UPSC CSE Prelims
Vaccines and Immunization Previous Year Questions (PYQs)

Detailed Explanation:

Monoclonal antibodies (mAbs) are laboratory-made proteins designed to recognize and bind to a specific antigen.

• Statement I is Correct: They are man-made proteins produced in laboratories.

• Statement II is Correct: They bind to specific antigens and help the immune system identify or neutralize harmful pathogens.

• Statement III is Correct: Monoclonal antibodies are used in treating and preventing certain viral infections, including the Nipah virus.

• Therefore, all three statements are correct, making Option D the correct answer.

Statement-wise Analysis

Notes: Monoclonal Antibodies (mAbs)

What are Monoclonal Antibodies?

Monoclonal antibodies are identical laboratory-produced antibodies designed to target a specific antigen.

How do they work?

• Bind to a specific antigen.

• Block pathogens from infecting cells.

• Help the immune system destroy infected or abnormal cells.

Major Uses

• Cancer treatment

• Autoimmune diseases

• Viral infections (COVID-19, Ebola, Nipah)

• Diagnostic tests

Important Facts

• Developed using a single clone of immune cells, hence the term "monoclonal."

• They are highly specific compared to conventional drugs.

• Widely used in modern biotechnology and precision medicine.

Detailed Explanation:

Answer: Option 2 — 2 and 3 only

This question tests knowledge about different COVID-19 vaccine platforms used in India. Statement 1 is incorrect because Covishield is a viral vector vaccine (using chimpanzee adenovirus), not an mRNA vaccine. Statements 2 and 3 are correct as they accurately describe the platforms used for Sputnik V and COVAXIN respectively.

❌ Statement 1 – Incorrect: Covishield is a viral vector vaccine using chimpanzee adenovirus (ChAdOx1), not an mRNA platform vaccine.
✅ Statement 2 – Correct: Sputnik V uses a vector-based platform with two different human adenovirus vectors (rAd26 and rAd5) in a two-dose regimen.
✅ Statement 3 – Correct: COVAXIN, developed by Bharat Biotech, is an inactivated pathogen-based vaccine using the whole-virion inactivated Vero cell platform.

📝 Short Notes: COVID-19 Vaccine Platforms

Detailed Explanation:

Answer: Option 3 — Both 1 and 2

Recombinant vector vaccines utilize genetic engineering to insert pathogen genes into harmless carrier organisms (vectors), which then deliver these genes into human cells to produce antigens and trigger immunity. Both viruses (like Adenoviruses in Covishield) and bacteria (like attenuated Salmonella or BCG) can serve as vectors in these vaccines.

✅ Statement 1 – Correct: Genetic engineering is essential for developing recombinant vector vaccines, involving the insertion of pathogen antigen genes into a vector's genetic material.
✅ Statement 2 – Correct: Both bacteria (e.g., Salmonella, BCG) and viruses (e.g., Adenovirus, VSV) are used as vectors to deliver antigens.

📝 Short Notes: Recombinant Vector Vaccines

• Technology: Uses genetic engineering to insert genes encoding pathogen antigens into harmless viral or bacterial vectors
• Mechanism: Vectors deliver genetic material into host cells, which then produce antigens triggering immune response
• Viral Vectors: Adenoviruses (Covishield/Sputnik V), Vesicular Stomatitis Virus (Ebola vaccine - Ervebo), Modified Vaccinia Ankara (MVA)
• Bacterial Vectors: Attenuated Salmonella typhimurium, Mycobacterium bovis (BCG), Listeria monocytogenes strains
• Advantages: Strong cellular and humoral immunity, no live pathogen used, scalable production
• Examples: COVID-19 vaccines (AstraZeneca/Covishield, J&J, Sputnik V), Ebola vaccine (Ervebo), experimental TB and malaria vaccines

Detailed Explanation:

Answer: Option 4 — spread of viral diseases

ACE2 (Angiotensin-Converting Enzyme 2) is a protein receptor found on human cell surfaces that became widely discussed during the COVID-19 pandemic. The SARS-CoV-2 virus uses ACE2 as its primary entry point into human cells, binding to this receptor through its spike protein to infect cells in the lungs, heart, kidneys, and other organs.

