Immunization and Vaccine-Preventable Diseases — MCQs

Immunization and Vaccine-Preventable Diseases Indian Medical PG Practice Questions and MCQs

Question 111: Ideally, immunization against poliomyelitis should be started at:

A. Birth (Correct Answer)
B. 6 weeks
C. 12 weeks
D. 9 months

Explanation: **Explanation:** The correct answer is **Birth** because, under the National Immunization Schedule (NIS) in India, the first dose of the Oral Polio Vaccine (OPV) is administered as a **"Zero Dose"** at birth. **Why Birth is Correct:** The primary objective of the birth dose is to induce local mucosal immunity in the gut before the infant is exposed to enteric pathogens. This "Zero Dose" improves the seroconversion rates of subsequent doses and ensures protection in areas where polio remains a threat or where wild poliovirus (WPV) circulation is a risk. It is ideally given within the first 15 days of life. **Analysis of Incorrect Options:** * **6 weeks:** This is when the **first primary dose** (OPV-1 and fIPV-1) is administered. While it is part of the primary series, it is not the "ideal" starting point if birth vaccination is possible. * **12 weeks:** This does not align with the standard schedule. The second primary dose is given at **10 weeks** (OPV-2). * **9 months:** This is the timing for the Measles-Rubella (MR) vaccine and the third dose of Fractional IPV (fIPV-3) in some states, but it is far too late to initiate polio immunization. **High-Yield Clinical Pearls for NEET-PG:** * **Pulse Polio Programme:** Uses only bivalent OPV (bOPV), which contains types 1 and 3. Type 2 was removed globally after the "Switch" in April 2016. * **fIPV (Fractional IPV):** Administered intradermally (0.1 ml) at 6, 14 weeks, and 9 months. * **VAPP vs. VDPV:** Vaccine-Associated Paralytic Polio (VAPP) occurs in the vaccine recipient; Vaccine-Derived Poliovirus (VDPV) is due to the environmental circulation of the mutated vaccine virus. * **India's Status:** India was declared Polio-free by the WHO on **March 27, 2014**.

Question 112: Gardasil protects against which of the following HPV strains?

A. 6
B. 16
C. 18
D. 33 (Correct Answer)

Explanation: **Explanation:** Human Papillomavirus (HPV) vaccines are classified based on the number of strains they cover. The question refers to the **Gardasil-9 (Nonavalent)** vaccine, which is the most comprehensive version currently available. **1. Why Option D (33) is Correct:** Gardasil-9 is designed to protect against **nine** strains of HPV: **6, 11, 16, 18, 31, 33, 45, 52, and 58**. Strains 31, 33, 45, 52, and 58 are high-risk types that contribute to approximately 15-20% of cervical cancers. Since strain 33 is included in the nonavalent formulation, it is the correct answer. **2. Analysis of Incorrect Options:** * **Options A, B, and C (6, 16, 18):** While Gardasil *does* protect against these strains, they are also covered by the older **Quadrivalent Gardasil** (6, 11, 16, 18). In the context of a multiple-choice question where only one answer is marked "correct" (33), the examiner is specifically testing your knowledge of the additional high-risk strains covered by the **Nonavalent** version (Gardasil-9). **3. High-Yield NEET-PG Clinical Pearls:** * **Types of HPV Vaccines:** * **Bivalent (Cervarix):** 16, 18 (Protects against 70% of cervical cancers). * **Quadrivalent (Gardasil):** 6, 11, 16, 18 (6 & 11 cause 90% of genital warts). * **Nonavalent (Gardasil-9):** 6, 11, 16, 18, 31, 33, 45, 52, 58. * **Cervavac:** India’s first indigenous quadrivalent HPV vaccine (6, 11, 16, 18). * **Dosage Schedule:** * <15 years: 2 doses (0, 6 months). * >15 years or immunocompromised: 3 doses (0, 1-2, 6 months). * **Target Age:** Ideally administered to girls (and boys) aged 9–14 years, before sexual debut.

Question 113: Which of the following is a vaccine-preventable cancer?

