The only thing that is spreading faster than the flu these days seems to be this question: Did you get a flu shot this season?
The question matters to the 40 percent of Americans who get the shot each year, and to the $2 billion industry that has been built around seasonal flu vaccination. And it matters to the U.S. government, the world's single largest buyer of flu vaccines.
Influenza's origin stories are unknown, but it grabbed the world's attention in 1918 during a worldwide pandemic that killed 20 million to 50 million people. The U.S. Army was concerned about a repeat of the great influenza pandemic during the World War II. That led to the first attempts to develop a flu vaccine. Seventy years on, the seasonal flu vaccines that are available today are largely similar to the ones developed in the 1940s.
So, how good are they? A report published in December by scientists at the Center for Infectious Disease Research and Policy, University of Minnesota, says the flu vaccine's effectiveness is moderate at best.
"It is an over-promotion," Nicholas Kelly, a researcher for the center, said. "There hasn't been a need to make a better vaccine because public health has been saying it works."
The outcome of the study that causes the most concern is that the vaccine had little or no effect on those 65 years or older, a segment of the population that accounts for 90 percent of flu-related deaths.
The roots of mass vaccination as a public health strategy can be traced back to the aftermath of the 1957 pandemic. Its effectiveness, however, has never been scientifically tested.
"In all these years, no link has been established between vaccination and mortality," said Tom Jefferson, a researcher with the Cochrane Collaboration. "The [Center for Disease Control] is making policy based on weak evidence and it is refusing to answer questions."
The Cochrane Collaboration has undertaken several meta-analyses - studies of studies. Jefferson said the flu vaccine works like a placebo in children less than two years of age and had limited effectiveness among healthy adults.
"There is no evidence that vaccines can prevent deaths or prevent person-to-person spread of infection," he added.
Seasonal vaccination exists just to satisfy an "industry," according to Jefferson. He points to companies such as GlaxoSmithKline recording a 60 percent increase in profits when the influenza threat levels were elevated during the 2009 Swine Flu scare.
But public health experts say the vaccine is definitely better than nothing. "Does it work as well as the measles vaccine? No, and it's not likely to. But the vaccine works," said Joseph Bresee, chief of epidemiology and prevention in the CDC's influenza division.
The question then really is whether the benefits are proportional to the costs incurred by U.S. tax payers each year. But here's the catch - influenza vaccines target only particular flu strains, which are categorized as A, B and C based on their protein composition. The strains that go into the vaccine are determined by the World Health Organization's worldwide network of flu monitoring stations in 72 countries. The three most dominant strains go into the vaccine each year. Most people who get sick during the winter suffer from "flu-like" illnesses that could be caused by an estimated 200 different types of pathogens.
"Much of the current system is based on models and guesses," said Jefferson.
Bresee on the other hand says vaccination is essential for a disease with such a huge public health relevance. "Flu is a complex disease. Immune response and strains do vary each year. But asking seniors not to have the flu vaccine is reckless."
Caught between these claims and counterclaims are the hapless public each year.
Influenza gained its name from the root 'Influentia', which literally means influence - a throwback to the time when it was believed to be caused due to the influence of the moon and stars. Science has definitely progressed since then. But it seems, not by too much.