Remember, infections uncommon in your area are never farther away than an airplane ride. The first reliable vaccine was developed by Edward Jenner in 1796, to prevent smallpox. Louis Pasteur developed an anthrax vaccine for animals in 1880 and a rabies vaccine for humans in 1885. The pace of vaccine research accelerated in the 1950s and 1960s with advances in laboratory methods for growing microbes in cell cultures. The pace is accelerating again now, with recent advances in biotechnology.
Scientists develop a candidate vaccine based on what they know of microbiology and human immunology.
The candidate vaccine is tested in animals, then tested in people in three stages or phases. I studies involve a dozen people to see if the vaccine provokes an antibody response, and to begin collecting information about vaccine safety. Phase II studies usually include one or two hundred people, to gather more information about effectiveness and to determine the proper dosage. A safe drug is considered to pose a reasonably low risk of harm, injury, or loss when used in an appropriate manner. Because vaccines are typically given to healthy people, without disease, vaccines are held to the highest standards of safety of all medications.