Science & Technology · Biology · UPSC GS-III
Vaccines — Types, How They Work & Recent Developments 💉
Complete UPSC Notes — made easy for everyone, including non-bio students. 6 vaccine types with visual diagrams, how the immune system learns, COVID-19 vaccine platforms (UPSC 2022!), India's vaccine story, malaria vaccine, mRNA revolution. With PYQs and MCQs.
🛡️ Train Your Army Before War = Vaccine
PYQ: COVID Vaccine Platforms (2022)
PYQ: Recombinant Vector Vaccines (2021)
PYQ: Monoclonal Antibodies (2025)
🇮🇳 AdFalciVax — India's Malaria Vaccine (2025)
mRNA · Viral Vector · Inactivated · Live
Section 01 — Start Here (Zero Biology Knowledge Needed)
🔥 How Do Vaccines Work? — The Simplest Explanation
💡 The "Wanted Poster" Analogy
Imagine your body is a country and your immune system is the army. When a new enemy (virus/bacteria) attacks, your army doesn't recognise it — it takes time to figure out how to fight it. During that time, you get sick. A vaccine is like giving your army a "Wanted Poster" of the enemy before it attacks. Your army studies the poster, trains special soldiers (antibodies), and memorises the enemy's face. Now, when the real enemy shows up, your army recognises it instantly and destroys it before you get sick. That's it. That's how every vaccine works.
The "Wanted Poster" is different for each vaccine type — sometimes it's a dead enemy, sometimes just a photo of the enemy's weapon, sometimes a secret instruction manual. But the goal is always the same: train the immune system before the real attack.
HOW A VACCINE WORKS — Step by Step
① Vaccine Injected"Wanted poster" of enemy given to army
(antigen enters body)
(antigen enters body)
→
② Immune ResponseArmy studies poster, trains special soldiers
(B-cells make antibodies)
(B-cells make antibodies)
→
③ Memory FormedArmy memorises the enemy's face forever
(Memory T & B cells)
(Memory T & B cells)
→
④ Real Attack? No Problem!Army recognises enemy instantly & destroys it
YOU DON'T GET SICK ✓
YOU DON'T GET SICK ✓
📌 Key Terms Made Simple: Antigen = the "Wanted Poster" — a piece of the enemy that your immune system learns to recognise. Antibody = the weapon your B-cells make to destroy the enemy. Memory cells = soldiers that remember the enemy for years/decades. Immune response = the whole process of recognising, fighting, and remembering. Different vaccine types use different kinds of Wanted Posters — that's what the next section is about.
Section 02 — Very Important
💉 6 Types of Vaccines — With Visual Diagrams
1. Live Attenuated Vaccines
Weakened live pathogenDANGEROUS virus
→
Weaken in lab
→
WEAKENED virus
→
Inject
→
Strong, long-lasting immunity ✓
Mimics real infection
Mimics real infection
How it works: Uses a live but weakened version of the actual virus/bacteria. It can replicate but cannot cause disease in healthy people. Gives strong, long-lasting immunity (often lifelong) because the immune system sees the whole pathogen.
Examples: MMR (measles, mumps, rubella), OPV (Oral Polio), BCG (tuberculosis), Yellow Fever, Rotavirus, Chickenpox (Varicella)
✓ Strong immunity✓ Often 1-2 doses✗ Not for immunocompromised✗ Needs cold storage
2. Inactivated (Killed) Vaccines
Dead pathogenLive virus
→
Kill with heat/
chemicals
chemicals
→
DEAD virus
→
Inject
→
Safer but weaker
Needs booster doses
Needs booster doses
How it works: The virus/bacteria is killed (using heat, chemicals, or radiation) before injection. The dead pathogen cannot replicate or cause disease, making it very safe. But because it's dead, the immune response is weaker — so booster doses are needed.
