Kathryn A. Whitehead

This one is a polymer called polyethylene glycol.

So let's call it PEG.

That's much easier.

So PEG is a water-loving molecule.

So it surrounds the lipid nanoparticle, and it holds it all together.

You can think of the other three lipids as the box and the bubble wrap for the mRNA, and the PEG as the packing tape.

You may have heard in the news about a tiny fraction of people that have allergic responses to the vaccine.

There is some evidence that PEG could be contributing to these allergic reactions.

And that's because people are routinely exposed to PEG in cosmetic and household products, and some people have already developed antibodies against PEG.

But why would this happen to some people and not to others?

It turns out that every person's immune system is different, and just the same way that some people are allergic to latex, other people are allergic to PEG.

It's important to keep in mind, however, that PEG has had a long history of safe use as part of FDA-approved drug formulations, and these vaccine allergies could be caused by things other than PEG.

More research is needed to get to the bottom of these side effects.

All right, so let's take a step back and look at our whole nanoparticle.

When these ingredients all fit together nicely, the result is a delivery woman's dream.

In the case of the vaccines, after these nanoparticles get injected into our muscle, they take the mRNA into our cells

There, the mRNA acts like an instruction manual that tells our cells to make a foreign protein, in this case, the coronavirus spike protein.

When our immune cells see the spike protein, they rush to protect us from it, and they teach themselves to remember it so that they can kill it if it ever returns.

As we speak, the mRNA vaccines are out there, saving lives from the coronavirus.

They were our first and best tool to combat this nightmare, and they are our best hope of responding swiftly to viral variants because we can keep our lipid nanoparticle packaging the same, and all we have to do is swap out the mRNA that's inside.