Vaccines are extremely safe and harm is rare. Worldwide, more than 30 000 vaccine doses are delivered per second through routine immunization programs, which, in turn, prevent an estimated 2 million to 3 million deaths annually. The occurrence of serious adverse events, such as those that result in death, threaten life, require inpatient hospitalization, or result in significant disability, are rare (eg, <1 adverse event occurs per 10 million doses for tetanus toxoid vaccines, 1-2 adverse events per 1 million doses for inactivated influenza vaccine, and none for hepatitis A).