With CDC backing reinstated, AstraZeneca ships FluMist for the coming flu season

Having missed two flu seasons, AstraZeneca is looking to a comeback in the U.S. with its nasal spray flu vaccine FluMist Quadrivalent on the back of CDC vaccine advisory group endorsement. But supply is limited.

The British Pharma announced on Tuesday that it has shipped FluMist for the 2018-19 season, more than a month after Sanofi, Seqirus and GlaxoSmithKline sent their first batches. It has manufactured 2.7 million doses for the U.S. in this season, Lily Cappelletti, a company media aide, told FierceVaccines. That's far fewer than its peers.

Unlike most flu shots, which are inactivated vaccines, FluMist is live attenuated. Because it requires a complex manufacturing process, development begins over a year ahead of the next flu season. AZ started making this season’s supply based on the initial demand estimates and prebook orders from healthcare providers before the CDC’s Advisory Committee on Immunization Practices gave the thumbs-up in February, explained Cappelletti.

“Since the renewed ACIP recommendation, we have been working diligently to ensure we make as much supply available as possible for the 2018-19 flu season despite the complex and unique manufacturing process,” she said.

FluMist was dealt with major blows in the previous two seasons as the ACIP advised against its use due to poor real-world effectiveness between 2013 and 2016. In the 2015-16 season, for example, the CDC found that the nasal spray showed practically no protective benefit in children aged 2 to 17, compared with 63% for flu shots, even though data from authorities in the U.K. and Finland showed that FluMist was around 46% to 58% effective.

RELATED: AstraZeneca's FluMist wins CDC committee's backing after two missed years

AZ has said the reduced effectiveness might be linked to the unfit H1N1 vaccine component. Since the vaccine was rejected by the CDC, the company has changed the old A/Bolivia H1N1 strain into a different A/Slovenia type.

Data compiled by AZ in the U.S. in children aged 2 to 4 showed that A/Slovenia induced significantly higher antibody responses than its predecessor, and seroconversion rates were comparable to what was observed during seasons in which it seemed to be effective. Based on that, the committee voted 12-2 in favor of the vaccine in the coming season.

RELATED: GlaxoSmithKline, Seqirus launch first round of flu shots for upcoming season

Following the renewed ACIP backing, Public Health England also published provisional results, which demonstrated that FluMist, known as Fluenz Tetra in the EU, provided statistically significant effectiveness against H1N1 strains during the 2017-18 season in children 2 to 17 years of age.

Despite those new data, the American Academy of Pediatrics recommended that flu shots should be used over the nasal spray, reasoning that the effectiveness of the latest FluMist version remains unknown.

FluMist’s future in the U.S. might hinge on its performance this season, but Cappelletti said it might be difficult for the CDC to collect real-world effectiveness data in the U.S. because of the low amount of uptake. But she said “AstraZeneca is evaluating internally and with the FDA to determine how to monitor effectiveness for future seasons.”  

FluMist offers another option for those who dislike needles, but flu shots from Sanofi Pasteur, Seqirus and GSK are more widely used and will be supplied at 70 million, 50 million and around 40 million doses, respectively, for the upcoming season.