Examples: COVAXIN (COVID-19), IPV (Injectable Polio), Hepatitis A, Rabies, Flu shot (some types)
✓ Very safe✓ Easier storage✗ Weaker immunity✗ Needs boosters
3. Subunit / Recombinant / Protein Vaccines
Only a piece of the pathogenWhole virus
→
Extract spike
protein only
protein only
→
Just the "key"
(spike protein)
(spike protein)
→
Inject
→
Very safe — no virus at all, just a piece
How it works: Instead of the whole virus, only a specific protein or piece of the pathogen is used (e.g., the spike protein of COVID-19). Made using rDNA technology — the protein is manufactured in yeast or bacteria. Very safe because there's no virus at all.
Examples: Hepatitis B, HPV (cervical cancer), Corbevax (COVID-19), Pertussis (whooping cough — acellular), Novavax (COVID-19)
✓ Very safe✓ Safe for immunocompromised✗ May need adjuvant✗ Needs boosters
4. Viral Vector Vaccines — Asked in UPSC 2021 & 2022!
Harmless virus delivers instructionsCOVID spike gene
+
Harmless adenovirus
(delivery truck)
(delivery truck)
→
Vector enters
your cells
your cells
→
Cells make
spike protein
spike protein
→
IMMUNITY ✓
How it works: A harmless virus (adenovirus) is modified to carry the gene for the pathogen's protein (like COVID spike). This "delivery truck" enters your cells, which then produce the spike protein. Your immune system sees the protein and mounts a response. The vector virus cannot cause disease.
Examples: Covishield/AstraZeneca = viral vector (NOT mRNA!), Sputnik V = viral vector, Johnson & Johnson, Ebola vaccine. Uses adenovirus as the delivery truck.
✓ Strong immune response✓ Proven technology✗ Pre-existing immunity to vector
⚠️ UPSC 2022 Trap: Covishield is a VIRAL VECTOR vaccine (adenovirus-based), NOT mRNA. Many candidates confused this. Statement "Covishield uses mRNA platform" was WRONG. Remember: Covishield = AstraZeneca = chimpanzee adenovirus vector.
5. mRNA Vaccines — The New Revolution
Instructions only, no virusmRNA "recipe"
for spike protein
for spike protein
→
Wrapped in lipid
nanoparticle (LNP)
nanoparticle (LNP)
→
Cell reads recipe,
makes spike protein
makes spike protein
→
Immune system learns
mRNA degrades in hours
mRNA degrades in hours
How it works: Instead of any virus, the vaccine contains mRNA — a "recipe" that tells your cells how to make the spike protein. Wrapped in a tiny lipid nanoparticle (LNP) for delivery. Your cell reads the recipe, makes the spike protein, displays it, and the immune system attacks it. The mRNA degrades within hours — it does NOT change your DNA.
Examples: Pfizer-BioNTech (Comirnaty), Moderna (Spikevax). India: Gennova developing self-amplifying mRNA (saRNA) platform for Nipah.
✓ Rapid development✓ Easily updated for variants✓ No virus used✗ Needs ultra-cold storage (-70°C)
6. Toxoid Vaccines
Inactivated toxinHow it works: Some bacteria cause disease through toxins (poisons), not through the bacteria itself. Toxoid vaccines contain an inactivated version of the toxin. The immune system learns to fight the toxin, not the bacterium. The toxoid cannot cause disease.
Examples: Tetanus (TT), Diphtheria. Both in the DPT vaccine.
✓ Very safe✓ Well-established✗ Needs boosters every 10 years
Section 03 — UPSC PYQ 2022 Topic!