A. Hepatocellular carcinoma (Correct Answer)
B. Renal cell carcinoma
C. Lymphoma
D. Kaposi sarcoma

Explanation: **Explanation:** **1. Why Hepatocellular Carcinoma (HCC) is correct:** Hepatocellular carcinoma is primarily caused by chronic infection with **Hepatitis B Virus (HBV)** and Hepatitis C Virus (HCV). The **Hepatitis B vaccine** is a highly effective recombinant vaccine that prevents HBV infection, thereby preventing the subsequent development of chronic liver disease, cirrhosis, and HCC. It is often referred to as the first "anti-cancer vaccine." (Note: Human Papillomavirus (HPV) vaccine is the other major vaccine-preventable cancer tool, targeting Cervical Cancer). **2. Why the other options are incorrect:** * **B. Renal Cell Carcinoma:** The primary risk factors are smoking, obesity, hypertension, and genetic syndromes (like von Hippel-Lindau). There is no known infectious etiology or vaccine for RCC. * **C. Lymphoma:** While some lymphomas are associated with viruses (e.g., EBV and Burkitt lymphoma; HTLV-1 and Adult T-cell leukemia/lymphoma), there are currently no commercially available vaccines to prevent these specific malignancies. * **D. Kaposi Sarcoma:** This is caused by Human Herpesvirus 8 (HHV-8), typically in immunocompromised patients (HIV/AIDS). While antiretroviral therapy (ART) reduces incidence, no vaccine exists for HHV-8. **Clinical Pearls for NEET-PG:** * **HBV Schedule:** Under the Universal Immunization Programme (UIP), it is given at 0 (birth dose), 6, 10, and 14 weeks (as part of the Pentavalent vaccine). * **HPV Vaccine:** Recommended for girls aged 9–14 years to prevent **Cervical Cancer**. * **H. pylori:** While associated with Gastric MALT lymphoma and Adenocarcinoma, there is no vaccine; it is managed with triple/quadruple antibiotic therapy.

Question 114: Which of the following vaccines is NOT lyophilized (freeze-dried)?

A. BCG
B. OPV (Correct Answer)
C. Measles
D. JE Live vaccine

Explanation: **Explanation:** The core concept behind this question is the physical state of vaccines. **Lyophilization (freeze-drying)** is a process used to increase the shelf life and stability of certain vaccines, particularly live-virus vaccines, by removing water. **Why OPV is the correct answer:** Oral Polio Vaccine (OPV) is a **liquid vaccine** and is never lyophilized. It is highly heat-sensitive and must be stored at -20°C for long-term stability. Because it is already in a liquid state, it does not require a diluent before administration. **Why the other options are incorrect:** * **BCG:** This is a live bacterial vaccine that is always supplied in a **lyophilized** form. It must be reconstituted with Normal Saline (0.9% NaCl). * **Measles (and MR/MMR):** These are live viral vaccines that are highly unstable in liquid form at room temperature. They are **lyophilized** and must be reconstituted with Sterile Water for Injection. * **JE Live Vaccine (SA-14-14-2):** The live attenuated Japanese Encephalitis vaccine is **lyophilized** and requires reconstitution with the specific diluent provided by the manufacturer (usually Phosphate Buffered Saline). **High-Yield Clinical Pearls for NEET-PG:** 1. **Reconstitution Rule:** Once reconstituted, BCG, Measles, and JE vaccines must be used within **4 hours** or by the end of the session, whichever is earlier. Discard them after 4 hours to prevent toxic shock syndrome (especially with Measles/MR). 2. **Diluents:** Never switch diluents. BCG uses Normal Saline; Measles uses Sterile Water. 3. **Freeze-Sensitive Vaccines:** Remember the mnemonic **"DPT is frozen"** (DPT, DT, TT, Hep B, and Pentavalent). These are damaged by freezing and must never be stored in the freezer compartment. 4. **Heat-Sensitive:** OPV is the **most heat-sensitive** vaccine in the UIP.

Question 115: Which of the following statements regarding poliomyelitis is true?

A. Poliovirus is resistant to pasteurization.
B. For every clinical case, there may be 1000 subclinical cases in adults.
C. It commonly spreads by the fecal-oral route. (Correct Answer)
D. Most outbreaks of polio are due to type-3 poliovirus.

Explanation: ### Explanation **1. Why Option C is Correct:** Poliomyelitis is primarily an enteric infection. In areas with poor sanitation and hygiene (common in developing countries), the **fecal-oral route** is the most important mode of transmission. The virus multiplies in the Peyer's patches of the ileum and is excreted in the feces for several weeks. In the early stages of infection and in areas with high hygiene standards, droplet infection (respiratory route) can also occur, but the fecal-oral route remains the predominant epidemiological driver. **2. Why Other Options are Incorrect:** * **Option A:** Poliovirus is **heat-sensitive**. It is readily inactivated by **pasteurization** (62.5°C for 30 minutes), as well as by boiling and formaldehyde. * **Option B:** The ratio of clinical to subclinical cases varies by age. For every clinical case, there are roughly **1000 subclinical cases in children**, but only about **75 to 100 subclinical cases in adults**. Adults are more prone to developing paralytic disease if infected. * **Option D:** **Type 1 poliovirus** is the most common cause of paralytic poliomyelitis and is responsible for most outbreaks. Type 2 was the first to be eradicated globally (2015), followed by Type 3 (2019). **3. High-Yield Clinical Pearls for NEET-PG:** * **Reservoir:** Man is the only known reservoir (no animal carrier). * **Infectivity:** Most infectious during the late incubation period and the first week of clinical illness. * **Immunity:** Type-specific and lifelong. * **Vaccine:** **Salk (IPV)** induces humoral immunity (IgG); **Sabin (OPV)** induces both humoral and local intestinal immunity (IgA), preventing the spread of wild virus. * **VAPP vs VDPV:** Vaccine-Associated Paralytic Polio (VAPP) occurs in the vaccine recipient; Vaccine-Derived Poliovirus (VDPV) is due to the circulation of the mutated vaccine virus in the community.

