ATLANTA, June 23 (UPI) -- A non-injected form of the flu vaccine was not effective at preventing influenza infection during the last three years, leading to the U.S. Centers for Disease Control and Prevention to revoke its recommendation for its use.
A CDC panel on Wednesday voted that FluMist Quadrivalent vaccine should not be used at all this year because of an expectation it will not protect patients who receive it, based on data showing it provided basically no measurable protective effects against influenza.
Nasal flu vaccines represent about one-third of all flue vaccines given to children, with FluMist representing 8 percent of the flu vaccine stock in the United States. While this will likely affect vaccine providers who have already placed orders ahead of the 2016-2017 flu season, the agency said it was working to make sure enough doses are available to meet demand.
The vote by CDC's Advisory Committee on Immunization Practices was seen as a bit of a surprise, because the nasal mist form of the vaccine was found effective in clinical trials by its maker, MedImmune, a subsidiary of AstraZeneca, and is popular with patients who are needle averse.
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"Today's ACIP vote highlights the importance of measuring and evaluating the effectiveness of public health interventions, which can have significant implications for public health policy," CDC officials said in a press release. "The change in the ACIP recommendation is an example of using new available data to ensure public health actions are most beneficial."
Preliminary data that became available to the agency in May on effectiveness of FluMist, which has been recommended for several years as preferable for children, showed it was effective against any form of the flu virus 3 percent of the time during the 2015-2016 flu season. Flu shots, however, had about a 63 percent efficacy rate.
The data, according to the CDC, has been consistent now for the last three flu seasons, but the numbers are starkly different from what AstraZeneca reports about the nasal mist.
"The U.S. CDC effectiveness data for 2015-2016 season contrast with studies by AstraZeneca as well as preliminary independent findings by public health authorities in other countries," the company said in a press release. "These findings demonstrate FluMist Quadrivalent was 46 percent to 58 precent effective overall against the circulating influenza strains during the 2015-2016 season."
The CDC last year lowered its FluMist recommendation from preferred to no preference based on the previous two flu seasons, which saw declining efficacy in the previous two years -- including "no measurable effectiveness" during the 2013-2014 flu season.
Flu vaccines are redesigned each year to protect against two, three or four forms of the virus and change each year based on the strains scientists predict will circulate the most during a given flu season. There is no way to predict whether a vaccine will actually be effective, however, which is why some years' vaccines work better than others.
AstraZeneca said it will work with the CDC to understand the newly analyzed data for future flu seasons, adding that the nasal spray form of the vaccine will still be available in other countries.
