Loïc Venance, a molecular geneticist at CRANN in Cambridge, England, tested the vaccine in a human rodent model. “It’s slightly more complicated in terms of genetically modifying the most virulent viruses, but we have found that it’s a whole new way of building a robust gene drive that can target individual pathways,” he says.
So far, the virus-based approach has demonstrated a 95 percent kill rate against SARS coronavirus. In the future, Venance hopes to get a wider group of people vaccinated, probably with an adjuvant to make it more potent. (Some scientists are concerned that gaining knowledge of how the current virus might evolve could let pandemics go undetected, so there’s still debate over this approach, though the vaccines seem to cut out the trouble that comes with side effects.) It could work for several viruses, he adds, “not just for one.”
Venance also thinks they can leverage this approach to develop a vaccine for polio, which has been eradicated in developed countries. “For the first time, we have the potential to target specific critical pathways of evolution and prevent its spread,” he says.
But less vulnerable viruses that normally evade vaccination, such as avian influenza, are also good candidates. “The way the bird flu works, it’s very efficiently evolved,” Venance says. Many viruses adapt to become transmissible from person to person, but viruses can also recombine, adding a more dangerous mutation. Because viruses typically evolve slowly, it might take decades before the human population as a whole is vaccinated. This could mean a resurgence of bird flu in hot spots where people aren’t vaccinated.
Prof. Anita Galach, head of epidemiology at Imperial College London, says two years into the H5N1 bird flu outbreak in Thailand she’s not quite ready to see if a new vaccine is a good idea for humans. “The faster we can figure out exactly how we want to protect, the more certain we are that there’s no likelihood of a major pandemic,” she says. “I have the feeling we are getting closer.” If it’s not a safe enough vaccine, she says, she worries the world will have less immunity to a new pandemic.
Though the shot doesn’t rely on a virus like SARS, it nevertheless took longer to hit the right strategy. “There’s no magic bullet,” says Galach. “This is going to have to be an iterative process, iterative across many groups over many years.”
Venance says even at this early stage the virus-based approach can’t guarantee immunity. “We have a long way to go to have this approach be useful for humans,” he says. And both Venance and Galach agree that the vaccine has only real value when it’s tested with an adjuvant, so that it makes sure every person who gets it will be immune and contagious if that next major pandemic hits.