Vaccine and Vaccination — MCQs

Vaccine and Vaccination Indian Medical PG Practice Questions and MCQs

Question 61: A synthetic “cocktail” vaccine SPf66 has shown potential for protection against which of the following?

A. Dengue/ DHF
B. Japanese encephalitis
C. Lymphatic filariasis
D. Falciparum Malaria (Correct Answer)

Explanation: **Explanation:** The correct answer is **Falciparum Malaria**. **SPf66** is a historically significant synthetic peptide "cocktail" vaccine developed by Manuel Elkin Patarroyo in the 1980s. It is a chimeric protein consisting of peptides from the asexual blood stages (merozoites) and the sporozoite stage of *Plasmodium falciparum*. It was the first malaria vaccine to undergo large-scale field trials; however, while initial results in South America were promising, subsequent trials in Africa and Southeast Asia showed low or inconsistent efficacy, leading to its replacement by more modern candidates like **RTS,S/AS01 (Mosquirix)** and **R21/Matrix-M**. **Why other options are incorrect:** * **Dengue/DHF:** The primary vaccine for Dengue is **Dengvaxia (CYD-TDV)**, a live-attenuated tetravalent vaccine. * **Japanese Encephalitis (JE):** Common vaccines for JE include **SA 14-14-2** (live-attenuated), **JENVAC** (inactivated), and **Ixiaro**. * **Lymphatic Filariasis:** There is currently no licensed vaccine for Filariasis; control relies on Mass Drug Administration (MDA) using Diethylcarbamazine (DEC) and Albendazole. **High-Yield Clinical Pearls for NEET-PG:** * **RTS,S/AS01 (Mosquirix):** The first WHO-recommended malaria vaccine. It targets the **circumsporozoite protein (CSP)** of *P. falciparum*. * **R21/Matrix-M:** The second malaria vaccine recently recommended by the WHO, noted for high efficacy and easier manufacturing. * **SPf66** is often tested as a "historical first" or "synthetic peptide" vaccine keyword in competitive exams. * **Malaria Vaccine Target:** Most current vaccines target the **pre-erythrocytic stage** to prevent the parasite from infecting the liver.

Question 62: Which of the following vaccines is administered subcutaneously?

A. BCG
B. Live influenza
C. Measles (Correct Answer)
D. Typhoid

Explanation: **Explanation:** The route of administration for vaccines is determined by the immunogenicity and the risk of local adverse reactions. The **Measles vaccine** (and the combined MMR vaccine) is classically administered via the **Subcutaneous (SC)** route, typically over the right upper arm. **Analysis of Options:** * **A. BCG:** Administered **Intradermally (ID)** using a tuberculin syringe. This route is essential to induce a delayed-type hypersensitivity reaction and to minimize the risk of deeper tissue abscesses. * **B. Live Influenza:** The live attenuated influenza vaccine (LAIV) is administered **Intranasally** via a spray, mimicking the natural route of viral entry to induce mucosal immunity. * **C. Measles (Correct):** It is a live attenuated vaccine that requires subcutaneous injection to ensure slow absorption and optimal processing by dendritic cells in the fatty tissue. * **D. Typhoid:** The injectable Typhoid vaccine (Vi polysaccharide) is given **Intramuscularly (IM)** or deep subcutaneous, while the Ty21a strain is an **Oral** vaccine. **High-Yield Clinical Pearls for NEET-PG:** * **Subcutaneous Vaccines (Mnemonic: "MR. J"):** **M**easles/MMR, **R**ubella, **J**apanese Encephalitis (SA-14-14-2 strain), and Yellow Fever. * **Intradermal Vaccines:** BCG, Rabies (IDRV regimen), and Fractional IPV (fIPV). * **Intramuscular Vaccines:** Most killed/subunit vaccines like DPT, Hepatitis B, Tetanus, and Pentavalent. * **Site of Injection:** For infants, the anterolateral aspect of the thigh is preferred for IM injections; for adults, the deltoid muscle is used.

Question 63: What vaccines are recommended for patients undergoing splenectomy, excluding one option?

