What are mRNA vaccines?

Ask the doctor

Q. What are mRNA vaccines, and could they prevent other diseases besides infections?

A. The very first vaccines approved in the United States to prevent COVID-19 are a new type: mRNA vaccines. The way any type of vaccine works is to train a person's immune system to recognize and attack a target, like a virus, when it enters the body. A vaccine does that by "showing" the immune system either a harmless (dead or weakened) virus or a critical piece of the virus' protein coat. With the COVID-19 virus, that critical piece is called the spike protein.

With traditional vaccines, the harmless virus or critical piece of protein is introduced into the body, usually with an injection. But producing large amounts of dead or weakened viruses, or of the critical piece of protein, takes a lot of time and trouble. About 30 years ago, several scientists imagined an easier, much faster way: mRNA vaccines.

The idea of an mRNA vaccine is simple enough. The mRNAs of a virus directs the production of its protein coat. Scientists can pretty easily manufacture an mRNA that makes the spike protein. What if you injected the mRNA for the spike protein into someone, and the mRNA then traveled through the bloodstream, was gobbled up by immune system cells, and then those cells started to make the spike protein? Would that educate the immune system to attack the virus?

A simple idea, but the scientists encountered one barrier after another. As soon as one was overcome, another appeared. Decades elapsed, without any guarantees the approach would work, with many experts saying it never would, and with the money to do the work getting harder to come by.

When COVID-19 came along, and the world was desperate for rapid answers, the scientists rapidly created an mRNA vaccine — and it worked! I tell the story in more detail in a Harvard Health blog post (/mrna).

You ask if mRNA vaccines could prevent or treat other diseases besides infections. Cancerous cells create unique pieces of protein that are not found on healthy cells, pieces that can be targeted by a vaccine. Recently, scientists have reported encouraging initial success in treating melanoma with such a vaccine.

Two key scientists in this story are Turkish immigrants to Germany who met, fell in love with the idea of creating an mRNA vaccine, and then fell in love with each other. According to The Wall Street Journal, one day in 2002 they took a break for lunch, got married, and then returned in the afternoon to their laboratory to finish an experiment. Scientific breakthroughs require brains, the courage of one's convictions, and passionate obsession. Plus the willingness of the rest of us to invest in smart, passionate people who just might change the world.

— Anthony L. Komaroff, M.D.
Editor in Chief, Harvard Health Letter

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