Selecting the right vaccine to produce each flu season involves year-round surveillance from 142 national influenza centers based in more than 100 countries, according to the CDC. The World Health Organization gathers leaders once in the Southern Hemisphere and again in the Northern Hemisphere to comprehensively track the virus. Then, the WHO convenes in February to identify the dominant virus strain.
The U.S. Food and Drug Administration next decides which flu strains will be used to make vaccines sold in the U.S. The seven drugmakers contracted with the government can then begin development to get the vials to doctors' offices by early October.
It's a 70-year-old process that has proven to be safe and effective but very time-consuming. Last year's mutation is estimated to have happened about three months into the production process. Those situations highlight where the problems lie.
“We're committing to which flu strains we're going to make vaccines for a year in advance of when flu season hits,” said Dr. Christopher Gill, associate professor of global health at Boston University School of Public Health. “So it's always a guess.”
The CDC admits that virus mutation poses a challenge. The agency says that's when it emphasizes other preventive and treatment tools such as expanded education and communication efforts about influenza antiviral drugs, like Tamiflu, which are a second line of defense to treat the virus. Still, the CDC is standing by the more than 170 million doses of flu vaccine expected to be available this fall and winter.
To take out some of the guesswork this season, pharmaceutical giant GlaxoSmithKline's entire vaccine supply will protect against four strains of the virus. Glaxo grows the strains in millions of fertilized chicken eggs.
The egg production process is the most common, generating 90% of the U.S. flu vaccine supply.
But earlier this year, another unexpected hurdle in that production process emerged. Bird flu killed an estimated 50 million birds in 15 states and put vaccine manufacturers on high alert, even though they don't necessarily need eggs that are safe for consumption.
Still, that dependence on nature has led some drugmakers to look at alternatives, such as recombinant technology, which the FDA approved in 2013.
That method uses animal cells to grow flu viruses, and it could cut down the manufacturing time from 24 weeks to 16 weeks. It uses a flu virus protein, combined with portions of another virus grown in insect cells. That process requires no eggs and takes six to 12 weeks.
Protein Sciences was granted FDA approval in 2013 for its FluBlok vaccine. FluBlok, which doesn't require eggs for production, takes less time to manufacture than more conventional means, but the vaccine has a shelf life of around six months.
The shorter production time is important, because the more time the manufacturer has to make a vaccine, the greater the number of doses will be able to be produced.
In the future, flu vaccine producers may be able to deliver a universal vaccine, administered once, that would target parts of the flu virus that don't mutate. But in an industry that sells individual pills for $1,000, a $2 shot is not exactly an incentive for innovation. In fact, some drugmakers are even getting out of the flu vaccine business. Novartis in August sold its flu vaccine arm to Australian biotherapy company CSL for $275 million.