A. Haemophilus influenzae type b
B. Meningococcal vaccine
C. Pneumococcal vaccine
D. Typhoid vaccine (Correct Answer)

Explanation: ### Explanation The spleen plays a critical role in the immune system by filtering blood and housing macrophages and B-cells. It is the primary site for the production of antibodies against **encapsulated organisms**. Patients undergoing splenectomy (asplenia) are at a significantly high risk for **Overwhelming Post-Splenectomy Infection (OPSI)**, a life-threatening sepsis caused primarily by encapsulated bacteria. **Why Typhoid Vaccine is the Correct Answer:** While *Salmonella typhi* is a Gram-negative rod, it is not typically categorized among the "big three" encapsulated organisms that cause rapid-onset OPSI. Routine vaccination for Typhoid is not a standard pre-splenectomy protocol unless the patient is traveling to an endemic area. Therefore, it is the "except" option. **Why the Other Options are Incorrect:** * **Pneumococcal vaccine (C):** *Streptococcus pneumoniae* is the most common cause of OPSI (responsible for ~50-90% of cases). Both PCV13 and PPSV23 are mandatory. * **Haemophilus influenzae type b (A):** Hib is a major encapsulated pathogen that can cause severe pneumonia and meningitis in asplenic individuals. * **Meningococcal vaccine (B):** *Neisseria meningitidis* is the third essential encapsulated organism requiring vaccination (MenACWY and MenB). **High-Yield Clinical Pearls for NEET-PG:** * **Timing:** Ideally, vaccines should be administered **2 weeks before** an elective splenectomy. If the surgery is an emergency, vaccinate **2 weeks after** the procedure to ensure an adequate immune response. * **The "Big Three":** Always remember the triad for asplenia: **Pneumococcus, Meningococcus, and Hib.** * **Annual Prophylaxis:** These patients should also receive the **Annual Influenza vaccine**, as viral infections can predispose them to secondary bacterial infections. * **Peripheral Smear:** Look for **Howell-Jolly bodies** (nuclear remnants) and **Pappenheimer bodies**, which are classic post-splenectomy findings.

Question 64: Which of the following is not a killed vaccine?

A. Polio
B. HBV
C. HAV
D. Yellow fever vaccine (Correct Answer)

Explanation: **Explanation:** The correct answer is **Yellow fever vaccine** because it is a **Live Attenuated Vaccine**, whereas the other options represent killed or subunit vaccines. **1. Why Yellow Fever is the correct answer:** The Yellow fever vaccine (specifically the **17D strain**) is a classic example of a live attenuated viral vaccine. It provides long-lasting immunity (often lifelong) with a single dose. In the context of NEET-PG, it is crucial to remember that live vaccines are contraindicated in pregnancy and immunocompromised individuals. **2. Analysis of Incorrect Options:** * **Polio:** While Polio has two vaccine types, the **Salk vaccine (IPV)** is a **Killed (Inactivated)** vaccine. Since the question asks which is *not* a killed vaccine, and IPV is a standard killed vaccine, this option is excluded. (Note: Sabin/OPV is live). * **HBV (Hepatitis B):** This is a **Recombinant Subunit vaccine** (using HBsAg produced in yeast). In microbiology classifications, subunit/fractional vaccines are categorized under the "non-live" or "killed" umbrella as they do not contain live replicating organisms. * **HAV (Hepatitis A):** The most commonly used Hepatitis A vaccines (e.g., Havrix) are **Killed/Inactivated** viral vaccines. **Clinical Pearls for NEET-PG:** * **Mnemonic for Live Vaccines:** "**Rome Is My Best Place**" (**R**ubella, **O**PV, **M**easles/Mumps, **E**ndemic Typhus, **I**nfluenza (Intranasal), **S**abin/Smallpox, **M**TC/MMR, **B**CG, **P**olio/Yellow **P**ever). * **Yellow Fever Specifics:** It is a mandatory vaccine for international travel to endemic zones (Africa/South America). Immunity starts after 10 days and the certificate is valid for life. * **Killed Vaccines Mnemonic:** "**K**illed **P**olice **A**re **I**n **T**hailand" (**K**olmer/Killed, **P**ertussis/Polio (Salk), **A**BV/HAV, **I**nfluenza (Injectable), **T**yphoid (TAB)).

Question 65: Neomycin is used in which of the following vaccines to prevent bacterial contamination?

