you’ve shown that it works. This is what we did for the polio vaccine back in the 1950s. We mass-produced that vaccine at risk.”
Dr. Offit emphasized the importance of managing expectations once a COVID-19 vaccine gets approved for use. “Regarding safety, these vaccines will be tested in tens of thousands of people, not tens of millions of people, so although you can disprove a relatively uncommon side effect preapproval, you’re not going to disprove a rare side effect preapproval. You’re only going to know that post approval. I think we need to make people aware of that and to let them know that through groups like the Vaccine Safety Datalink, we’re going to be monitoring these vaccines once they’re approved.”
Regarding efficacy, he continued, “we’re not going know about the rates of immunity initially; we’re only going to know about that after the vaccine [has been administered]. My guess is the protection is going to be short lived and incomplete. By short lived, I mean that protection would last for years but not decades. By incomplete, I mean that protection will be against moderate to severe disease, which is fine. You don’t need protection against all of the disease; it’s hard to do that with respiratory viruses. That means you can keep people out of the hospital, and you can keep them from dying. That’s the main goal.”
Dr. Offit closed his remarks by noting that much is at stake in this effort to develop a vaccine so quickly and that it “could go one of two ways. We could find that the vaccine is a lifesaver, and [that] we can finally end this awful pandemic. Or, if we cut corners and don’t prove that the vaccines are safe and effective as we should before they’re released, we could shake what is a fragile vaccine confidence in this country. Hopefully, it doesn’t play out that way.”