Question 116: At what age is Vitamin A supplementation recommended?

A. 2 months
B. 9 months (Correct Answer)
C. 5-6 years
D. None of the above

Explanation: **Explanation:** **1. Why 9 Months is Correct:** Under the National Immunization Schedule (NIS) in India, Vitamin A supplementation begins at **9 completed months**, administered along with the **Measles/MR vaccine**. This timing is strategic because maternal antibodies against Measles begin to wane around this age, increasing the risk of infection. Measles is a major cause of Vitamin A depletion, which can lead to xerophthalmia and increased childhood mortality. The first dose is **1 lakh IU (1 ml)**, given orally. **2. Why Other Options are Incorrect:** * **A. 2 months:** At this age, infants are typically breastfed. Exclusive breastfeeding provides sufficient Vitamin A for the first six months of life. Supplementation is not indicated this early. * **C. 5-6 years:** While Vitamin A prophylaxis continues until age 5, it does not *start* here. The program includes a total of 9 doses: the first at 9 months, the second at 18 months (2 lakh IU), and subsequent doses every 6 months until the child reaches 5 years of age. **3. High-Yield Clinical Pearls for NEET-PG:** * **Total Doses:** A child receives a total of **9 doses** (17 lakh IU total) by age 5. * **Dosage:** 1st dose = 1 lakh IU; 2nd to 9th doses = 2 lakh IU each. * **Target Group:** The Vitamin A Prophylaxis Programme targets children aged 9–59 months. * **Therapeutic Dose:** If a child presents with active Xerophthalmia (e.g., Bitot’s spots), the treatment schedule is: **Day 0, Day 1, and Day 14** (2 lakh IU per dose for children >1 year). * **Public Health Impact:** Vitamin A supplementation can reduce all-cause child mortality by up to 23-24% in deficient areas.

Question 117: What is the recommended adult prophylaxis for meningococcal infection?

A. Rifampicin 600 mg twice daily for 2 days (Correct Answer)
B. Ampicillin 1 g daily for 5 days
C. Tetracycline 2 g daily for 1 day
D. Chloramphenicol 2 g daily for 2 days

Explanation: **Explanation:** The primary goal of prophylaxis in meningococcal infection is to eradicate the nasopharyngeal carriage of *Neisseria meningitidis*, thereby preventing secondary cases among close contacts. **Why Rifampicin is the Correct Choice:** Rifampicin is the drug of choice for chemoprophylaxis because it achieves high concentrations in salivary and respiratory secretions, effectively eliminating the carrier state. The standard adult regimen is **600 mg twice daily for 2 days** (total of 4 doses). For children, the dose is 10 mg/kg. **Analysis of Incorrect Options:** * **B, C, and D (Ampicillin, Tetracycline, Chloramphenicol):** While these antibiotics are effective in treating active clinical disease (meningitis or meningococcemia) because they cross the blood-brain barrier, they are **ineffective at eradicating the nasopharyngeal carrier state**. They do not reach sufficient concentrations in mucosal secretions to eliminate the bacteria from the throat. **High-Yield Clinical Pearls for NEET-PG:** * **Alternative Agents:** If Rifampicin is contraindicated (e.g., pregnancy), a single dose of **Ciprofloxacin (500 mg)** or a single IM injection of **Ceftriaxone (250 mg)** are recommended alternatives. * **Timing:** Prophylaxis should be administered as soon as possible, ideally within 24 hours of identifying the index case. It is generally not recommended if more than 14 days have passed. * **Target Group:** Prophylaxis is meant for "close contacts" (household members, daycare contacts, or healthcare workers exposed to respiratory secretions), not for casual contacts. * **Side Effect Note:** Warn patients that Rifampicin may turn urine and secretions orange.

Question 118: What does the sticker shown on a vaccine vial indicate?

