US immunisation advisors of the Centers for Disease Control and Prevention is advising against use of AstraZeneca's FluMist Quadrivalent for the 2016/17 influenza season.
Updated guidelines state that the vaccine should not be used in any setting, after CDC vaccine effectiveness data from the last three influenza seasons in the US indicated that FluMist was not significantly effective in children two-17 years of age.
However, AZ said the data contrast with its own studies "as well as preliminary independent findings by public health authorities in other countries" that show its vaccine was 46-58 percent effective overall against the circulating influenza strains during the 2015-2016 season.
It is generally accepted that when there is a good match between the strains of the virus in the vaccine and those circulating during a particular season, vaccines are typically 50-60 percent effective.
The drugmaker said it is now working with the CDC to better understand its data to help ensure eligible patients continue to receive the vaccine in future seasons in the US.
FluMist pulled in US product sales of around $206 million, but the new guidelines meant that demand in the country during the second half of the year is expected to be very limited. As a result, the firm will take an inventory write-down of around $80 million in the second quarter.