Cell-based flu vaccines only slightly better than traditional shots in seniors: FDA study

Recent studies have blamed the egg-based vaccine production process for less effective flu shots. But flu vaccines made from the newer, cell-based technology didn't perform much better in seniors last year either, a new FDA report finds.

Flu vaccines on average didn’t offer much help protecting those 65 and older in the past flu season, posting only 24% effectiveness in the age group, according to the FDA study quoted by the Associated Press. Seqirus’ cell-based Flucelvax offered the best protection among all, but its 26.5% rate is not the improvement some had anticipated.

The vaccine virus undergoes genetic mutations during the egg-grown manufacturing process, and some studies have found that can compromise the final product’s efficacy.

During a congressional subcommittee hearing in March, FDA chief Scott Gottlieb, M.D., said the agency had data suggesting cell-based vaccines performed 20% better than those made in eggs in the 2017-18 season. A recent Rice University study predicted egg-cultured flu vaccine for the coming season will be only 20% effective against the nasty H3N2 strain, whereas effectiveness of a shot made in insect cells could reach 47%.

For its study in seniors, the FDA polled real-world data from more than 13 million Medicare beneficiaries and calculated the flu-related hospitalization cases for each kind of flu shot.

Currently, Seqirus’ Flucelvax and Sanofi’s recombinant Flublok, grown in insect cells, are the only two FDA-approved egg-free flu vaccines. Most flu shots sold today are still made in chicken eggs. Sanofi Pasteur alone delivered 200 million egg-based flu vaccine doses in 2017. In comparison, the U.S. had about 20 million doses produced in cells in the past season, Gottlieb told lawmakers at the March hearing.

Seniors are particularly susceptible to the flu and are historically a tough group for vaccines. Seqirus and Sanofi each have a vaccine designed specifically for people aged 65 and older under different approaches. Seqirus makes Fluad with MF59 adjuvant to elicit a stronger immune response. Sanofi’s Fluzone High-Dose, as its name suggests, includes more antigen than its regular-dose counterpart.

A 2014 controlled study published in The New England Journal of Medicine found Sanofi’s high-dose version posted 24% better efficacy than the traditional version. But the new FDA real-world analysis only showed a slightly better protection, according to AP. However, it’s worth noting that these are not apples-to-apples comparisons because the NEJM study is based on lab-confirmed influenza, while the FDA study looked at hospitalization numbers.

There’s no denying, though, that flu vaccines in general didn’t work well this year. A CDC interim analysis released in February put the 2017-18 season’s overall flu vaccine effectiveness at 36%, and that number dropped to 25% against the H3N2 virus and just 18% for the 65-or-above age group.

Because they appear to hold more promise, Seqirus has been shifting its focus to the newer products like Flucelvax and Fluad. For the six months till the end of last year, Fluad sales grew 130% year over year to $129 million, while revenues from the cell-based Flucelvax quadrivalent shot, approved by the FDA in May 2016, jumped 504% to $308 million. As for Sanofi, it raised Flublok's price 12.5% last season, citing "substantial benefit" over a standard shot.

As companies work to incorporate new technologies to improve seasonal vaccines, the race has begun to develop universal flu shots that can cover multiple strains for many seasons. Big firms including Sanofi and Johnson & Johnson, and biotechs like Imutex, BiondVax, FluGen and Vaccitech, all have eyes on the "holy grail" of flu research.

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