Flu viruses mutate extremely fast, and the only way to stop them to destroy their ability to evolve. Scientists may have found the secret to creating a universal flu vaccine using this theory.

According to a team of Princeton researchers, there are two crucial points making flu less severe once you've contracted it. Identifying this would greatly cut down the contagiosness of the virus and target the parts of the virus that are the most unchanging and the least adaptable.

The idea behind this is to not look at the constantly evolving part of the virus, but instead target something that's not changing. Current flu vaccines target hemagglutinin, or HA, which are proteins on the surface of the virus that attach to the host cells. If it can't attach to a host, then it will quickly perish. The problem here is that these proteins are extremely adaptable, and before you know it the virus strain has evlved a resistance to the vaccine.

The universal vaccine that's being designed now is made to ignore the hemagglutinin and go after other proteins inside the virus. These proteins are stable and they can't evolve under pressure in the same way that HA can which makes them vulnerable to longer lasting vaccines than the proteins on the surface.

This would reduce the severity of flu cases as well as reduce outbreaks of highly contagious new strains. According to researchers:

"We found that by putting the brakes on flu transmission, you could also put the brakes on flu evolution. Our model illustrates how we can control the flu this way, instead of simply reacting to it every few years. You can close schools and administer our current crop of vaccines and antiviral drugs as much as you want, but never realistically enough to stop transmission over any extended period of time. With the cross-protective vaccines, we may be able to finally throw a blanket on the transmission of all flu strains over the long term in a way that can impact the virus' evolution."