evidence: Concerns over the potential health effects of residual DNA in biological products like vaccines aren’t new or unknown to regulatory agencies. In fact, recommended guidelines for acceptable levels of residual DNA were already established by the World Health Organization and the U.S. Food and Drug Administration prior to the COVID-19 pandemic. Vaccines containing DNA, such as the chickenpox vaccine—a live attenuated vaccine containing a DNA virus—have also been widely used before the pandemic and have been shown to be safe.