The emerging class of long-lasting universal flu vaccines could do more than shield infections through an annual single flu shot, according to researchers at Princeton University.

In a new study published in the Proceedings of the National Academy of Sciences, researchers observed for the first time that a universal vaccine could allow for a more wide-scale prevention of the flu by restraining the ability of the influenza virus to spread and mutate.

Touted as cross-protective vaccines, these are at various stages of development across labs worldwide. Some of the vaccine variants are under clinical trial and are seen as the potential target drug for their effectiveness against several flu strains.

According to experts, the new study is the first attempt at understanding the population consequences of the next generation of vaccines as regards the epidemiology and evolutionary impact on the virus.

The research team developed a computational model enlisting parameters that could enable control of the flu virus during seasonal outbreaks as well as for the emerging highly contagious new strains.

They analyzed data from the latest vaccine clinical trials that were based on the best models of influenza virus evolution and epidemiology. The information was translated into how the new universal vaccine would actually contain flu and other infections within certain vulnerable population domains.

The study report emphasized that these cross-protective universal vaccines could even improve the efficacy of the current vaccines targeted to fight specific flu strains.

The study expects that the new vaccines might contain the spread of the flu viruses by destroying their ability to evolve or mutate and thus bring down the severity of the influenza bout.

Because the flu quickly evolves to escape host immunity, current vaccines tend to be prioritized for inoculating specific high-risk groups such as asthma sufferers and the elderly every year, said lead author Nimalan Arinaminpathy, from Princeton's Department of Ecology and Evolutionary Biology.

He explained that the current vaccine programs focus on clinical protection but the aim is to control the spread of the virus by nipping it in the evolutionary stages. Our model provides a strong conceptual basis as to how and why the 'universal' vaccines would achieve that, added Arinaminpathy.

Arinaminpathy and his colleagues developed their model using a prototype of the universal vaccine. He explained in his paper that the current genre of flu vaccines are developed against a particular virus strain based on WHO's (World Health Organization) assessment of a dominant virus for a particular flu season. Likewise, immunization programs are then developed to focus on protecting vulnerable people from the said virus strains.

According to Arinaminpathy, this approach is not viable for long-term or widespread immunity. His explanation is based on the fact that the flu virus is constantly evolving, and therefore there is a need to update the efficacy of the vaccines with each passing year.

The mechanism studied was based on new universal vaccines that are designed to ignore the hemagglutinin protein or HA and go after other proteins inside the virus by impairing them for longer periods or completely wiping them out.

The current available vaccines target HA which are found on the surface of the virus via which they attach to the host cells. Although, this is the most viable protein to attack before they can harm the human or host cells, these proteins can adapt and develop resistance to the vaccine.

The new approach of the universal vaccines is to ignore this hemagglutinin protein and go after other proteins inside the virus which is seen as a more potent mechanism. This makes the virus more vulnerable to the longer-lasting vaccines than the ones that merely target viral proteins on the surface.

An advantage is that the new universal vaccines do not attack the hemagglutinin protein thus keeping it intact. Although this makes the virus viable to infect people, its internal supply chain gets disrupted, thereby reducing the severity of the infection.

To combat the problem of the flu pandemic, researchers found that the new vaccines could help in averting a large-scale pandemic even when a small population receives vaccination. They wrote that the vaccine would raise herd immunity, wherein even unvaccinated individuals would be protected because many people around them were immune.

The researchers also explored how cross-protective vaccines could help against predominant strains that cause flu epidemics every winter. A flu pandemic -- the sudden and rapid spread of a new, highly contagious strain -- is difficult to predict and typically impossible to control through vaccination alone, Arinaminpathy said.

He explained that universal vaccines act on virus targets that are relatively constant across all types of flu, including the pandemic flu. To test how the vaccine would affect the flu virus, the researchers worked on their model based on the two prevailing theories of flu evolution.

We found that by putting the brakes on flu transmission, you could also put the brakes on flu evolution, Arinaminpathy said. 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, he said. 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, he added.