Researchers are working to find a better, long-lasting flu shot that doesn’t need to be given every year, but say they first need to better understand both the virus and how the immune system responds to it. 

Since a flu virus makes some small changes to its surface proteins every year, the immune system may not recognize it and respond. That’s why flu shots are offered every year — to target the parts of the virus that is constantly changing.

Ideally, flu vaccines would work like childhood vaccines that offer protection for decades. To that end, researchers around the world are also studying how to make a "universal" vaccine that targets the parts of the flu virus that don’t change.   

"We’re trying to tweak the immune response to sort of one-up the virus," said Maureen McGargill, an immunologist at St. Jude Children’s Hospital in Memphis, Tenn. "But the structure of the virus and the immune response to it has made it very challenging."

In mice, McGargill is testing a potential vaccine against two bird flu viruses, H5N1 and H7N9, as well as the H1N1 that caused a pandemic in 2009 and is now circulating as seasonal flu.   

McGargill is testing how tweaking the immune response creates different antibodies that offer broader protection than seasonal flu vaccines.  

Other labs around the world, including the National Microbiology Laboratory in Winnipeg, are also trying different strategies to target the common portion of flu viruses to come up with a better flu vaccine. 

Flu vaccine

The race is on for a universal flu shot that doesn't have to be given every year, but it could take 10 to 20 years for that to happen. (CBC)

In the U.K. last year, researchers at Imperial College London discovered that blood samples collected from volunteers during the 2009 H1N1 pandemic showed those who didn’t fall seriously ill had more virus-killing immune cells in their blood. 

The British researchers believe that if they can get the body to produce more of these specific immune cells, called CD8 T cells, then people could be protected from flu symptoms — a different approach to try to achieve a better flu vaccine.  

Dr. Danuta Skowronski of the B.C. Centers for Disease Control in Vancouver is a strong supporter of efforts to create a universal flu vaccine.  

"Influenza vaccine is the only immunization that you have to give on an annual basis," Skowronski said.  

Part of the interest in pursuing an improved flu vaccine comes from recent studies that showed the flu vaccine’s effectiveness is in the 50 to 60 per cent range, compared with 90 per cent for other vaccines, she said.  

Skowronski points to the example of the polio vaccine effort that brought together intelligence and resources with concrete timelines as what’s still needed to develop a universal flu vaccine.

"We need that kind of structure applied to the pursuit of improved influenza vaccine options."

If a better, longer-lasting flu vaccine is developed, it could also reduce the huge toll of human suffering from flu and the nearly billion dollars over five years that it costs to buy and administer seasonal flu vaccines, she added. 

Scientists estimate it could take another 10 to 20 years before a universal flu vaccine is available.  

With files from CBC's Kas Roussy and Amina Zafar