Vaccine
Definition
A vaccine is a biological preparation that provides active acquired immunity against a specific infectious disease. It contains weakened, killed, or parts of the pathogen that stimulate the immune system to produce antibodies and memory cells without causing the disease itself.
Key Points for NEET
- 1Provides active immunity (body makes own antibodies)
- 2Types: live attenuated, inactivated, subunit, mRNA
- 3Creates immunological memory
- 4Primary response followed by stronger secondary response
- 5Examples: polio (Sabin, Salk), COVID-19, MMR
Example
MMR vaccine providing immunity against measles, mumps, and rubella
Asked in NEET
Common Mistakes to Avoid
- ✗Confusing active immunity (vaccination, body makes antibodies) with passive immunity (antibody injection, short-lived)
- ✗Thinking vaccines contain live dangerous pathogens — most use killed, attenuated, or subunit forms
- ✗Forgetting that vaccines take time to work — immune memory develops over days to weeks
Quick Revision Notes
- ⚡Types: Live attenuated (MMR, oral polio), Killed (rabies, injectable polio), Subunit (Hepatitis B), mRNA (COVID)
- ⚡Primary response: slow, low IgM; Secondary response (booster): fast, high IgG — due to memory B and T cells
- ⚡Herd immunity: when enough population is vaccinated, even unvaccinated individuals are protected
- ⚡Edward Jenner: first vaccine (smallpox, 1796, using cowpox) — "vacca" = cow in Latin
Related Terms
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More Human Physiology Definitions
Homeostasis
Homeostasis is the ability of an organism or cell to maintain internal stability by adjusting its physiological processes. It involves feedback mechanisms that detect changes and trigger responses to restore optimal conditions. Examples include temperature regulation, blood sugar control, and water balance.
Antibody
An antibody (immunoglobulin) is a Y-shaped protein produced by B cells of the immune system in response to foreign substances (antigens). Antibodies specifically recognize and bind to antigens, marking them for destruction by other immune cells. There are five classes: IgG, IgA, IgM, IgE, and IgD.
Hormone
A hormone is a chemical messenger produced by endocrine glands and transported through the bloodstream to target organs where it regulates physiological processes. Hormones can be proteins, steroids, or amino acid derivatives. They are essential for growth, metabolism, reproduction, and homeostasis.