Safe vaccines are critical to fighting diseases, from polio to COVID-19. Evidence shows that the protection provided by vaccines currently licensed in the U.S. outweighs their potential risks. In general, side effects from vaccines are less acceptable to the public than side effects from treatments given to people who already have a disease. Also, misinformation and safety concerns may cause people to delay or refuse a vaccine—possibly increasing deaths. We looked at vaccine safety and its challenges, including: ensuring public confidence addressing misinformation identifying rare and long-term effects