📝 Short Notes: ACE2 Receptor

• Full Form: Angiotensin-Converting Enzyme 2
• Normal Function: ACE2 is an enzyme that plays a crucial role in regulating blood pressure and cardiovascular function by converting angiotensin II to angiotensin (1-7)
• Location: Found on cell surfaces in multiple organs including lungs (alveolar cells), heart, kidneys, intestines, and blood vessels
• Role in COVID-19: Acts as the cellular receptor that SARS-CoV-2 spike protein binds to for viral entry into cells
• Research Significance: Target for therapeutic interventions including soluble ACE2, monoclonal antibodies, and small molecule inhibitors to block viral entry
• Previous Connection: The original SARS-CoV virus (2003) also used ACE2 as its receptor, making it a known vulnerability in coronavirus infections

Detailed Explanation:

Answer: Option 2 — 1 and 2 only

Pneumococcal Conjugate Vaccines (PCVs) are crucial in India's immunization program as they protect against multiple serious diseases caused by Streptococcus pneumoniae and help combat antibiotic resistance. Statement 3 is incorrect as no vaccine is completely free from side effects or allergic reactions.

✅ Statement 1 – Correct: PCVs are highly effective against pneumonia, meningitis (inflammation of brain and spinal cord membranes), and sepsis (blood infection) caused by Streptococcus pneumoniae bacteria.
✅ Statement 2 – Correct: PCVs reduce dependence on antibiotics by preventing pneumococcal infections, thereby addressing the growing problem of antibiotic-resistant bacterial strains.
❌ Statement 3 – Incorrect: Like all vaccines, PCVs can cause mild side effects (redness, swelling, soreness at injection site) and rare allergic reactions; no vaccine is completely side-effect-free.

📝 Short Notes: Pneumococcal Conjugate Vaccines (PCVs)

• Causative Organism: Streptococcus pneumoniae (pneumococcus) — a bacterium with over 90 serotypes.
• Diseases Prevented: Pneumonia, meningitis, sepsis, otitis media (ear infection), and bacteremia.
• Types of Vaccines: PCV10 (protects against 10 serotypes) and PCV13 (protects against 13 serotypes).
• India's Immunization Program: PCV introduced in Universal Immunization Programme (UIP) in 2017; given at 6, 10, and 14 weeks of age.
• Public Health Impact: Reduces child mortality, prevents pneumococcal diseases (leading cause of death in children under 5), and decreases antibiotic use.
• Antibiotic Resistance: PCVs help combat drug-resistant pneumococcal strains by preventing infections, reducing need for antibiotics.
• Common Side Effects: Mild reactions like fever, irritability, injection site reactions; serious allergic reactions are rare but possible.

Detailed Explanation:

Answer: Option 2 — Hepatitis B, unlike Hepatitis C, does not have a vaccine.

This statement is incorrect because a highly effective vaccine for Hepatitis B has been available since 1982, whereas no vaccine exists for Hepatitis C. The question asks for the statement that is NOT correct.

✅ Statement 1 – Correct: Hepatitis B virus is transmitted through similar routes as HIV (blood contact, sexual contact, mother-to-child transmission).
❌ Statement 2 – Incorrect: Hepatitis B has a vaccine; Hepatitis C does not have a vaccine.
✅ Statement 3 – Correct: Globally, Hepatitis B and C infections combined far exceed HIV infections (approximately 325 million vs 38 million).
✅ Statement 4 – Correct: Chronic Hepatitis B and C infections can remain asymptomatic for many years before causing liver damage.

📝 Short Notes: Hepatitis B & C