Medical experts have often expressed hope that a vaccine for the SARS_CoV_2 virus, which causes COVID-19, will be developed within the next 12 -18 months. What exactly goes into making vaccines that are both safe for humans and effectively provide a protective response to exposure to a virus?
“The very first round of questions that is usually asked by a regulatory body like the Federal Drug Administration, the FDA, is the safety of the product," said Bart Tarbet, a research associate professor with the Utah State University Antiviral Research Laboratory currently investigating the SARS_CoV_2 virus.
“So what we do here at USU, both with antiviral drugs and vaccines, is that we first evaluate these things in small animal models to show their safety and their efficacy," Tarbet said.
Tarbet explained that once the chemical compounds in the vaccine are shown to be safe, human testing can begin in phased trials, focused on outcomes of safety first, and effectiveness of the vaccine, once safety is demonstrated. A phase one clinical study usually looks at safety in healthy adults, followed by a phase two study that adds younger and older healthy people. Later trials will include those with underlying health conditions or children.
“Our children are precious to us. And so we don't want anything that's going to harm them. So they're often some of the last groups to be added to a clinical study until we have a lot of information and we're very confident that it will be safe,” Tarbet said.
During the clinical trials, once safety is demonstrated, researchers test for the onset of immunity– how soon is one protected after vaccination, and duration of immunity– how long will immunity last? Immunity for the SARS_CoV_2 virus is still not known. Immunity is typically measured either by antibodies in the bloodstream or by a cell-mediated response where T-cells and other cells clear the virus from the body.
“We would love to be able to evaluate a vaccine efficacy by an antibody titer in a blood sample, just because it's so simple to do," Tarbet said. "What can be a difficulty with a new virus like this or a new emerging disease is sometimes we don't know what the best type of immune response will give protection.”
Research into the earlier SARS_1 virus provides a jump-start to the timeline for SARS_CoV_2 vaccine according to Tarbet. But researchers are dealing with levels of complexity and many unknowns, conscious of the step-wise process that protects the public and ensures a safe, effective vaccine. Tarbet is acutely aware of the limitations of the process.
“I make animal models, pre-valuations of drugs and vaccines," Tarbet said. "And the mice that we buy are syngenetic, which is an interesting term, it means that they're almost like they're all twins. What that does for us is it eliminates variability in our animal studies, so we can use fewer animals and get a result. But that is not the nature of people – we’re outbred, in a sense. A mouse is not a man. Just levels of complexity. We do the very best we can. And try to right now we are just running, trying to get as much done as we can.”
