Somewhere in the order of 50 to 60 per cent, in healthy adults, is more accurate, the newer studies suggest. Efficacy rates are lower in the elderly or people in poor health.
The report suggests that the higher numbers came from old studies done on vaccines that were not formulated the way current shots are. It also suggests that the belief that universal vaccination for flu would be useful and desirable, rather than solid scientific evidence, was what drove decisions to recommend flu shots for all in the U.S. (The study did not look at decisions made in Canada or elsewhere.)
Even the vaccine used in the U.S. during the 2009 pandemic — where there was a perfect match between the virus in the vaccine and the strain infecting people — didn't offer better protection. Studies cited in the report pegged the U.S. vaccine's effectiveness at 56 per cent.
Dr. Danuta Skowronski, an influenza expert at the B.C. Centre for Disease Control, is involved in flu vaccine efficacy studies that have been conducted annually in Canada since 2004. She said the findings of those studies support the arguments made in the CIDRAP report.
"Over that period, seldom has the seasonal vaccine effectiveness exceeded 60 per cent," Skowronski said.
The world spends enormous sums trying to vaccinate people against influenza every year. In Canada alone, Skowronski said, spending on flu vaccine programs likely exceed $100 million per year.
"We need a better vaccine," she said. "And investing in improved vaccine options may be more rewarding than expanding the use of the current vaccine to greater segments of the population."
A key argument of the report is the fact that the current vaccine that offers moderate protection is actually getting in the way of developing long-lasting flu vaccines that offer more effective protection — vaccines, for example, that might require a shot every five or 10 years. Currently flu shots are reformulated every year to try to keep up with the evolution of flu viruses.
"I don't want to oversimplify this dilemma of what do you do now?" said Dr. John Treanor, an expert in flu vaccines and chief of the infectious diseases division at the University of Rochester (N.Y.) Medical Center.
"How do you at the one time promote the vaccine that you have and at the same time create space to make new vaccines? I think that's a very difficult thing to do."
In recent years pharmaceutical companies — spurred in large part by massive funding from the U.S. government — have been working on ways to improve existing vaccines. But tweaking the current vaccines won't solve the problem, the report says, insisting that what is needed are vaccines that target different parts of the flu virus than the current ones do.
The enormous cost of developing such vaccines means the only way they will come into existence is if governments support the work, the report says, noting that producing a single new flu vaccine could take 15 years of work and cost a company upwards of US$1 billion.
It called on the U.S. government to play the lead role in pushing this agenda, saying the World Health Organization is not in a position to do so.
And there is little incentive for industry to take the risk to develop wholly new flu vaccine approaches, the report says.
Even though a flu shot is a relatively inexpensive vaccine, manufacturers sell hundreds of millions of doses of them a year. In fact, the report notes that the global market for flu vaccine is estimated at US$2.8 billion — a decent chunk of the estimated US$20 billion annual market for all vaccines combined.
Treanor said in his estimation, a major advance in flu vaccines is not around the corner.
"I think we're very far away from the game-changing vaccine right now."