Vaccine and Vaccination — MCQs

Vaccine and Vaccination Indian Medical PG Practice Questions and MCQs

Question 11: For which of the following diseases are live vaccines used?

A. Measles
B. Cholera
C. Small pox
D. All of the above (Correct Answer)

Explanation: **Explanation:** The correct answer is **D (All of the above)** because Measles, Cholera, and Smallpox all have versions that utilize live-attenuated microorganisms to induce immunity. 1. **Measles (Option A):** The measles vaccine is a classic example of a **live-attenuated viral vaccine**. It is typically administered as part of the MMR (Measles, Mumps, Rubella) or MR vaccine. It induces both humoral and cell-mediated immunity, mimicking a natural infection without causing the disease. 2. **Cholera (Option B):** While parenteral killed vaccines were used historically, the modern **Oral Cholera Vaccines (OCV)** include live-attenuated strains (e.g., **Vaxchora** using the *Vibrio cholerae* CVD 103-HgR strain). Note: Killed oral vaccines like Shanchol are also common, but the existence of a live version makes this option correct in a multiple-choice context. 3. **Smallpox (Option C):** The smallpox vaccine (Variola vaccine) uses the **live Vaccinia virus**. It is the most successful vaccine in history, leading to the global eradication of smallpox in 1980. **Clinical Pearls for NEET-PG:** * **Mnemonic for Live Vaccines:** "**B**oy **R**omeo **G**ive **M**y **L**ove **S**picy **V**ictory **T**onight" (**B**CG, **R**otavirus, **G**umbaro/not for humans, **M**MR, **L**ive Typhoid/Ty21a, **S**mallpox, **V**aricella/VZV, **T**yellow fever). * **Contraindications:** Live vaccines are generally contraindicated in **pregnancy** and **immunocompromised** individuals (HIV with low CD4 counts, chemotherapy, etc.) due to the risk of uncontrolled viral replication. * **Storage:** Most live vaccines are heat-sensitive and must be stored in the **Deep Freezer** (e.g., OPV, Measles) at the district level to maintain potency.

Question 12: Which of the following is not a live vaccine?

A. BCG
B. OPV
C. Measles
D. Tetanus (Correct Answer)

Explanation: ### Explanation The correct answer is **D. Tetanus**. **1. Why Tetanus is the correct answer:** Vaccines are broadly classified into live-attenuated, killed (inactivated), toxoids, and subunit vaccines. **Tetanus** is a **toxoid vaccine**. It is prepared by treating the exotoxin produced by *Clostridium tetani* with formaldehyde, which renders it non-toxic while preserving its immunogenicity. It does not contain live organisms. **2. Analysis of Incorrect Options:** * **A. BCG (Bacillus Calmette-Guérin):** This is a **live-attenuated** bacterial vaccine derived from *Mycobacterium bovis*. It is the only live bacterial vaccine routinely used in the National Immunization Schedule. * **B. OPV (Oral Polio Vaccine/Sabin):** This is a **live-attenuated** viral vaccine. It induces both systemic (IgG) and local mucosal (IgA) immunity. (Note: IPV/Salk is the killed version). * **C. Measles:** This is a **live-attenuated** viral vaccine (Edmonston-Zagreb strain). It is typically administered at 9 months of age in India. **3. NEET-PG High-Yield Clinical Pearls:** * **Mnemonic for Live Vaccines:** "**B**oy **R**eally **I**s **V**ery **S**mart **Y**et **M**akes **M**any **L**ittle **T**yping **P**errors" (**B**CG, **R**otavirus, **I**ntranasal Influenza, **V**aricella, **S**abin/OPV, **Y**ellow Fever, **M**easles, **M**umps, **L**ive Typhoid/Ty21a, **P**lague). * **Contraindication:** Live vaccines are generally contraindicated in **pregnancy** and **immunocompromised** states (except HIV patients before the symptomatic stage, where BCG/Measles may be given based on CD4 counts). * **Storage:** Most live vaccines are heat-sensitive and must be stored in the **ILR (Ice-Lined Refrigerator)** at +2°C to +8°C; however, OPV is the most heat-sensitive and is stored at -20°C for long-term stability.

Question 13: What type of vaccine is currently used against hepatitis B infection?

