What is an mRNA vaccine?


Hi, my name is Kate Mullane. I'm an infectious disease physician at the University of Chicago, and I've been working on the vaccines against COVID. The first two vaccines approved for early use by the FDA to fight SARS-CoV-2, the virus that causes COVID-19, are both mRNA vaccines. While they are the first messenger RNA vaccines to be approved for widespread use in the US, mRNA vaccines aren't actually that new.

The vaccine platform was initially developed in the early 1990s, in an effort to create safe and effective vaccines in a pandemic situation. mRNA vaccines have been developed for other diseases like rabies, Ebola, and Zika, and a large-scale influenza trial was carried out in humans from 1993 to 1996. Over the past 10 years, researchers have been improving messenger RNA vaccine effectiveness. Thanks to billions of dollars in global funding and thousands of scientists and physicians working for months, we've been able to fit years of research and analysis into just 10 months, without skipping any regulatory or testing steps to development of the COVID-19 vaccine.

How vaccines work

Most vaccines work by presenting your body with a weakened or dead version of a virus or some of the proteins found on the surface of the virus. By showing the virus or parts of the virus to your immune system, the vaccine teaches your body to recognize the pathogen and turns on production of antibodies, which are proteins that attach to the virus and allow killer immune cells to gobble it up. Or in the case of COVID, the antibodies glom onto the spike protein. The spike protein is what the SARS-CoV-2 virus uses to attach to cells and infect them. An antibody against this protein prevents the virus from attaching to human cells, so the virus can't infect those cells.

How does an mRNA a vaccine work and how do we know that they're safe?

The mRNA vaccine platform mRNA or messenger RNA, vaccines teach the immune system to make memory cells. So that if you are exposed to the virus at a future date, the immune system has the ability to rev up production of antibodies rapidly and fight off the pathogen again. An mRNA vaccine is a copy of the genetic code used by the SARS-CoV-2 virus to make the spike protein. When the COVID-19 epidemic arrived, researchers from around the world sprang into action to identify and insert the correct genetic code into the mRNA platform.

mRNA vaccines give that recipe to our immune system. Rather than presenting your body with the dead virus or parts of the virus, mRNA vaccines show your body the blueprint needed to make a viral protein. Your body uses that blueprint to make the SARS-CoV-2 spike proteins without including any part of the virus itself. Once the body has created those spike proteins, the proteins are seen by our immune system and the immune system is able to respond in the same way it would to being infected with a live virus.

How do we know the mRNA vaccine is safe?

In this way, it works just like any other vaccine platform. Preparing your body to fight against the virus if it's ever encountered in the future. However, unlike attenuated or killed vaccines, the person is not infected with a virus, not even one that's been weakened or killed. mRNA is a small fragile fragment of genetic information that's rapidly broken down within the bloodstream and within cells.

Well, it's a type of genetic material. It cannot interact with, bind to, or affect DNA. It cannot even enter the cell's nucleus where the DNA resides. mRNA is broken down rapidly by enzymes in the bloodstream and in the body once its code is translated to make protein. With advances in technology, it's much easier and less expensive to make messenger RNA and mRNA vaccines in the laboratory, making it easier to produce lots of vaccines, fulfilling the hope for rapid production of safe and effective vaccines during a global pandemic.

So far, the COVID-19 vaccines appear to be extremely effective, up to 95% effective, and very safe, with allergic reactions reported in only 6.1 cases per one million doses administered. While producing and distributing enough vaccine for a global population is an enormous challenge, it's one we're grateful to have. As a physician, it's my hope that these new vaccines will allow us to protect our communities and ourselves and finally overcome COVID-19.

Watch part one: How do vaccines work?

Watch part two: What are the different types of vaccines?

Watch part three: How are vaccines made

Watch part four: How does the FDA approve vaccines?