Flu vaccines, previously problematic for the egg-allergic, are now deemed safe

New guidelines say doctors don't have to ask about egg allergies before administering flu shots.

As the U.S. enters a potentially rough influenza season, health experts are presenting new vaccination guidelines saying there's no safety difference for flu shots given to people with egg allergies and those without.

Historically, healthcare practitioners asked up front whether flu vaccine recipients are allergic to eggs and sometimes monitored them after administering the shot. New guidelines published in the Annals of Allergy, Asthma & Immunology say there's no need for doctors to even ask whether recipients are allergic. 

Previous concerns that trace amounts of egg protein in the vaccines could trigger an allergic response were unwarranted, according to the experts. About 2% of children in the U.S. are allergic to eggs. 

Though new vaccine technology is entering the market, top flu vaccine makers still produce tens of millions of doses every year in a process that uses chicken eggs. 

But while the guidelines will likely assuage concerns about allergic reactions, the egg-based production method has come under fire lately for efficacy. A group of experts recently predicted the flu vaccine could be just 10% effective this year, pointing to the decades-old manufacturing process as a potential culprit.

The efficacy problem isn't because of strain drift, or a difference in the strains covered by flu shots and those circulating in nature, the team wrote in a New England Journal of Medicine commentary. Rather, it's because the circulating strains are "antigenically less similar to egg-grown A(H3N2) viruses used for producing the majority of influenza vaccines in the United States," they wrote.

Still, the officials stressed, any protection is better than none. A separate team with the University of Pennsylvania had documented the same dynamic in an earlier study. 

Meanwhile, top flu shot players Sanofi and Seqirus offer vaccinations that use alternative manufacturing technologies, and Seqirus this year became the first vaccine maker to produce cell-based flu immunizations on a commercial scale. 

Sanofi picked up its recombinant protein-based flu vaccine, Flublok, through its Protein Sciences buyout earlier this year. Seqirus, for its part, was established when Novartis sold its flu vaccine outfit to Australia's CSL; the CSL unit is producing vaccines at a massive former Novartis plant in North Carolina. 

Questioned about the 10% efficacy prediction for flu vaccines for the upcoming season, a Sanofi Pasteur executive wrote to FiercePharma that with 150 million doses of flu shots needed each year in the U.S. alone, “egg-based vaccine production remains the most reliable, time-proven method," adding that it "represents the vast majority of vaccines used globally to help prevent influenza.”