A widely used flu vaccine isn't working

A flu vaccine that's sprayed up the nose has only been effective in about 3% of those who use it, according to new data from the CDC.

That 3% "means no protective benefit could be measured," and the vaccine won't be used for the 2016-2017 flu season, the CDC said in a statement Thursday.

In response, AstraZeneca, the company that makes the vaccine, said it would take an $80 million writedown on stocks of the vaccine, called FluMist Quadrivalent.

The U.S. Centers for Disease Control and Prevention (CDC) ruled the vaccine should not be used in any setting, based on U.S. data indicating it did not demonstrate statistically significant effectiveness in children.

Despite the setback, AstraZeneca said it maintained its financial guidance for 2016. U.S. sales of the product in 2015 totaled $206 million.

The company said the CDC data contrasted with its own studies as well as preliminary independent findings by public health authorities in other countries suggesting the vaccine was 46 to 58 percent effective overall against flu strains during the 2015-2016 season.

"The distribution and use of the vaccine in other countries are progressing as planned for the forthcoming influenza season, pending the annual release process from relevant regulatory authorities," AstraZeneca said in a statement on Thursday.

FluMist is currently the only non-injected form of flu vaccine, and in the past, the CDC had recommended the nasal spray over injection for young children. The CDC is still recommending annual flu vaccination.

(Reuters reporting by Ben Hirschler)