A presentation by scientists on a work group for the Centers for Disease Control and Prevention’s vaccine advisory panel highlighted various alleged “safety uncertainties” of the mRNA COVID-19 vaccines, including those about cancer and changes to the immune system. Scientists, however, told us that many of the cited studies are either misconstrued or of poor quality. As with all medical products, the mRNA COVID-19 vaccines are not 100% safe. But the vast majority of people experience only temporary and mild side effects, which are expected. Serious side effects can occur but are rare.