Vaccine makers say they're pleased with the effectiveness of this season's flu vaccine, which comes as a relief after mutations led to a tough flu season last year.
Preliminary data from the Centers for Disease Control and Prevention showed that the vaccine was 59% effective overall, and 51% effective against the H1N1 viruses that were responsible for most cases of influenza this season. Overall efficacy rates for the flu vaccine usually range between 47% and 60%, but last year's was only 23% because of a mutation in the virus' dominant strain.
“This is what we would expect,” said Dr. Leonard Friedland, GlaxoSmithKline's company's director of scientific affairs and public health. “It's consistent with influenza vaccines that are being used routinely in the U.S."
GSK decided this season to offer only quadrivalent vaccines, which include four strains of the virus. Many other manufacturers offer quadrivalent vaccines, but Friedland noted that patients who receive traditional three-strain vaccines would have missed out on 25% of the B types of the virus that are making Americans ill this season. Sanofi delivered over 66 million doses of its Fluzone vaccine to the U.S. this season, representing nearly half of the national supply.
Dr. David Greenberg, regional medical head of North America for Sanofi Pasteur, said in a statement the company felt it was delivering an effective vaccine. He added that even when a vaccine doesn't cover all circulating strains, it still can make the influenza illness milder for patients and reduce the potential for severe complications.
CDC officials said positive flu tests have been elevated since mid-January. For the past 13 years, seasons have averaged about 13 weeks in length, ranging from just one week to 20 weeks. According to the CDC, 146.3 million vaccine doses have been distributed as of Feb. 12 and manufacturers expect to provide between 171 million to 179 million doses total.
An FDA spokeswoman said the agency is not aware of any shortages involving the influenza vaccine supply. There can be spot shortages from time to time, but those are generally short-lived, she said.
Most vaccines are ordered in advance of the flu season, but Friedland said GSK is poised to meet any demands for influenza vaccine.
Both executives agreed that the each flu season is unique and unpredictable and that strain activity fluctuates throughout the year.
“The only thing predictable about influenza is that it's unpredictable,” Friedland said. “Our scientists and our public health officials all across the globe work day-in and day-out to gather the most scientific evidence and data they can to predict the strains that will be producing disease that season so that manufacturers are given a direction on what strains are producing the vaccine.”
