Covid Clarity: A Vaccine Like No Other

The rollout of Pfizer’s COVID-19 vaccine was greeted with celebration, relief, and — for some — worry and doubt. There are a lot of questions and some skepticism about a vaccine that was developed with record-breaking speed. Is it safe? Is it necessary? Who should rush to get it, and who should wait? Dr. Michael Lederman, an immunologist, professor, and researcher at Case Western Reserve University School of Medicine, answers our questions

We know that this vaccine is different from a typical vaccine, since it’s a messenger RNA (mRNA) vaccine. What are the ramifications of that difference?

In earlier vaccines, the antigen is introduced to us either as a protein (sometimes a sugar) or as part of a virus. In this instance, the antigen is introduced through messenger RNA (also known as mRNA).

We use mRNA in our own cells to make proteins. The strategy behind this new vaccine takes the RNA sequences that encode an important protein of the virus, encapsulates it in a little fat globule, and then injects it into the muscle. Our cells then take up that sequence and translate that RNA code into a protein, and the protein that our cells make is the actual immunogen — it drives an antibody response that we use to protect ourselves.

So while earlier vaccines provided a target that is recognized by our body’s antibodies and white blood cell “soldiers” to fight infection, here we’re putting RNA into our own cells and asking those cells to make that immunogen target that is recognized by our immune antibodies and white blood cell soldiers. It’s as if we’re enlisting the body in the fight just one stage earlier than with a typical vaccine.

That’s exactly right. Ordinarily we introduce the protein immunogen inside the vaccine. In this instance we’re introducing a message that our cells make into the protein, which then induces the immune response.