Public healh scientists and leaders cite a number of reasons to encourage as many members of a community as possible to get vaccinatons against serious communicable diseases.
No vaccination offers 100% protection, so having more people vaccinated helps reduce the risk of serious illness for all.
Some members of the population—infants, children, the immunocompromised—may not be able to gain adequate protection from a vaccine, so hope to rely on widespread vaccinations of others to reduce their own risk.
The goal of “herd immunity” reflects these considerations, which have prevailed in the U.S. since court decisions in the early 20th century upholding authorities’ power to make certain vaccinations mandatory.
The goal underlies continuing efforts to inoculate more people against COVID-19, despite objections based on personal preference, religious grounds or claims of immunity acquired through previous infection.