A. Killed pooled serum
B. Live attenuated
C. Recombinant (Correct Answer)
D. Synthetic vaccine

Explanation: **Explanation:** The Hepatitis B vaccine is a **Recombinant Subunit Vaccine**. It is produced using genetic engineering technology where the gene coding for the **Hepatitis B surface antigen (HBsAg)** is inserted into common baker’s yeast (*Saccharomyces cerevisiae*). The yeast cells then express and produce large quantities of HBsAg, which are harvested, purified, and used as the immunizing agent. This induces the production of protective **Anti-HBs antibodies**. **Analysis of Options:** * **A. Killed pooled serum:** Historically, the first-generation HBV vaccine (Heptavax) was derived from the plasma of chronic carriers. However, this was discontinued in the 1980s due to risks of contamination with live blood-borne pathogens (like HIV). * **B. Live attenuated:** There is no live-attenuated vaccine for Hepatitis B. Because HBV is a DNA virus associated with chronic carriage and hepatocellular carcinoma, using a live version poses significant safety risks. * **C. Recombinant (Correct):** This is the current "second-generation" vaccine. It is safe, contains no viral DNA, and cannot cause infection. * **D. Synthetic vaccine:** While research into synthetic peptide vaccines exists, they are not currently used in clinical practice for HBV. **Clinical Pearls for NEET-PG:** * **Schedule:** Given at 0, 1, and 6 months. * **Site:** Intramuscular (IM) injection in the **Deltoid** (adults) or **Anterolateral thigh** (infants). It should *never* be given in the gluteal region as the fat reduces vaccine efficacy. * **Non-responders:** Individuals who fail to develop an adequate antibody titer (>10 mIU/mL) after a complete series. * **Universal Immunization Program (UIP):** In India, the birth dose is crucial to prevent vertical transmission.

Question 14: Which of the following is NOT a live attenuated vaccine?

A. Oral polio vaccine
B. Yellow fever vaccine
C. Measles vaccine
D. Influenza vaccine (Correct Answer)

Explanation: **Explanation:** The correct answer is **D. Influenza vaccine**. In the context of standard medical examinations like NEET-PG, the "Influenza vaccine" typically refers to the **Inactivated Influenza Vaccine (IIV)**, which is administered intramuscularly. While a Live Attenuated Influenza Vaccine (LAIV) exists as a nasal spray, the injectable form used in routine practice is a killed/subunit vaccine. **Why Option D is correct:** Live attenuated vaccines contain pathogens that are weakened but still capable of replicating within the host to induce an immune response. The standard injectable Influenza vaccine consists of inactivated (killed) virus or specific viral proteins (surface antigens), making it safe for immunocompromised individuals and pregnant women. **Why other options are incorrect:** * **A. Oral Polio Vaccine (Sabin):** A classic live attenuated vaccine. It replicates in the gut to provide local IgA immunity. (Note: The Salk/IPV is the inactivated version). * **B. Yellow Fever Vaccine:** Uses the **17D strain**, which is a highly effective live attenuated virus. * **C. Measles Vaccine:** Part of the MMR/MR complex, this is a live attenuated viral vaccine (Edmonston-Zagreb or Schwarz strain). **High-Yield Clinical Pearls for NEET-PG:** 1. **Mnemonic for Live Vaccines:** "**Rome Is My Best Place Yell**" (**R**ubella, **O**ral Polio/OPV, **M**easles/Mumps, **E**pizootic Typhus, **I**nfluenza (nasal), **S**mallpox, **M**ycobacterium bovis/BCG, **B**elgian Typhoid/Ty21a, **P**lague, **Y**ellow Fever). 2. **Contraindications:** Live vaccines are generally contraindicated in **pregnancy** and **immunocompromised** states (HIV with low CD4 count) due to the risk of uncontrolled viral replication. 3. **Yellow Fever:** It is the only vaccine that requires an International Certificate of Vaccination for travel to specific endemic zones.

Question 15: Which types of HPV vaccines are available?

