New four-in-one flu shot may provide protection from all influenza viruses

A vaccine combining ancestral genes from four major influenza strains appears to provide broad protection against the dangerous ailment, a study conducted on mice has found.

Mice protected by the unconventional vaccine survived exposure to lethal doses of seven of nine widely divergent influenza viruses, according to researchers from the University of Nebraska-Lincoln in the US.

Those that received higher doses of the vaccine did not even get sick. In contrast, mice that received traditional flu shots or nasal sprays all sickened and died when exposed to the same viruses.

The deadly pathogens were able to evade the immune responses triggered by the traditional vaccines, researchers found.

While it is too soon to say the approach could be successfully used in humans, it appears to be a promising avenue towards a universal flu shot, said Eric Weaver, an assistant professor at the University of Nebraska-Lincoln.

The study is the first to report on whether a universal flu shot could be created by using a combination of multiple genes shared at the ancestral level by flu strains circulating today, he said.

"The ultimate goal is to be able to vaccinate once and provide lifelong protection," said Weaver, who led the study published in the journal Scientific Reports.

The conventional influenza vaccine platform uses weakened or dead versions of the influenza virus to stimulate immunity against hemagglutinin (HA), a spike-shaped protein that extends from the surface of the virus and attacks cells.

Conventional vaccines have been shown to be less than 60 per cent effective when they are successfully matched to the currently circulating strain. They are far less effective when mismatched, researchers said.

"An ideal influenza vaccine would be inexpensive, provide long-lasting immunity, require few immunisations and would work against all variants of the virus," Weaver said.