A. OPV and BCG
B. MMR and IPV (Correct Answer)
C. DPT and HPV
D. Hib and HPV

Explanation: **Explanation:** The correct answer is **B. MMR and IPV**. **1. Underlying Medical Concept:** During the manufacturing of viral vaccines (like MMR and IPV), the viruses are grown in cell cultures or chick embryos. These growth media are highly susceptible to bacterial contamination. To ensure sterility without interfering with viral replication, trace amounts of antibiotics are added. **Neomycin** is the most commonly used aminoglycoside for this purpose. It is specifically used in the **MMR** (Measles, Mumps, Rubella), **IPV** (Inactivated Poliovirus Vaccine), and **Varicella** vaccines. **2. Analysis of Options:** * **Option A (OPV and BCG):** While OPV contains neomycin and streptomycin, **BCG** is a live attenuated bacterial vaccine (M. bovis). Adding antibiotics like neomycin would kill the vaccine strain itself, rendering it ineffective. * **Option C & D (DPT, HPV, Hib):** **DPT** (Toxoids/Killed bacteria) and **Hib** (Polysaccharide conjugate) are bacterial subunit vaccines that do not require cell culture growth, thus neomycin is not a standard additive. **HPV** is a recombinant VLP (Virus-Like Particle) vaccine produced in yeast or insect cells and typically does not contain neomycin. **3. High-Yield Clinical Pearls for NEET-PG:** * **Hypersensitivity:** The presence of neomycin is clinically significant because it is a contraindication for patients with a known **anaphylactic allergy to neomycin**. * **Thiomersal:** A mercury-based preservative used in multi-dose vials (e.g., DPT, Hepatitis B) to prevent fungal/bacterial growth, but it is **absent** in single-dose live vaccines like MMR. * **Other Additives:** Gelatin is often used as a stabilizer in MMR; it is the most common cause of vaccine-associated anaphylaxis.

Question 66: All are live vaccines except?

A. BCG
B. Polio
C. Rabies (Correct Answer)
D. Measles

Explanation: **Explanation:** The correct answer is **Rabies** because it is a **killed (inactivated) vaccine**. In medical microbiology, vaccines are classified based on the state of the antigen. Live attenuated vaccines use pathogens that are weakened but still capable of replicating within the host to induce immunity, whereas killed vaccines use pathogens that have been destroyed (usually by heat or chemicals like formaldehyde) and cannot replicate. **Analysis of Options:** * **Rabies (Correct):** The modern Rabies vaccines (like Purified Chick Embryo Cell Vaccine - PCECV or Human Diploid Cell Vaccine - HDCV) are inactivated vaccines. They require multiple doses and boosters because they do not replicate in the body. * **BCG (Incorrect):** This is a live attenuated bacterial vaccine derived from *Mycobacterium bovis*. It is a classic example of a live vaccine given at birth. * **Polio (Incorrect):** While Polio has two forms, the question refers to the general category. The **Oral Polio Vaccine (Sabin)** is a live attenuated vaccine. (Note: The Injectable Polio Vaccine/Salk is killed). * **Measles (Incorrect):** Measles is a highly immunogenic live attenuated viral vaccine, usually administered as part of the MMR or MR combination. **High-Yield Clinical Pearls for NEET-PG:** * **Mnemonic for Live Vaccines:** "**B**oy **R**omeo **G**ive **M**y **L**ove **S**picy **T**ypy **V**ery **Y**ellow" (**B**CG, **R**ubella/Rotavirus, **G**umprecht/OPV, **M**easles/Mumps, **L**ive Influenza, **S**mallpox, **T**yphoid (Ty21a), **V**aricella, **Y**ellow Fever). * **Contraindication:** Live vaccines are generally contraindicated in **pregnancy** and **immunocompromised** individuals (except HIV patients before the symptomatic stage). * **Storage:** Most live vaccines are heat-sensitive and must be stored in the freezer or the coldest part of the cold chain.

Question 67: Human immunoglobulin is given in all except?

