COVID-19 vaccines are not “being used to cure cancer,” as social media posts falsely claim, misinterpreting President Joe Biden’s reference to mRNA cancer vaccines during his State of the Union address. Biden was referring to the mRNA technology used to make the COVID-19 vaccines and being studied by researchers to treat cancer.

The Pfizer/BioNTech and Moderna mRNA COVID-19 vaccines are the first vaccines using the messenger RNA technology to be approved for use, but they’re not the first ever developed. The history of mRNA vaccines started decades before the pandemic, and included research on mRNA cancer vaccines.

Unlike platforms used in other vaccines, the mRNA technology doesn’t directly introduce an antigen, such as a protein, into the body to trigger an immune response. Instead, mRNA encapsuled in a fatty envelope delivers instructions for cells to make proteins. The immune system responds by producing antibodies and immune cells, preparing the body to respond if it encounters these proteins again.

The research on cancer mRNA vaccines both enabled the development of mRNA COVID-19 vaccines and was accelerated by it. Now, several clinical trials are testing mRNA vaccines to fight different kinds of cancers — and some have shown promising early results.