An influenza vaccine that protects against all pandemic strains of the infection could be developed after a volunteer in a medical study had an unusual reaction to the flu virus.
Scientists analyzed a group of people who had either been infected with or vaccinated against the flu, reports The Guardian.
Tests revealed one participant who produced a "super-antibody" that could fight off every strain of influenza A, the virus responsible for mass outbreaks of the illness.
The person produced too little of the super-antibody to make them immune to the flu, but scientists believe they can boost its effect, and use it to create vaccines against the virus.
In preliminary tests, researchers showed that injecting mice and ferrets with the super-antibody protected the animals against doses of influenza that would normally be lethal.
Antonio Lanzavecchia is the director of the Institute for Research in Biomedicine in Bellinzone, Switzerland.
"What we can do now is mass-produce this super-antibody and give it as a therapeutic,” he told The Guardian.
"This could be developed to treat any influenza A infection and prevent any possible new pandemic that will come out,” Lanzavecchia said.
“We expect it will block not only the strains that circulate in humans but also those that are present in animals," he added.
Steve Gamblin is a co-author of the study and a structural biologist at the Medical Research Council's National Institute for Medical Research in north London.
He said that, if proven to work safely, the antibody might be given directly to hospital staff and other frontline workers to protect them against flu pandemics.
In the longer term, scientists hope to create a vaccine that makes the body launch its own devastating attack on influenza by producing a surge of super-antibodies.
Traditional flu vaccines make the body produce antibodies that target proteins called haemagglutinins on the surface of the influenza virus.
But these antibodies focus their attack on the tips of the proteins, which change as the virus mutates.
Because the virus evolves with such rapidity, flu vaccines have to be reformulated every season.
The super-antibody is different because it binds to a part of the stem of the haemagglutinin that is shared by all influenza A strains and appears not to mutate.
Thus, Lanzavecchia calls it the virus' "Achilles heel,” reports The Guardian.
A universal flu vaccine could transform public health by making seasonal jabs a thing of the past and reducing the often-devastating impact of fresh outbreaks.
This includes outbreaks that spread from animals to humans, such as the recent strain of swine flu.
The groundbreaking study appears in the journal Science.
