Long manufacturing timeline hampers annual flu vaccine strain selection, experts say

By Zachary Brennan

- Last updated on GMT

Long manufacturing timeline hampers annual flu vaccine strain selection, experts say

Related tags Flu vaccine Influenza

US government scientists told a House subcommittee on oversight and investigations on Tuesday that the six months production time necessary for flu vaccine manufacturers can create difficulties for health experts selecting the appropriate virus strains early in the year.

The strain currently in the widest circulation this season –  a subtype of influenza A called H3N2 – differs from the strain included in this year’s vaccine, according to the CDC (Centers for Disease Control), which is why the effectiveness rate is at about 23%. That rate compares with an effectiveness rate of 51% for the 2013-2014 season.


Despite recent advances in flu vaccine manufacturing that eliminates the need for eggs in the manufacturing process, companies are still tasked with selecting the appropriate strain and producing millions of doses before flu season begins in the fall.

In her testimony, Karen Midthun, FDA’s Director of its Center for Biologics Evaluation and Research, said, “Manufacturing of each antigen to be included in the vaccine occurs sequentially over several months, usually from December (produced at risk by the manufacturer before the strain recommendations are made) until late May​.”

FDA also develops and calibrates reagents to help manufacturers test for vaccine potency, and then collects the testing results along with samples from lots before a company can make any commercially available. Doses are then released between August and early October.

New Approaches

Midthun noted that there’s currently a collaboration between BARDA (Biomedical Advance Research and Development Authority), CDC, NIH and FDA that is looking to speed up a number of aspects of the manufacturing process, including potency testing, which requires “new approaches using more modern platforms.  There are some tests being planned and embarked on later this year to make standard potency assays and manufacturers are testing their feasibility​.”

The initiative between the agencies “cut weeks off the vaccine manufacturing process and increased production yields​,” Dr. Robin Robinson, Director of BARDA, said.

Midthun also said another goal is to try to identify high-growth viruses that lead to good yields. And as far as sterility testing: FDA shifted in 2012 to allow more flexibility, with manufacturers now using novel testing methods, which can be “completed in five or six days​,” Midthun said.

Robinson also noted some deficiencies in US capacity, with Protein Science’s Flublok​ as the only recombinant vaccine to not rely on eggs as a means of production. And since it’s a relatively new vaccine, “they’re just scaling up to the market​,” he said. Robinson added that BARDA supports projects to build larger facilities to produce tens of millions of vaccine doses. 

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