🦠 COVID-19 Vaccines — Platform Comparison
⚠️ Exam Trap (UPSC 2022): "Covishield uses mRNA platform" — this is WRONG. Covishield is a viral vector vaccine (adenovirus-based). Many candidates got this wrong. Memorise the table below!
| Vaccine | Platform | Developer | How It Works |
|---|---|---|---|
| Covishield | Viral Vector (NOT mRNA!) | AstraZeneca + Oxford → Serum Institute of India | Modified chimpanzee adenovirus carries spike gene |
| Sputnik V | Viral Vector | Gamaleya Institute (Russia) | Human adenovirus vectors (Ad26 + Ad5) |
| COVAXIN | Inactivated (Killed) | Bharat Biotech + ICMR (India) | Whole SARS-CoV-2 virus killed with β-propiolactone |
| Pfizer/BioNTech | mRNA | Pfizer + BioNTech (USA/Germany) | mRNA in lipid nanoparticles → cells make spike protein |
| Moderna | mRNA | Moderna (USA) | mRNA in lipid nanoparticles → cells make spike protein |
| Corbevax | Protein Subunit | Biological E (India) | Recombinant spike protein produced in yeast |
| Novavax | Protein Subunit | Novavax (USA) | Spike protein nanoparticles + Matrix-M adjuvant |
| J&J (Janssen) | Viral Vector | Johnson & Johnson (USA) | Human adenovirus (Ad26) carries spike gene |
Section 04 — Current Affairs
🆕 Recent Vaccine Developments (2025–26)
🦟 India's Malaria Vaccine (2025)
ICMR licensed AdFalciVax — India's first indigenous multi-stage malaria recombinant vaccine — to 5 Indian companies (Sep 2025). Targets P. falciparum. Supports India's goal of malaria elimination by 2030.
🌍 WHO Malaria Vaccines
RTS,S/AS01 (Mosquirix) — WHO approved 2021. R21/Matrix-M — WHO approved 2023. Both target children under 5 in endemic Africa. First-ever malaria vaccines.
🧬 mRNA Beyond COVID
mRNA platform being developed for: malaria, universal flu, Nipah, cancer. India's Gennova received $13.38M from CEPI (Mar 2025) for self-amplifying mRNA (saRNA) vaccine for Nipah virus.
🦟 Dengue Vaccine
Takeda's Qdenga (dengue vaccine) aims to launch in India in 2026 via collaboration with Biological E under Make in India initiative.
Section 05 — Previous Year Questions
🧾 UPSC PYQs on Vaccines
In the context of vaccines manufactured to prevent COVID-19 pandemic, consider the following statements:
Which of the statements given above are correct?
1.The Serum Institute of India produced COVID-19 vaccine named Covishield using mRNA platform.
2.Sputnik V vaccine is manufactured using vector-based platform.
3.COVAXIN is an inactivated pathogen-based vaccine.
A1 and 2 only
B2 and 3 only
C1 and 3 only
D1, 2 and 3
📌 Explanation
Answer: (b) 2 and 3 only.
Statement 1 ✗ — Covishield does NOT use mRNA. It uses viral vector platform (modified chimpanzee adenovirus ChAdOx1). Developed by AstraZeneca/Oxford, manufactured by Serum Institute of India.
Statement 2 ✓ — Sputnik V uses vector-based platform (human adenovirus Ad26 + Ad5).
Statement 3 ✓ — COVAXIN is inactivated pathogen-based (whole killed SARS-CoV-2 virus). Made by Bharat Biotech + ICMR.
Answer: (b) 2 and 3 only.
Statement 1 ✗ — Covishield does NOT use mRNA. It uses viral vector platform (modified chimpanzee adenovirus ChAdOx1). Developed by AstraZeneca/Oxford, manufactured by Serum Institute of India.
Statement 2 ✓ — Sputnik V uses vector-based platform (human adenovirus Ad26 + Ad5).
Statement 3 ✓ — COVAXIN is inactivated pathogen-based (whole killed SARS-CoV-2 virus). Made by Bharat Biotech + ICMR.
With reference to recent developments regarding 'Recombinant Vector Vaccines', consider the following statements:
Which of the statements given above is/are correct?
1.Genetic engineering is applied in the development of these vaccines.
2.Bacteria and viruses are used as vectors.
A1 only
B2 only
CBoth 1 and 2
DNeither 1 nor 2
📌 Explanation
Answer: (c) Both 1 and 2.
1 ✓ — Recombinant vector vaccines use genetic engineering to insert pathogen genes into harmless vectors.
