Immunity and Vaccination
NCERT Class 9 • Science • Chapter "Why do we Fall Ill" | NCERT Class 12 • Biology • Chapter "Human Health and Disease"
Immunity and Vaccination
Immunity is the body's ability to resist a pathogen. The body has two layers of defence: a general one present from birth and a specific one that learns from exposure, and vaccination works by training the second without causing the disease.
Types of Immunity
- Innate immunity is present from birth and acts against all pathogens in the same general way.
- It works through physical barriers such as skin and mucous membranes, chemical barriers such as stomach acid and tears, and cells that engulf germs.
- Acquired immunity is specific to a particular pathogen and develops after exposure to it.
- An antigen is any foreign substance that triggers this response; an antibody is the protein made to neutralise it.
- Active immunity develops when the body makes its own antibodies, either after an infection or after vaccination, and it lasts long.
- Passive immunity is acquired ready made, as an infant gets antibodies through mother's milk or a patient gets an injected antiserum, and it is short lived.
- The lymphocytes, a type of white blood cell, carry out the specific immune response and retain a memory of the pathogen.
Vaccination and Its Importance
- A vaccine contains a weakened, killed or partial form of a pathogen that cannot cause the disease but does trigger an immune response.
- The body responds by producing antibodies and memory cells, so a later real infection is met with an immediate defence.
- Edward Jenner developed the first vaccine, against smallpox, and smallpox was later eradicated worldwide.
- India's immunisation programme covers tuberculosis, polio, diphtheria, whooping cough, tetanus, measles, hepatitis B and other diseases.
- Pulse polio campaigns were the key to eliminating polio from India.
- Herd immunity protects even the unvaccinated, because when enough people are immune the chain of transmission breaks.
- Vaccines must be kept cold from manufacture to injection, which is the cold chain.
| Type | How Acquired | Duration |
|---|---|---|
| Active immunity | Body makes its own antibodies | Long lasting |
| Passive immunity | Ready made antibodies received | Short lived |
| Innate immunity | Present from birth | Lifelong, non specific |
Vaccine — a preparation of a weakened or killed pathogen that stimulates immunity without causing the disease.
Hindi me samjhein
सक्रिय प्रतिरक्षा में शरीर स्वयं प्रतिरक्षी बनाता है, इसलिए वह लंबी चलती है। निष्क्रिय प्रतिरक्षा में बने बनाए प्रतिरक्षी मिलते हैं, इसलिए वह जल्दी समाप्त हो जाती है।
Exam me kaise aata hai
- Who developed the first vaccine — Edward Jenner
- The first vaccine was against — smallpox
- Antibodies received ready made give — passive immunity
- Keeping vaccines cold throughout is called the — cold chain
UPSC/State PSC ke liye
- Herd immunity is why a vaccination programme must reach a high share of the population; partial coverage leaves the chain of transmission intact.
- Memory cells explain why a vaccine given once can protect for years, since the response to a later infection is far faster than the first response would have been.
Yahan confuse hote hain
✗ A vaccine cures an existing disease | A vaccine prevents disease by building immunity in advance | ✓
✗ Passive immunity lasts longer than active | Active immunity lasts far longer | ✓
✗ Antigen and antibody mean the same | Antigen triggers the response; antibody neutralises it | ✓
Ek nazar me
- Innate immunity is general and present from birth; acquired immunity is specific.
- Antigen triggers the response and antibody neutralises the pathogen.
- Active immunity is long lasting; passive immunity is short lived.
- Vaccination builds memory cells, and herd immunity protects the community.