Immunology Terms Starting With V

Vaccination is the deliberate administration of a vaccine to induce protective immunity against a specific pathogen or toxin.

Vaccination schedules are designed around the immunological principles of primary and secondary responses, maternal antibody interference, age-dependent immune maturation, and the risk of exposure at different life stages. A primary vaccine dose activates naive B and T cells, while booster doses expand memory cells and raise antibody titers more quickly and to higher levels. Herd protection occurs when enough people are immune that pathogen transmission chains are interrupted, but the threshold varies by pathogen transmissibility, vaccine effectiveness, and population mixing patterns.

Vaccine hesitancy driven by misinformation can lower coverage below protective thresholds, as shown by measles outbreaks in communities where vaccination rates declined despite the availability of an effective vaccine.

Vaccine is a biological preparation that stimulates adaptive immune responses and immunological memory against a specific pathogen or antigen, reducing the risk of future infection, severe disease, or toxin-mediated illness.

Vaccines work by exposing the immune system to antigens in a controlled form that can trigger antibody production, T cell activation, and memory cell generation without requiring the full natural disease. Vaccine platforms include live-attenuated vaccines, inactivated vaccines, subunit and conjugate vaccines, toxoid vaccines, mRNA vaccines, and viral vector vaccines, each presenting antigens in a different immunological context. Live-attenuated vaccines can produce strong, durable immunity because they mimic aspects of natural infection, but they are used cautiously or avoided in severely immunocompromised individuals.

Vaccination is one of the most effective public health interventions in history, having eradicated smallpox globally and drastically reduced disease from measles, polio, diphtheria, and tetanus.

Viral Immunity is the innate and adaptive immune response that detects, contains, and eliminates viral infections through interferons, natural killer cells, antibodies, and virus-specific T cells.

The innate antiviral response is initiated within hours by viral RNA and DNA sensors including RIG-I, MDA5, TLR3, TLR7, and cGAS-STING, which trigger type I interferon production and establish an antiviral state in surrounding cells. Natural killer cells kill virus-infected cells that downregulate MHC class I or display stress ligands before adaptive responses have fully developed. Neutralizing antibodies block viral attachment or entry, while CD8 cytotoxic T cells eliminate infected cells through perforin-granzyme and Fas-FasL pathways once viral peptides are displayed on MHC class I.

Viruses counter these defenses by blocking interferon signaling, hiding in latency, mutating antibody epitopes, or reducing antigen presentation, which is why antiviral immunity often depends on several layers working together.