ARI SHAPIRO, HOST:
You might recall that last month, Health Secretary Robert F. Kennedy Jr. overhauled a group of vaccine experts and replaced them with his own hand-picked panel. Now a matter that some vaccine experts thought was long settled has reemerged. An ingredient in some flu shots called thimerosal could be on its way out. It has been absent from most, but not all, flu vaccines for more than two decades. NPR pharmaceuticals correspondent Sydney Lupkin is here to explain what the ingredient is and why it's getting so much attention. Hi, Sydney.
SYDNEY LUPKIN, BYLINE: Hi, Ari.
SHAPIRO: I'd never heard of thimerosal before this panel met. What is it?
LUPKIN: So thimerosal is a chemical compound that's about 50% mercury by weight. It has a record of safe and effective use as a preservative in vaccines and medicines since the 1930s. That's according to the Food and Drug Administration. But as you said, it's actually absent from the vast majority of flu shots in the U.S. and has been for 20 years. Today, thimerosal is still used in vials containing multiple doses of the vaccine. Here's Dr. Michelle Fiscus, chief clinical officer of the Association of Immunization Managers.
MICHELLE FISCUS: If you're constantly going in and out of the vial to drop a new dose, you run the risk of getting bacteria or fungus into that vial, and we don't want those vaccines to be contaminated.
LUPKIN: Thimerosal's job is to keep the vial from getting contaminated between patients and potentially making someone sick.
SHAPIRO: So why the push to take it out?
LUPKIN: So the question before the meeting of vaccine advisers to the Centers for Disease Control and Prevention last week was whether to recommend against using thimerosal-containing vaccines. It's been a theory among people who are concerned about vaccines that thimerosal causes autism, but study after study has shown it doesn't. Nevertheless, thimerosal was removed from most childhood vaccines in 2001. Dr. Jesse Goodman, a former chief scientist at FDA, also points out that even though thimerosal has been largely absent from vaccines for years, autism rates have gone up anyway.
JESSE GOODMAN: They turned this meeting into solving a problem that doesn't really exist anymore.
LUPKIN: The panel did recommend that people get flu shots that don't contain thimerosal, and that could lead to a shift to just flu shots without it.
SHAPIRO: Is this going to have any impact on how easy it is for people to get vaccinated?
LUPKIN: For most people, there would be no change. Single - according to the CDC, 94% of flu shots in the most recent flu season were thimerosal-free or thimerosal-reduced. Single-dose syringes, which is how most flu shots are given, don't need to have thimerosal. That said, the change could present challenges for some health centers. The multidose vials are cheaper and take up less space in refrigerators than single-dose syringes do, so they would have to adapt. I also reached out to the two companies that make multidose flu shot vials with thimerosal - Sanofi and Seqirus. Both said only a very small number of their doses contain thimerosal and they'll be able to make enough single-dose vials to handle the upcoming flu season.
SHAPIRO: So is there any impact at all to this change?
LUPKIN: You know, in practice, it would be manageable. But what I'm hearing from people like Goodman and Fiscus is that it's the bigger issue of how vaccine policy is being made. They were concerned that the regular protocols weren't followed when the CDC's advisers voted to recommend this move to the agency. The panel seemed to disregard scientific evidence showing thimerosal doesn't cause harm. Goodman says he's concerned this process will undermine confidence in vaccines in the United States and abroad.
SHAPIRO: That's NPR pharmaceuticals correspondent Sydney Lupkin. Thank you.
LUPKIN: You bet.
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