2 ✓ — Both bacteria and viruses can serve as vectors. Adenovirus vectors were used in Covishield, Sputnik V, J&J. Bacterial vectors are also used in some experimental vaccines.
Answer: (c) Both 1 and 2.
1 ✓ — Recombinant vector vaccines use genetic engineering to insert pathogen genes into harmless vectors.
2 ✓ — Both bacteria and viruses can serve as vectors. Adenovirus vectors were used in Covishield, Sputnik V, J&J. Bacterial vectors are also used in some experimental vaccines.
With reference to monoclonal antibodies, often mentioned in news, consider the following statements:
Which of the statements given above are correct?
I.They are man-made proteins.
II.They stimulate immunological function due to their ability to bind to specific antigens.
III.They are used in treating viral infections like that of Nipah virus.
AI and II only
BII and III only
CI and III only
DI, II and III
📌 Explanation
Answer: (d) All three correct.
I ✓ — mAbs are lab-made proteins (Hybridoma technology).
II ✓ — They bind to specific antigens → guide/enhance immune response.
III ✓ — Used against COVID-19, Ebola, and Nipah virus (m102.4 monoclonal antibody).
Note: mAbs are different from vaccines — vaccines prevent disease; mAbs treat active infections.
Answer: (d) All three correct.
I ✓ — mAbs are lab-made proteins (Hybridoma technology).
II ✓ — They bind to specific antigens → guide/enhance immune response.
III ✓ — Used against COVID-19, Ebola, and Nipah virus (m102.4 monoclonal antibody).
Note: mAbs are different from vaccines — vaccines prevent disease; mAbs treat active infections.
Section 06 — Practice
📝 UPSC-Style MCQs
Q1Which vaccine type uses a harmless virus to deliver genetic material from the target pathogen into the body?
a) Inactivated vaccine
b) Viral vector vaccine
c) mRNA vaccine
d) Toxoid vaccine
Viral vector vaccines use a modified harmless virus (like adenovirus) to carry the target pathogen's gene into the body. Examples: Covishield, Sputnik V. mRNA vaccines use synthetic RNA instructions (no virus at all). Answer: (b).
Q2Which of the following COVID-19 vaccines uses an inactivated (killed) pathogen platform?
a) Covishield
b) Pfizer-BioNTech
c) COVAXIN
d) Sputnik V
COVAXIN (Bharat Biotech + ICMR) is the inactivated pathogen vaccine — the whole SARS-CoV-2 virus is killed. Covishield and Sputnik V are viral vector. Pfizer is mRNA. Answer: (c).
Q3Consider the following:
1. mRNA vaccines contain a live virus.
2. mRNA vaccines can alter human DNA.
3. mRNA degrades within hours after producing the target protein.
Which is/are correct?
1. mRNA vaccines contain a live virus.
2. mRNA vaccines can alter human DNA.
3. mRNA degrades within hours after producing the target protein.
Which is/are correct?
a) 1 and 2 only
b) 3 only
c) 2 and 3 only
d) 1, 2 and 3
Only statement 3 is correct. (1) mRNA vaccines contain NO virus — only synthetic RNA instructions. (2) mRNA does NOT alter DNA — it never enters the cell nucleus where DNA is stored. (3) mRNA degrades within hours ✓. Answer: (b).
Section 07
🧠 Memory Aid
🔑 Lock These In for Prelims Day
VACCINE
"Wanted poster" for your immune army. Trains the body to fight BEFORE the real attack. Contains antigen → triggers antibodies + memory cells.
LIVE
Weakened live pathogen. Strong, long-lasting immunity. NOT for immunocompromised. Examples: MMR, OPV, BCG, Yellow Fever.
KILLED
Dead pathogen. Safe but weaker — needs boosters. Examples: COVAXIN, IPV, Hepatitis A, Rabies.
SUBUNIT
Only a protein piece. Very safe. Made by rDNA. Examples: Hepatitis B, HPV, Corbevax, Novavax.