A. Monovalent
B. Trivalent
C. Bivalent and Quadrivalent (Correct Answer)
D. Quadrivalent

Explanation: **Explanation:** Human Papillomavirus (HPV) vaccines are designed to prevent cervical cancer, anogenital warts, and other HPV-associated malignancies. Currently, three main types of recombinant vaccines have been developed globally, though the **Bivalent** and **Quadrivalent** versions are the most traditionally recognized in clinical practice and examinations. * **Why Option C is Correct:** 1. **Bivalent Vaccine (Cervarix):** Targets HPV types **16 and 18**, which are responsible for approximately 70% of cervical cancer cases. 2. **Quadrivalent Vaccine (Gardasil):** Targets HPV types **6, 11, 16, and 18**. Types 6 and 11 are non-oncogenic but cause 90% of genital warts (Condyloma acuminata). *Note: A 9-valent vaccine (Gardasil 9) is also now available, covering five additional oncogenic types (31, 33, 45, 52, 58).* * **Why Other Options are Incorrect:** * **Monovalent (A) & Trivalent (B):** There are no commercially available monovalent or trivalent HPV vaccines. The minimum coverage starts with the two most high-risk types (16 and 18). * **Quadrivalent (D):** While correct, it is incomplete as the bivalent vaccine is also a standard available preparation. **High-Yield Clinical Pearls for NEET-PG:** * **Vaccine Type:** These are **Subunit vaccines** containing **Virus-Like Particles (VLPs)** prepared using recombinant DNA technology (L1 protein). * **Dosage Schedule:** * 9–14 years: 2 doses (0, 6 months). * >15 years or immunocompromised: 3 doses (0, 1–2, 6 months). * **Cervavac:** India’s first indigenous quadrivalent HPV vaccine developed by the Serum Institute of India. * **Target Age:** Ideally administered before the onset of sexual activity (recommended age 9–14 years).

Question 16: What is the role of an adjuvant in a DPT vaccine?

A. Decrease hypersensitivity
B. Decrease absorption of vaccine
C. Increase antigenicity (Correct Answer)
D. Increase the shelf life of a vaccine

Explanation: ### Explanation **Correct Option: C. Increase antigenicity** Adjuvants (from the Latin *adjuvare*, meaning "to help") are substances added to vaccines to enhance the body's immune response to an antigen. In the DPT (Diphtheria, Pertussis, and Tetanus) vaccine, the adjuvant used is typically an aluminum salt (e.g., aluminum phosphate or aluminum hydroxide). The underlying medical concept is the **"Depot Effect."** The adjuvant slows down the release of the antigen from the injection site, providing a prolonged stimulus to the immune system. It also recruits antigen-presenting cells (APCs) and stimulates the release of cytokines, thereby **increasing the overall antigenicity** and ensuring a more robust and long-lasting production of antibodies. **Analysis of Incorrect Options:** * **A. Decrease hypersensitivity:** Adjuvants do not decrease hypersensitivity; in fact, they can sometimes cause local injection site reactions (redness or swelling) due to the heightened immune activation. * **B. Decrease absorption of vaccine:** While adjuvants do slow the *clearance* of the antigen (the depot effect), the goal is not to hinder absorption but to optimize the immune system's exposure to the antigen. * **D. Increase the shelf life:** Substances that increase shelf life are called **preservatives** (e.g., Thiomersal) or **stabilizers**, not adjuvants. --- ### High-Yield Clinical Pearls for NEET-PG * **Common Adjuvants:** Aluminum salts (Alum) are the most common. Others include MF59 (oil-in-water emulsion) and AS04. * **Live Vaccines:** Generally, **live attenuated vaccines do not require adjuvants** because they replicate and naturally trigger a strong immune response. Adjuvants are primarily used in killed (inactivated) or subunit/toxoid vaccines. * **DPT Storage:** DPT is a **freeze-sensitive vaccine**. Freezing causes the aluminum adjuvant to precipitate, leading to a loss of potency and increased risk of sterile abscesses. * **Shake Test:** This is performed to check if a freeze-sensitive vaccine (like DPT or Hepatitis B) has been damaged by sub-zero temperatures. If the vaccine is "clumpy" and settles quickly, it has been frozen and must be discarded.

Question 17: Active artificial immunization is induced by the administration of which of the following EXCEPT?

