Vaccination

Vaccination is the administration of a vaccine to stimulate an immune response that helps protect against an infectious disease. It can protect individuals and reduce transmission within populations.

Adaptive immune system: The immune system’s targeted defenses, which recognize specific antigens and can form lasting memory. Vaccination works by prompting this system to recognize a pathogen without requiring the disease itself.
Routine immunization: The scheduled delivery of recommended vaccines to prevent diseases across a population. Routine programs provide vaccination at ages when protection is most useful.
Variolation: An early practice that deliberately exposed people to material from smallpox lesions to induce protection. Variolation preceded vaccination but carried a greater risk of severe disease and transmission.
Passive immunization: Protection provided by transferring ready-made antibodies rather than prompting the recipient to make them. Unlike vaccination, it acts immediately but usually does not create lasting immune memory.
Antigen: A molecule or molecular structure recognized by antibodies or immune-cell receptors. Vaccine antigens provide the specific targets against which immune responses are trained.
Herd immunity: Indirect protection that arises when enough people in a population are immune to limit disease spread. High vaccination coverage can reduce transmission and protect people who are not immune.
Edward Jenner: An English physician whose smallpox inoculation work helped establish vaccination in 1796. Jenner’s cowpox-based approach gave vaccination its name and a safer alternative to variolation.
Natural infection: An infection acquired through exposure to a pathogen rather than through deliberate vaccine administration. Infection can produce immunity, but often at the cost of illness and onward transmission.
Immunological memory: The capacity of immune cells to respond more rapidly or strongly after encountering a previously recognized antigen. This lasting response helps vaccination protect against later exposure to the pathogen.
Vaccination campaign: A coordinated effort to deliver vaccines to a defined population, often within a limited period. Campaigns can rapidly raise coverage during outbreaks or close immunity gaps.

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