VECTOR
Harmless virus delivers target gene. Examples: Covishield (chimp adenovirus), Sputnik V (human adenovirus), J&J. NOT mRNA!
mRNA
Synthetic RNA instructions in LNPs. No virus. Degrades in hours. Does NOT alter DNA. Examples: Pfizer, Moderna. India: Gennova saRNA.
TOXOID
Inactivated toxin (not pathogen). Examples: Tetanus, Diphtheria. In the DPT vaccine.
PYQ 2022
Covishield = vector (NOT mRNA!) ✗. Sputnik V = vector ✓. COVAXIN = inactivated ✓. Answer: (b) 2 and 3.
MALARIA
RTS,S (WHO 2021), R21/Matrix-M (WHO 2023). India: AdFalciVax (ICMR, Sep 2025). mRNA malaria vaccine in trials.
mAbs
Monoclonal antibodies ≠ vaccines. Man-made proteins. Treat infections (COVID, Ebola, Nipah). Hybridoma tech. UPSC 2025!
Section 08
❓ FAQs
Can mRNA vaccines alter my DNA?
No. This is a common myth. mRNA never enters the cell nucleus where DNA is stored. It stays in the cytoplasm, instructs ribosomes to make the spike protein, and then degrades within hours. mRNA cannot integrate into DNA — it doesn't have the enzymes needed for that (reverse transcriptase). Your DNA remains completely unchanged. Think of mRNA as a sticky note with a temporary instruction — it dissolves after the task is done.
What is the difference between a vaccine and a monoclonal antibody?
Vaccine = preventive. Given BEFORE infection. Trains YOUR immune system to make its own antibodies. Protection lasts years/decades. Monoclonal antibody (mAb) = therapeutic. Given DURING/AFTER infection. Pre-made antibodies injected from outside. Provides immediate but temporary protection (weeks/months). Think of vaccines as teaching someone to fish vs mAbs as giving them a fish.
Why does India make so many vaccines?
India is called the "Vaccine Capital of the World". The Serum Institute of India alone produces ~1.5 billion vaccine doses per year — more than any other facility globally. Key factors: (1) Low manufacturing costs. (2) Skilled workforce in biotechnology. (3) Government support (National Biopharma Mission, BioPharma SHAKTI). (4) Strong regulatory framework (CDSCO). (5) Historical investments — India has supplied DPT, BCG, and measles vaccines globally for decades. India supplies vaccines to 170+ countries and was central to COVID-19 vaccine production globally.
Section 09 — Mains
📜 Probable Mains Questions
Probable Question 1
"Discuss the different types of vaccine platforms. How did the COVID-19 pandemic accelerate vaccine technology innovation?"
Probable Question 2
"India is often called the 'Vaccine Capital of the World.' Discuss India's contributions to global vaccine production and the significance of schemes like BioPharma SHAKTI."
Section 10
🏁 Conclusion
💉 From Smallpox to mRNA — The Vaccine Revolution
In 1796, Edward Jenner used cowpox to protect against smallpox — the world's first vaccine. Two centuries later, scientists designed a vaccine against COVID-19 in just 2 days (Moderna's mRNA sequence was finalised on January 13, 2020, just two days after China shared the virus's genetic sequence). Between these two moments lies the entire arc of vaccine science: from live attenuated to inactivated, from subunit to viral vector, from protein to mRNA.
For UPSC, the COVID-19 pandemic turned vaccine technology into a high-frequency exam topic. The 2021 question tested recombinant vector vaccines. The 2022 question tested COVID vaccine platforms (and trapped candidates who confused Covishield with mRNA). The 2025 question tested monoclonal antibodies. The pattern is clear: know the platforms, know the Indian examples, know the differences.
The one line to remember: Covishield = VIRAL VECTOR (not mRNA). COVAXIN = INACTIVATED. Pfizer/Moderna = mRNA. Sputnik V = VIRAL VECTOR. Corbevax = PROTEIN SUBUNIT. This single table has been worth 2 marks in UPSC Prelims.
