According to the CDC, vaccine effectiveness during the 2015-2016 flu season was 47%, but for the 2014-2015 season, effectiveness was just 19%. Variances in effectiveness from year to year can be caused by a variety of factors.
As detailed in prior blog entries, each year before the flu season begins, a vaccine is made based upon predictions on which strains are likely to be most prevalent that year. The selected strains are then distributed to vaccine manufacturers, which produce them and distribute them to health care professionals. As such, to the extent that such predictions are incorrect, they can result in limited effectiveness since vaccine effectiveness varies depending on how well it matches the circulating virus strains.
Other problems in vaccine effectiveness can result from issues with the manufacturing process itself which often involve propagation in chicken eggs. For example, limited effectiveness in the past has been thought to occur in some instances due to a mutation that occurred in the H3N2 vaccine strain. This vaccine mutation was thought to result from an egg based manufacturing process commonly used today. Researchers found that as soon as the virus was grown in the eggs, it started to acquire a mutation that made it less effective when incorporated into the vaccine. Unfortunately, that is the strain that many predict will be the dominant strain for this year’s flu season.
Lastly, there can be limited effectiveness based upon evolution and changes in the viruses themselves. As viruses change, the vaccines that were produced in response to earlier forms of the virus become less effective in dealing with them. Because of all of this, the flu virus is notoriously unpredictable and in some instances, flu shots can result in significant injury.
If you or a loved one sustained an injury or started experiencing symptoms after receiving the flu shot, please contact our Vaccine Injury Attorneys as you may be entitled to compensation under the National Vaccine Injury Compensation Program (NVICP). Our firm is experienced in litigating vaccine injury claims on behalf of those suffering these types of injuries.