Some vaccine production methods for COVID-19 have been using mRNA to trigger the body’s immune system to produce protective antibodies without using the actual virus. While vaccines for some other illnesses — such as the varicella (chickenpox) vaccine — actually use bits of the virus in the vaccine to create what’s called a “live virus vaccine,” the Pfizer and Moderna COVID-19 vaccines being produced do not contain a live virus. Instead, some coronavirus vaccine candidates essentially work by using synthetic mRNA to direct the body to produce a small amount of the spike protein. Once the vaccinated person’s immune system detects this protein, their body begins producing protective antibodies to defend against coronavirus. Experts say that the protective antibodies will recognize and prevent COVID-19 from getting into the body’s cells in the future, should that person be exposed to coronavirus.