President Donald Trump spoke several times about a promising vaccine against COVID-19 that will soon enter human trials. The vaccine was developed and produced in just 42 days. It’s a different kind of vaccine and is unlike any that are currently licensed for humans. While most vaccines are made from pieces of germs or comprised of a live but weakened version of the germ, this new type of vaccine is made from messenger RNA (mRNA).

Recalling DNA and how it works is important for understanding mRNA vaccines. DNA is the stuff that makes up our genes. It contains the instructions for making all of the proteins in our body. In turn, proteins are the building blocks of our skin, heart, and other organs. Additionally, proteins play a major role controlling the chemical processes in our body.

DNA is viewed as the master blueprint for the body and is kept safely within the nucleus of each cell. A copy of the DNA coding for a protein is made out of mRNA. The mRNA leaves the nucleus and makes its way to the protein producing machinery in the cell. The machinery reads the mRNA and produces the specified protein.

Interestingly, viruses hack the protein-producing machinery. When a virus enters a cell, mRNA copies of the viral genes are produced. The viral mRNA is read by the cell machinery and viral proteins are produced. The cell is converted into a virus-producing factory. These newly produced viruses leave the cell to infect other cells in the body and may even spread to other people.

Our bodies fight back. The immune system recognizes the viral proteins as foreign and releases all sorts of chemicals to slow the virus. Some of the chemicals call in immune cells that kill the infected cells or gobble up free viruses. If all goes well, the immune system eliminates the virus. The immune cells produce antibodies that protect against future infections.

So, how do mRNA vaccines work? The vaccines contain mRNA that codes for viral proteins. Once injected, the mRNA is picked up by the cells and the viral proteins are made within the cells. Because the mRNA only contains the information for a few viral genes, new virus cannot be produced. As with a viral infection, the immune system recognizes the viral proteins and kicks into action.

Similar to an infection with a virus, antibodies are produced against the viral protein. Unlike an actual infection, the production of viral proteins is very limited as the mRNA breaks down rapidly. Unlike live vaccines, mRNA doesn’t replicate and so these vaccines are safe in even immunosuppressed individuals.

In the case of COVID-19, the mRNA is for the virus spike protein. The name coronavirus comes from the spike protein on the virus surface making it appear somewhat like a crown. Research on other coronaviruses such as MERS and SARS indicate antibodies against the spike should be protective. Hopefully, the human trials demonstrate the vaccine to be safe and effective.

Vaccine Smarts is written by Sealy Institute for Vaccine Sciences faculty members Drs. Megan Berman, an associate professor of internal medicine, and Richard Rupp, a professor of pediatrics at the University of Texas Medical Branch. For questions about vaccines, email

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