Gary Nabel, director of the Vaccine Research Center at the National Institutes of Health, has also been investigating the stem antibody approach. “It doesn’t look like the vaccine is highly potent in its current form, but I have no doubt that [Palese] will keep working on it and get it to work more potently,” he says. “Whether it’s going to be sufficient is really a question. His data suggest that it’s not enough to prevent infection in all subgroups, although it delays it.”
Even finding a vaccine that could prevent all infections from a single subgroup, however, could be a boon to researchers and patients alike. “If we’re lucky enough to find one broadly neutralizing antibody that protects against all strains, that would be wonderful,” Nabel says. But the right combination of less-broadly neutralizing antibodies could work, too.
Given the promising results, Palese and colleagues plan to move to animal models that are more reflective of success in humans. “It’s much easier to protect the mouse against influenza than it is to protect the human,” Palese says.
Because the vaccine can’t protect against infection–just against propagation of the virus once it has already infected some cells–the current version may not provide a great enough defense for people with weakened immune systems. Nor could it provide full protection against all flu strains. But combined with current vaccines, it could help provide a first-line or second-line defense.
“This could potentially be used in the future as a supplement to the current vaccine, because it has such broad cross-reactivity, but it’s going to be difficult to get rid of the current vaccine, because it’s so effective from preventing the virus from infecting,” says Terrence Tumpey, an influenza microbiologist at the Centers for Disease Control and Prevention in Atlanta. “Scientists for years have been trying to find an approach for a universal vaccine. I’m really excited about the prospect of this type of work, although it’s still in the early stages.”