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What's in this vial changes from year to year, but the process of creating the flu vaccine remains pretty constant.
Flu shots are safe, cheap and pretty much universally recommended.
But how well do they really protect us from getting sick?
The most comprehensive review to date, just published online by The Lancet, suggests that flu vaccines aren't as effective as many of us have thought.
An analysis of 31 published studies conducted since 1998 found that vaccination against influenza is moderately effective in keeping healthy adults healthy. But evidence of protection was lacking for some of the groups who need it the most, including adults 65 and older.
"We found a number of differences in how influenza vaccine has performed in different populations of people," Michael Osterholm, the study's lead author told Shots. Osterholm heads the Center for Infectious Disease Research and Policy at the University of Minnesota.
Between 3,000 and 49,000 Americans die from the flu in an average year, a number that fluctuates so much in part because of the unpredictable nature of the disease. Flu is a unique public health problem, because it can be both seasonal and pandemic, and its severity varies from cycle to cycle.
Due to that variation, the exact cocktail in the syringe (or spritz of immunizing nasal mist) has to be updated annually, and people have to get new shots. "It's clear that what we really need is to develop new and better vaccines," Osterholm said. The ultimate goal would be a universal vaccine that's effective against all strains of flu.
But that's not going to be an easy task. At the moment, Osterholm said, there are "major barriers to new vaccines entering the market, particularly vaccines that are novel."
And those barriers have to change without the current market for flu vaccinations dropping, because the medical recommendation to get them will remain pretty universal.
"Moderate effectiveness is still effective," Dr. Andrew Pavia, an infectious diseases specialist at the University of Utah, told Shots.
He compared the influenza vaccine to seatbelts, which are accepted as an important safety measure even though they can't save lives in every car crash. "If there's a cheap, simple, safe and effective measure that will get you pretty good protection, why would you wait until there's perfect protection?" he asked.
But that same line of thinking is part of what's hurting the chances that a better vaccine will be developed. From a business perspective, it makes little sense to pour money into a new product for which there appears to be no demand, Osterholm said.
The final paragraphs of the paper highlight the need for more research and development, fewer regulatory barriers for licensing new flu vaccines, and financial models that favor the purchase of more expensive vaccines if they prove more effective.
In short, the study concludes that the effort to develop a better flu vaccine will require an active partnership between industry and government. "Pursuit of this goal now will save lives every year and when the next influenza pandemic occurs," the authors conclude. "In the meantime, we should maintain public support for present vaccines that are the best intervention available for seasonal influenza."