Vaccines have been used to safely introduce people's bodies to diseases for centuries, and they save millions of lives each year.
By giving people a weakened or dead version of a disease, a vaccine allows the body to develop antibodies which recognize and fight the disease later on.
Early vaccinations used dry scabs from smallpox to promote smallpox immunity. Doctors and scientists across nations took and improved the method, developing vaccines for health crises from whooping cough to polio to COVID-19. This graphic history features famous cases and current challenges, including the time frame for creating a new vaccine.