Immunity and Vaccination
~7 min read
- Two types: Innate (born with) and Acquired (after exposure or vaccination).
- Vaccine: A weakened/killed pathogen that primes immune memory without causing disease.
- Origin: 'Vaccine' from Latin 'vacca' = cow. Edward Jenner introduced immunisation (smallpox, 1796).
The immune system protects us from infection, and vaccines amplify it. CDS/OTA asks about Jenner, vaccine etymology and mechanism.
Types of Immunity
| Type | When acquired | Example |
|---|---|---|
| Innate (natural) | Present from birth — skin, mucus, stomach acid, phagocytes | First-line defence against any pathogen |
| Acquired — Active | Body produces antibodies after natural infection or vaccination | Recovering from chickenpox; BCG vaccine |
| Acquired — Passive | Ready-made antibodies received from outside | Mother's antibodies via placenta/milk; anti-snake venom serum |
How Vaccines Work
- A vaccine introduces a weakened, killed or fragment of pathogen into the body.
- The immune system recognises the antigen and produces specific antibodies and memory cells.
- On real infection later, memory cells produce antibodies quickly and abundantly — preventing or limiting illness.
- Vaccination produces antibodies against the infectious agent — it does NOT block entry of the agent itself or kill it on entry.
- Effective vaccines often need multiple doses (priming + booster) for lasting memory.
History and Etymology
- The word 'vaccination' comes from Latin 'vacca' meaning cow.
- Edward Jenner (1796) noticed that milkmaids who caught cowpox didn't get smallpox. He used cowpox material to immunise — introducing the concept of immunisation to medicine.
- Louis Pasteur developed vaccines against rabies, anthrax — laid foundations of microbiology.
- WHO declared smallpox eradicated in 1980 — the only human disease so removed, entirely by vaccination.
COVID-19 and Indian Vaccine Trials
- The Serum Institute of India was approved by the Drugs Controller General of India (DCGI) to conduct human trials of the Oxford-AstraZeneca (Covishield) vaccine candidate.
- Bharat Biotech developed Covaxin — an inactivated whole-virus vaccine.
- India's COVID-19 vaccination programme delivered over 2 billion doses (mostly Covishield and Covaxin).
CDS/OTA PYQ Examples
Q: The word 'vaccination' is derived from a Latin word relating to:
(a) Pig (b) Horse (c) Cow (d) Dog
Answer: (c) Cow — 'vacca'. [CDS-I 2015]
Q: Who introduced the concept of immunisation?
(a) Edward Jenner (b) Robert Koch (c) Robert Hooke (d) Carl Linnaeus
Answer: (a) Edward Jenner. [CDS-I 2020]
Q: Which institute was approved for human trials of Oxford-AstraZeneca COVID-19 vaccine?
(a) Bharat Biotech (b) AIIMS (c) Serum Institute of India (d) National Institute of Epidemiology
Answer: (c) Serum Institute of India. [CDS-II 2020]
Q: Which statements about vaccination are correct? (1) blocks entry of infectious agent (2) produces antibodies (3) kills agent on entry
(a) 1 only (b) 2 only (c) 2 and 3 only (d) 1, 2 and 3
Answer: (b) 2 only — vaccination produces antibodies. It does not physically block entry or actively kill the agent. [CDS-I 2024]
Drill Immunity and Vaccination for CDS/OTA
CDS/OTA-pattern items on Immunity and Vaccination with answer keys and explanations.
Start Free Mock TestFrequently Asked Questions
What is the difference between vaccine and antibody?
A vaccine is an antigen — primes your body to make its own antibodies. An antibody (immunoglobulin) is the protein that actually neutralises the pathogen. Vaccines trigger active immunity; injected antibodies give passive immunity.
Why do some vaccines need boosters?
Antibody levels and memory cell numbers decline with time. Boosters re-stimulate the immune memory, raising protection back to high levels.
How is herd immunity related to vaccination?
When a high enough fraction of a population is immune (vaccinated or recovered), the pathogen cannot find enough susceptible hosts to spread, indirectly protecting those who can't be vaccinated.