The term “vaccine” is used here with qualification. In the past, the definition of “vaccine” included “A product that stimulates a person’s immune system to produce immunity to a specific disease, protecting the person from the disease.” In 2021 this was altered, removing “stimulates a person’s immune system to produce immunity” to now state, “A preparation that is used to stimulate the body’s immune response against diseases.” The 2015 WHO document, “Module 2: Vaccines and drugs: similarities and differences,” cites the old CDC vaccine definition.