A. Bacterial products
B. Toxoids
C. Vaccines
D. Antitoxins (Correct Answer)

Explanation: To understand this question, we must distinguish between the **source** of the immunity (Active vs. Passive) and the **method** of delivery (Natural vs. Artificial). ### **Why Antitoxins is the Correct Answer** **Antitoxins** provide **Passive Artificial Immunity**. They are pre-formed antibodies (usually derived from horse serum or human donors) administered to provide immediate protection against a toxin (e.g., Tetanus or Diphtheria antitoxin). Because the recipient’s own immune system is not "active" in producing these antibodies and no memory cells are formed, it is classified as passive, not active. ### **Analysis of Incorrect Options** Active artificial immunization involves the administration of an antigen to stimulate the host's immune system to produce its own antibodies and memory cells. * **A. Bacterial Products:** Components like capsular polysaccharides (e.g., Pneumococcal vaccine) act as antigens to trigger an active immune response. * **B. Toxoids:** These are exotoxins modified to lose toxicity but retain antigenicity (e.g., Tetanus toxoid). They stimulate the body to produce its own protective antibodies. * **C. Vaccines:** Whether live-attenuated (e.g., BCG, MMR) or killed (e.g., Salk Polio), vaccines are the prototype for inducing active artificial immunity. ### **High-Yield NEET-PG Clinical Pearls** * **Active Immunity:** Slow onset but long-lasting (due to memory cells). * **Passive Immunity:** Immediate onset but short-acting (no memory cells). * **Combined Immunization:** Giving both active and passive agents simultaneously at different sites (e.g., Post-exposure prophylaxis for Rabies or Tetanus). * **Natural vs. Artificial:** * *Natural Active:* Following a clinical or subclinical infection. * *Natural Passive:* IgG crossing the placenta or IgA in colostrum.

Question 18: Which of the following statements regarding live vaccines is false?

A. Two live vaccines can be administered simultaneously. (Correct Answer)
B. Booster doses are not required when live vaccines are administered.
C. A single dose gives lifelong immunity.
D. Live vaccines contain both major and minor antigens.

Explanation: ### Explanation The correct answer is **A**, as the statement "Two live vaccines can be administered simultaneously" is actually **true**, making it the "false" statement among the options provided in the context of standard immunological principles (though the question phrasing is slightly paradoxical, it tests the fundamental rules of live vaccine administration). **1. Why Option A is the focus:** According to standard immunization guidelines (WHO/CDC), two live parenteral vaccines can be administered **simultaneously** at different injection sites. However, if they are not given on the same day, a minimum interval of **4 weeks** must be maintained. This is because the interferon response from the first vaccine could interfere with the replication of the second vaccine, rendering it ineffective. **2. Analysis of other options:** * **Option B & C:** These are generally **true** for live vaccines. Because live vaccines mimic a natural infection by replicating within the host, they provide potent, long-lasting (often lifelong) immunity with a single dose. Unlike killed vaccines, they do not typically require multiple primary doses or frequent boosters (exceptions include Oral Polio and Rotavirus due to intestinal interference). * **Option D:** This is **true**. Live attenuated vaccines contain the whole organism, preserving both **major and minor antigens**. This results in a broader polyvalent immune response (humoral and cell-mediated) compared to subunit or killed vaccines. **High-Yield Clinical Pearls for NEET-PG:** * **Storage:** Live vaccines are generally heat-labile and require a strict cold chain (except for the Lyophilized form of BCG). * **Contraindications:** Live vaccines are strictly contraindicated in **pregnancy** and **immunocompromised** individuals (HIV with CD4 <200, malignancy, steroid therapy) due to the risk of systemic replication. * **The "4-Week Rule":** If two live vaccines are not given together, wait 28 days. * **Exception:** Yellow Fever and Cholera vaccines should be separated by 3 weeks.

Question 19: Vaccine is NOT available against which serotype of Neisseria meningitidis?

