Yes. Vaccines are safe. Millions of children and adults are vaccinated every year. However, any medicine can cause reactions in some people. The most common side effects are swelling or tenderness at the injection site and fever. Serious reactions are very rare, happening in 1- 2 people out of a million shots given. Thousands of people take part in clinical trials to test a vaccine before it is licensed by the Food and Drug Administration (FDA). After it’s licensed, the Vaccine Adverse Events Reporting System (VAERS) helps track any health effect that happens hours, days, weeks, or even months later. Anyone can report a possible side-effect so that it can be studied. This monitoring helps ensure vaccines are safe. To learn more about vaccine safety from the Centers for Disease Control and Prevention, visit the CDC vaccine safety page.