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MARK SAWYER, MD: I don't know what it means to "green" a vaccine. You hear that expression out there and I think the intent is to suggest that there are things in vaccines that we don't need. But actually, every ingredient that's in a vaccine is in there for a reason and they've all been tested, they're all safe, and if we didn't have the ingredients in there, the vaccines wouldn't work.

PAUL A. OFFIT, MD: I think what it refers to is the false notion that vaccines contain harmful preservatives or chemicals or additives or something that's doing harm and that we want to get away from all that.

But the fact of the matter is that vaccines contain elements that we typically encounter and manage every day and they are green, because they are made from nature.

The fact of the matter is that when you take a viral vaccine or a bacterial vaccine they are made from the natural product that is weakened or inactivated in such a way that it can't cause harm, but that it can induce an immune response that's protective. It's all natural. That's why it works.

MARY BETH KOSLAP-PETRACO, DNP(c), CPNP: When vaccines are manufactured, they're manufactured under the strictest of standards so that we make sure that there's not contamination, that there's nothing going into the vaccines that are not expected to be in there. We clearly know what's in our vaccines. I think our vaccines are green right now.