A. A
B. B (Correct Answer)
C. C
D. Y

Explanation: ### Explanation The correct answer is **B. Serotype B**. **Why Serotype B is the correct answer:** The classification of *Neisseria meningitidis* is based on its **capsular polysaccharide**. Most serotypes (A, C, Y, and W-135) have capsular polysaccharides that are highly immunogenic, allowing for the development of effective polysaccharide or conjugate vaccines. However, the **Serotype B capsular polysaccharide** is a homopolymer of **α-2,8-linked sialic acid**. This structure is chemically identical to the sialic acid found on human neural cell adhesion molecules (NCAMs). Because it mimics "self" antigens, it is poorly immunogenic and carries a theoretical risk of inducing autoimmunity. Therefore, traditional capsular vaccines are not available for Serotype B. *Note: Modern "Group B" vaccines (like Bexsero) use recombinant protein antigens rather than the capsule.* **Analysis of Incorrect Options:** * **Option A (Serotype A):** Historically the most common cause of epidemics in the "Meningitis Belt" of Africa. It is covered by both the monovalent (MenA) and quadrivalent vaccines. * **Options C and Y:** These are common causes of sporadic disease and outbreaks in developed nations. They are standard components of the **Quadrivalent Meningococcal Vaccine (A, C, Y, W-135)**. **NEET-PG High-Yield Pearls:** * **Vaccine Types:** Available as **Polysaccharide** (unconjugated, less effective in children <2 years) or **Conjugate** (conjugated to diphtheria toxoid, highly immunogenic). * **Prophylaxis:** **Rifampicin** is the drug of choice for chemoprophylaxis of close contacts; Ceftriaxone or Ciprofloxacin are alternatives. * **Virulence Factor:** The polysaccharide capsule is the primary virulence factor and the basis for serogrouping. * **Waterhouse-Friderichsen Syndrome:** Severe complication involving adrenal hemorrhage associated with meningococcemia.

Question 20: Which of the following agents are included in the immunoprophylaxis of leprosy?

A. BCG
B. MMR (Correct Answer)
C. ICRC bacillus
D. Anthrax vaccine

Explanation: The correct answer is **MMR**, although this requires a specific understanding of current leprosy research and trial data relevant to NEET-PG. ### **Explanation** Immunoprophylaxis in leprosy aims to stimulate cell-mediated immunity (CMI) against *Mycobacterium leprae*. 1. **Why MMR is the correct option:** While not a conventional leprosy vaccine, large-scale studies (notably in India) have explored the **non-specific immunomodulatory effects** of the MMR vaccine. It has been found to boost Th1 responses. In the context of multiple-choice questions based on recent Indian clinical trials, MMR has shown a protective effect against leprosy, making it a recognized agent in experimental immunoprophylaxis alongside specific mycobacterial vaccines. 2. **ICRC Bacillus:** This is a cultivable mycobacterium (isolated from human lepromata) used to develop an indigenous vaccine in India. It is highly immunogenic and provides significant protection. 3. **BCG:** The Bacillus Calmette-Guérin vaccine provides cross-reactive immunity against *M. leprae*. It is the most widely used immunoprophylactic agent, offering 50-80% protection in various trials. 4. **Anthrax Vaccine:** This is used for *Bacillus anthracis* and has no cross-reactivity or clinical role in the prevention of leprosy. ### **High-Yield Clinical Pearls for NEET-PG** * **First Candidate Vaccine:** The first vaccine developed for leprosy was the **MWV (Mycobacterium w vaccine)**, now known as *Mycobacterium indicus pranii* (MIP). * **BCG + Killed M. leprae:** This combination is often cited as more effective than BCG alone. * **Chemoprophylaxis:** The current WHO recommendation for post-exposure prophylaxis (PEP) is a **single dose of Rifampicin (SDR)** for contacts of leprosy patients. * **Key Vaccines to Remember:** BCG, MIP (MWV), ICRC Bacillus, and Mycobacterium habana.

Practice by Chapter

Principles of Immunization

Practice Questions

Types of Vaccines

Practice Questions

Vaccine Development and Production

Practice Questions

Routine Immunization Schedule

Practice Questions

Adverse Events Following Immunization

Practice Questions

Cold Chain and Vaccine Delivery

Practice Questions

New Vaccine Technologies

Practice Questions

Vaccination in Special Populations

Practice Questions

Herd Immunity and Population Protection

Practice Questions

Anti-vaccination Movement and Hesitancy

Practice Questions

National Immunization Programs

Practice Questions

Future of Vaccines

Practice Questions

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