Can virus vaccines cause autoimmune reactions?

DEAR DR. ROACH » I have been reading about the new COVID-19 vaccines. Since at least some of these vaccines work by getting a person’s own body to generate the antigen, what is to stop it from inducing an autoimmune response?

— F.M.

DEAR READER » An autoimmune reaction is when the body reacts to its own cells. There are many autoimmune diseases: Type 1 diabetes, for example, is an autoimmune response to the cells that make insulin. Hashimoto’s thyroiditis causes the body to attack thyroidproducing cells. In other autoimmune diseases, such as rheumatoid arthritis or systemic lupus erythematosus, the body response is much more complex. What triggers the body to start attacking its own cells and tissues is poorly understood in most cases.

At least two of the new COVID-19 vaccines use mRNA (for “messenger” RNA). This type of RNA takes genetic information from the DNA and brings it to the protein-making part of the cell. Think of DNA as a blueprint for making RNA, which is what is used to make proteins. This strand of RNA genetic material enters the body’s cell and causes the person’s own cells to make a particular viral protein, called the spike protein. Some spike protein is sent outside the cell, where it stimulates production of antibodies to the spike protein, which will help the body fight off COVID-19 if it gets exposed. In addition, the spike protein is also expressed on the cell surface in connection with proteins called MHC-1 complex. This combination stimulates the Tcells of the body to also be ready to fight off COVID19-infected cells.

The mRNA is never taken up into the cell nucleus, and cannot become part of the person’s own DNA. In fact, the mRNA is destroyed by the cell’s own processes after the cell has made the spike protein. As such, the vaccine should not be able to trigger an autoimmune response, since it is causing a reaction to the spike protein, which no cells of the body normally express.

You can read more about mRNA vaccines at www.cdc.gov/ coronavirus/2019-ncov/ vaccines/different-vaccines/mrna.html