Yearly flu shots could be a relic in less than a decade, as scientists say they are on the verge of developing a universal vaccine capable of treating all strains of seasonal influenza.

Flu viruses are able to mutate rapidly in response to new vaccinations, something that has forced doctors to develop new treatments for every flu season. But Dr. Francis Collins, head of the National Institutes of Health, told USA Today that he was "guardedly optimistic" about the prospects of developing an all-encompassing vaccine within the next five years.

"There are parts [of the virus] that don't change," Collins said. "If you designed a vaccine to go after the constant part of the virus, you'd be protected against all strains."

If true, the predictions would represent a significant breakthrough for a vaccine that has long eluded scientists and that "seemed completely out of reach only a few years ago," Collins said.

That optimism was bolstered by a study conducted by a team of scientists in Britain and Switzerland who found that a flu-resistant patient produced a unique antibody that appeared able to attack disparate strains of the influenza A virus, which causes numerous flu cases each year. When researchers injected the antibody into mice and ferrets, the animals also became immune to influenza A.

The flu represents one of the leading preventable causes of death, killing between 250,000 to 500,000 lives yearly, of which 36,000 are in the U.S., and hospitalizing about 200,000. A universal vaccine would likely incorporate antibodies that are able to recognize the recurring parts of the flu virus.

The National Institute of Allergy and Infectious Diseases has been hard at work testing various vaccines on mice, ferrets and monkeys, and researchers have been able to produce antibodies that attack a variety of different influenza strains, according to the organization's website.

There are various different types of the flu. The seasonal flu occurs annually and affects between 5 and 20 percent of Americans. Particularly virulent strains of the flu -- that is, those with the capacity to rapidly infect a large number of people -- are subsumed under the category of pandemic flu, which includes the H1N1 virus. A universal vaccine could help halt a pandemic before it begins.

"As we saw with the 2009 pandemic, a comparatively mild strain of influenza can place a significant burden on emergency services," John Skehel of Britain's National Institute for Medical Research told Reuters. "Having a universal treatment which can be given in emergency circumstances would be an invaluable asset."