mRNA vaccines are a type of vaccine that use messenger RNA to instruct cells in the body to produce a harmless piece of the virus that causes a specific disease. This piece, known as a protein, triggers an immune response, helping the body recognize and fight the actual virus if exposed in the future. Unlike traditional vaccines, which often use weakened or inactivated forms of a virus, mRNA vaccines do not contain live virus particles. They are designed to be safe and effective, and have been used successfully in combating diseases like COVID-19.