US CDC Advisory Committee retracts endorsement of AstraZeneca's FluMist

Updated guidance by the Advisory Committee on Immunization Practices (ACIP) of the US Centers for Disease Control and Prevention (CDC) states that AstraZeneca’s (LSE: AZN) FluMist Quadrivalent nasal vaccine should not be used in any setting, based on CDC vaccine effectiveness data from the last three influenza seasons in the USA, which indicated FluMist Quadrivalent did not demonstrate statistically-significant effectiveness in children 2-17 years of age. FluMist was once regarded as the best vaccine for protecting children against flu.

The US 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. These findings demonstrate FluMistQuadrivalent was 46%-58% effective overall against the circulating influenza strains during the 2015-2016 season. As influenza vaccine effectiveness varies from season to season, it is evaluated in annual observational studies. The CDC states that when there is a good match between the strains in the vaccine and those that circulate during the influenza season, vaccines are typically 50%-60% effective. AstraZeneca is working with the CDC to better understand its data to help ensure eligible patients continue to receive the vaccine in future seasons in the USA.

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.