Cell-based flu vaccine 20% more effective than egg-based vaccine this flu season, says FDA chief

Brian Zimmerman -

Flucelvax, the only influenza vaccine developed in the U.S. with cell cultures, may have been 20 percent more effective than standard vaccines developed in eggs this flu season, according to comments made by FDA Commissioner Scott Gottlieb, MD, cited by STAT

Here are five things to know.

1. Gottlieb first mentioned the 20 percent figure during a March 8 congressional subcommittee hearing on oversights and investigations regarding the severity of this year's flu season and the estimated poor performance of the seasonal flu vaccine. The FDA chief confirmed the number in an interview with STAT after the hearing.

"The data aren't final yet, but I'm comfortable saying that I think it's going to be about 20 percent improved efficacy for the cell-based vaccine relative to the egg-based vaccines," Dr. Gottlieb told STAT.

2. The estimate is derived from FDA analysts who have been examining the medical records of 16 million Medicare beneficiaries to determine whether hospitalization rates vary based upon vaccine type and dose.

3. Though the FDA analysis can't break down the data by flu virus type, the dominance of the H3N2 strain is likely a key reason the cell-culture-based vaccination may have outperformed the egg-based vaccine.

4. When vaccines are grown in hen's eggs, they have to adapt, which can sometimes result in mutations. This seems to be especially true with the H3N2 component. Many experts suspect vaccines grown in cell cultures are less likely to acquire mutations, which may contribute to improved efficacy, according to STAT.

5. Gottlieb told the congressional committee it was too soon to say whether vaccines grown in cell culture are definitely more effective, arguing the vaccine developed in hen's eggs actually display more protection against flu in some years. Dr. Gottlieb said more research is needed to know for certain, but if studies confirm the cell-culture vaccine performs better against H3N2, the FDA could "make a recommendation that the H3N2 component has to be produced in a cell-based process and the others can be produced in eggs."

To read the full report from STAT, click here.

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