Company receives go-ahead from the Centers for Disease Control.

One month after Sanofi, Seqirus and GlaxoSmithKline (GSK) shipped their first doses of flu vaccines to the US, AstraZeneca (AZ) has shipped its first batches of the nasal spray flu vaccine FluMist Quadrivalent.

The company missed the two previous flu seasons because the Centers for Disease Control’s (CDC’s) Advisory Committee on Immunization Practices (ACIP) advised against its use due to poor real-world effectiveness between 2013 and 2016. AZ has suggested that the reduced effectiveness of the nasal spray may have due to the use of an inappropriate H1N1 vaccine component (A/Bolivia H1N1 strain), which it has replaced with a different A/Slovenia type. 

Development of the vaccine, which is based on live attenuated virus (unlike most flu vaccines), is a complex process that takes more than 12 months. AZ, therefore began working on the FluMist vaccine for the 2018-2019 well before it received a positive recommendation from the ACIP, which came in February 2018. The recommendation was based on results showing that A/Slovenia induced significantly higher antibody responses in the U.S. in children aged 2 to 4, with seroconversion rates comparable to those observed during previous seasons, in which FluMist seemed to be effective.

Since then, AstraZeneca has been working “diligently to ensure we make as much supply available as possible,” according to the company.