A. Measles (Correct Answer)
B. Hepatitis B
C. Rabies
D. Chickenpox

Explanation: **Explanation:** The question asks for the condition where **Human Immunoglobulin (Ig)** is generally *not* the standard post-exposure prophylaxis or treatment compared to the other options. **1. Why Measles is the Correct Answer:** While immunoglobulin can be used for measles post-exposure prophylaxis in specific high-risk individuals (e.g., immunocompromised or infants), the standard of care for the general population is the **Live Attenuated Vaccine**. More importantly, in the context of competitive exams, Measles is often the "except" choice because the **Normal Human Immunoglobulin (NHIG)** is used, whereas Hepatitis B, Rabies, and Varicella require **Specific (Hyperimmune) Immunoglobulins**. **2. Analysis of Incorrect Options:** * **Hepatitis B:** **HBIG (Hepatitis B Immunoglobulin)** is a standard protocol for post-exposure prophylaxis (e.g., needle-stick injuries in non-immune individuals) and for neonates born to HBsAg-positive mothers. * **Rabies:** **HRIG (Human Rabies Immunoglobulin)** is mandatory for Category III bites to provide immediate passive immunity at the wound site before the vaccine-induced active immunity kicks in. * **Chickenpox:** **VZIG (Varicella-Zoster Immunoglobulin)** is indicated for post-exposure prophylaxis in high-risk groups (pregnant women, neonates, and immunocompromised patients) exposed to Varicella. **Clinical Pearls for NEET-PG:** * **Passive Immunity:** Provides immediate but temporary protection. * **Specific vs. Normal Ig:** HBIG, HRIG, VZIG, and Tetanus (TIG) are **Hyperimmune Igs** (high antibody titers). Measles and Hepatitis A typically utilize **Normal Human Ig**. * **Live Vaccine Rule:** If a patient receives Immunoglobulin, live vaccines (like MMR or Varicella) should generally be delayed for **3 to 11 months** (depending on the dose) to prevent interference with the immune response.

Question 68: All of the following are true about the Salk vaccine except:

A. It prevents paralysis.
B. Oral polio vaccine can be given as a booster.
C. It is contraindicated in immunocompromised patients. (Correct Answer)
D. It is easily transported.

Explanation: The Salk vaccine is the **Inactivated Polio Vaccine (IPV)**, which consists of killed virus particles. Understanding its properties is crucial for distinguishing it from the Sabin (Oral Polio Vaccine/OPV). ### Why Option C is the Correct Answer (The False Statement) The Salk vaccine (IPV) is an **inactivated (killed) vaccine**. Unlike live-attenuated vaccines (like OPV, BCG, or MMR), killed vaccines cannot replicate in the host and therefore cannot cause disease. Consequently, IPV is **not contraindicated** in immunocompromised patients; in fact, it is the preferred choice for HIV-positive individuals or those with primary immunodeficiencies to avoid the risk of Vaccine-Associated Paralytic Polio (VAPP). ### Analysis of Other Options * **A. It prevents paralysis:** IPV induces strong systemic immunity (IgG), which prevents the virus from spreading to the Central Nervous System (CNS), thereby preventing viremia and subsequent paralysis. * **B. OPV can be given as a booster:** In many immunization schedules (including India’s current strategy), IPV is used to provide systemic protection, while OPV is used as a booster to enhance mucosal immunity (IgA) and provide herd protection. * **D. It is easily transported:** Since it is a killed vaccine, IPV is more heat-stable than the live-attenuated OPV. It does not require the stringent "ultra-cold chain" management that OPV does, making it easier to transport without losing potency. ### High-Yield NEET-PG Pearls * **Immunity:** IPV provides **Humoral immunity (IgG)**; OPV provides both **Humoral (IgG) and Intestinal (IgA)** immunity. * **VAPP & VDPV:** These risks are associated **only with OPV**, never with IPV. * **Current Schedule (India):** Fractional dose IPV (fIPV) is given intradermally at 6, 14 weeks, and 9 months. * **Salk vs. Sabin:** Remember **"Salk = Killed"** (both have the letter 'K').

