inoculation

Inoculation is the introduction of a substance into a person or organism to stimulate an immune response. In medicine, it usually refers to vaccination—the use of a vaccine to provoke adaptive immunity—though it can also mean passive immunization with ready-made antibodies. The term historically describes deliberate exposure to a pathogen to induce protection, as in variolation.

Historically variolation used material from smallpox lesions; Jenner's 1796 cowpox-based vaccine established safer immunization; subsequent vaccines targeted polio, measles, diphtheria, and more, contributing to disease reduction and eradication possibilities such as smallpox.

How it works and administration: Vaccines introduce antigens or instructions to the immune system without causing disease; B cells produce antibodies and generate memory; T cells participate; protection can be long-lasting. Admin routes include intramuscular, subcutaneous, oral, or nasal; schedules and boosters maintain immunity.

Types: Inactivated (killed organisms), live-attenuated (weakened), toxoid (inactivated toxins), subunit/recombinant, polysaccharide conjugates, and newer platforms like mRNA and viral vectors. Some vaccines provide immediate protection via antibodies (post-exposure prophylaxis).

Public health and safety: Inoculation programs reduce incidence and help achieve herd immunity; safety monitoring detects adverse events; most vaccines have mild short-term side effects; contraindications include severe allergic reactions and certain medical conditions; vaccination decisions are guided by clinical eligibility.