Vaccine producers have made flu shots with eggs for decades, but a new study says the manufacturing process curbed the efficacy of last year's shot and warns that the problem could repeat this year.
Egg-based vaccines didn't properly protect against an H3N2 virus mutation during last year's flu season, according to a research team from the University of Pennsylvania. That's because current H3N2 viruses "don't grow well in chicken eggs, and it is impossible to grow these viruses in eggs without adaptive mutations,” Scott Hensley, Ph.D., an associate professor of microbiology at Penn, said in a statement.
This year's flu vaccines contain the same H3N2 influenza strain as last year, the study authors said, so efficacy may suffer if that strain ends up in circulation. According to the CDC, flu vaccines were 42% effective last year.
And that means it's time to develop new vaccine manufacturing methods, the study authors said, while noting that it's still worthwhile for everyone to be vaccinated. “Our data suggest that we should invest in new technologies that allow us to ramp up production of influenza vaccines that are not reliant on eggs,” Hensley continued.
But he stressed that people should still get the recommended flu vaccine because "some protection against H3N2 viruses is better than nothing, and other components … will likely provide excellent protection this year.” The work was published in the Proceedings of the National Academy of Sciences.
A vast majority of flu vaccines are still made with eggs by the market's top players—Sanofi, Seqirus and GlaxoSmithKline—but industry has been working to advance cell-based options.
Even influenza vaccine manufacturers are recognizing that, over time, the egg-based production process will become obsolete and will be replaced with a more modern production process," she said.
Seqirus, the second-largest flu vaccine company, over the summer touted its industry-leading capacity for large-scale production of cell-based shots. A unit of Australia's CSL, the company is using a massive former Novartis plant in North Carolina for its cell-based flu vaccine production.
GlaxoSmithKline, for its part, has a partnership with Valneva researching flu shots based on the biotech's EB66 cell line.
Flu vaccine efficacy has fluctuated over the years, ranging between 10% in 2004-2005 and 60% in 2010-2011, according to the CDC.