Question 69: The strain used for the commercial production of the BCG vaccine is:

A. Danish-1331 (Correct Answer)
B. Tween-80
C. Bacille Calmette Guerin
D. PPD-RT-23

Explanation: **Explanation:** The **BCG (Bacille Calmette-Guérin)** vaccine is a live attenuated vaccine derived from *Mycobacterium bovis*. For standardized global production, specific seed lots are used. **1. Why Danish-1331 is Correct:** The **Danish-1331 (Copenhagen)** strain is the most widely used strain for the commercial production of the BCG vaccine globally. It is favored because it provides a consistent and potent immune response. In India, the BCG vaccine is manufactured at the BCG Vaccine Laboratory in Guindy, Chennai, specifically using this Danish-1331 strain. **2. Analysis of Incorrect Options:** * **Tween-80:** This is not a strain but a **detergent/surfactant** added to the liquid medium (like Dubos medium) to prevent the clumping of Mycobacteria, allowing them to grow as a smooth, homogenous suspension. * **Bacille Calmette Guerin:** This is the name of the vaccine itself, named after Albert Calmette and Camille Guérin who attenuated the original *M. bovis* strain over 230 passages. It is not the specific commercial sub-strain. * **PPD-RT-23:** This refers to **Purified Protein Derivative (RT-23 with Tween-80)**, which is the standard antigen used for performing the **Mantoux Test** (Tuberculin Skin Test), not for vaccine production. **3. High-Yield Clinical Pearls for NEET-PG:** * **Type of Vaccine:** Live attenuated (derived from *M. bovis*). * **Site & Route:** Left upper arm (deltoid), **Intradermal** (using an Omega/Tuberculin syringe). * **Dose:** 0.1 ml (0.05 ml for neonates below 4 weeks). * **Diluent:** Normal Saline (Distilled water causes irritation; Dextrose causes death of bacilli). * **The BCG Scar:** It is the only vaccine that leaves a permanent scar, typically forming 6–12 weeks after vaccination. * **Protective Effect:** Highly effective against TB meningitis and miliary TB in children, but has variable efficacy against adult pulmonary TB.

Question 70: Which one of the following is a conjugated vaccine?

A. Hepatitis B
B. Rubella
C. Haemophilus influenza (Correct Answer)
D. Pertussis

Explanation: **Explanation:** The correct answer is **Haemophilus influenzae type b (Hib)**. **1. Why Hib is a Conjugated Vaccine:** The primary virulence factor of *H. influenzae* is its polysaccharide capsule (Polyribosylribitol phosphate - PRP). Polysaccharides are **T-cell independent antigens**, which are poorly immunogenic in children under 2 years of age because their immune systems cannot mount a robust response without T-cell help. To overcome this, the polysaccharide is **conjugated** (chemically linked) to a carrier protein (e.g., Tetanus toxoid or Diphtheria CRM197). This converts the immune response to **T-cell dependent**, leading to the production of high-affinity IgG antibodies and long-term immunological memory. **2. Analysis of Incorrect Options:** * **Hepatitis B:** This is a **Recombinant DNA vaccine** (Subunit vaccine) produced by inserting the HBsAg gene into yeast cells (*Saccharomyces cerevisiae*). * **Rubella:** This is a **Live Attenuated vaccine** (RA 27/3 strain), usually administered as part of the MMR or MR vaccine. * **Pertussis:** The modern version (aP) is an **Acellular vaccine** containing purified components (toxoid, filamentous hemagglutinin), while the older version (wP) is a **Killed/Inactivated vaccine**. **3. NEET-PG High-Yield Pearls:** * **Common Conjugated Vaccines:** Remember the mnemonic **"SPH"** – *Streptococcus pneumoniae* (PCV), *Polysaccharide* (Hib), and *Haemophilus* (Hib), plus Meningococcal vaccine. * **Advantage:** Conjugation induces **mucosal immunity** (IgA), which reduces nasopharyngeal carriage, leading to **herd immunity**. * **Age Factor:** Pure polysaccharide vaccines (like PPV23) are ineffective in infants; conjugated vaccines are the standard for the pediatric immunization schedule.

Practice by Chapter

Principles of Immunization

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Types of Vaccines

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Vaccine Development and Production

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Routine Immunization Schedule

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Adverse Events Following Immunization

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Cold Chain and Vaccine Delivery

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New Vaccine Technologies

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Vaccination in Special Populations

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Herd Immunity and Population Protection

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Anti-vaccination Movement and Hesitancy

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National Immunization Programs

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Future of Vaccines

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