A. Efficacy
B. Expiry
C. Viability
D. Cold chain maintenance (Correct Answer)

Explanation: ***Cold chain maintenance*** - The sticker is a **Vaccine Vial Monitor (VVM)** that uses heat-sensitive color changes to indicate if the vaccine has been exposed to excessive heat during storage or transport. - It provides a **cumulative heat exposure record** showing whether the **cold chain** has been maintained throughout the vaccine's journey from manufacturer to administration. *Efficacy* - Efficacy refers to how well a vaccine works in **controlled clinical trials** and is not indicated by any sticker on the vial. - This information is determined through **clinical studies** and documented in product literature, not visual indicators. *Expiry* - The **expiration date** is printed directly on the vaccine vial label as text, not indicated by a color-changing sticker. - VVM stickers complement but do not replace **expiry date information** which shows when the vaccine should no longer be used. *Viability* - Viability refers to whether vaccine components are **biologically active** and cannot be determined by external visual indicators alone. - This requires **laboratory testing** and sterility assessments that are not reflected in sticker technology.

Question 119: Which of the following vaccines is contraindicated in children with egg allergy?

A. Yellow fever (Correct Answer)
B. MMR
C. TT
D. OPV

Explanation: **Explanation:** The correct answer is **Yellow Fever**. **1. Why Yellow Fever is the correct answer:** The Yellow Fever vaccine (17D strain) is cultured in **embryonated chicken eggs**. During the manufacturing process, residual egg proteins (ovalbumin) remain in the final vaccine product. In individuals with a severe egg allergy (anaphylaxis), these proteins can trigger a life-threatening hypersensitivity reaction. Therefore, severe egg allergy is a formal contraindication for the Yellow Fever vaccine. **2. Analysis of Incorrect Options:** * **MMR (Measles, Mumps, Rubella):** While the measles and mumps components are grown in chick embryo fibroblast cultures, they do not contain significant amounts of egg albumin. Current guidelines (CDC/WHO) state that MMR can be safely administered to children with egg allergies in a routine primary care setting. * **TT (Tetanus Toxoid):** This is a toxoid vaccine produced from the toxin of *Clostridium tetani*. It involves no egg-based media in its production. * **OPV (Oral Polio Vaccine):** This is a live attenuated vaccine grown in monkey kidney cell cultures (Vero cells) or human diploid cells, not eggs. **3. NEET-PG High-Yield Pearls:** * **Egg-containing vaccines:** Yellow Fever and Influenza (most types) are the primary concerns. * **Rabies Vaccine:** The Cell Culture Rabies Vaccine (CCRV) is safe, but the older **Purified Chick Embryo Cell (PCEC)** vaccine should be used with caution in severe egg allergy. * **Yellow Fever Vaccine Facts:** It is a live attenuated vaccine; immunity starts after 10 days and lasts for life (International Health Regulations); it is contraindicated in infants <6 months and immunocompromised individuals.

Question 120: The first BCG vaccine is prepared from which organism?

A. Mycobacterium tuberculosis
B. Mycobacterium bovis (Correct Answer)
C. Mycobacterium kansasii
D. Mycobacterium scrofulaceum

Explanation: **Explanation:** **Correct Answer: B. Mycobacterium bovis** The BCG (Bacillus Calmette-Guérin) vaccine is a live attenuated vaccine derived from a strain of **Mycobacterium bovis**. It was developed by Albert Calmette and Camille Guérin at the Pasteur Institute by serially subculturing the bovine strain 230 times over 13 years (1908–1921). This process reduced the virulence of the bacteria while maintaining its immunogenicity, allowing it to provide cross-protection against human tuberculosis. **Analysis of Incorrect Options:** * **A. Mycobacterium tuberculosis:** This is the primary causative agent of human tuberculosis. While it is the target of the vaccine, the vaccine itself is not derived from this human strain to avoid the risk of causing active disease in the recipient. * **C. Mycobacterium kansasii:** This is a "Photochromogen" (Runyon Group I) non-tuberculous mycobacterium (NTM) that causes chronic pulmonary disease similar to TB. It is not used in vaccine production. * **D. Mycobacterium scrofulaceum:** This is a "Scotochromogen" (Runyon Group II) NTM, commonly associated with cervical lymphadenitis in children. It is not used for BCG production. **High-Yield Clinical Pearls for NEET-PG:** * **Strain used in India:** The **Danish 1331** strain is currently used for vaccine production. * **Administration:** Given **Intradermally** (0.05 ml for neonates <1 month; 0.1 ml for infants >1 month) using an **Omega/Tuberculin syringe**. * **Site:** Left upper arm (deltoid region) to maintain uniformity for scar inspection. * **Reconstitution:** Must be reconstituted with **Normal Saline** (Distilled water is irritant; Dextrose can lead to contamination). * **Evolution of the BCG site:** Papule (2-3 weeks) → Glazed ulcer (5-6 weeks) → Permanent **pitted scar** (6-12 weeks). * **Protective Effect:** Highly effective against **Tubercular Meningitis** and **Miliary TB** in children, but has variable efficacy against adult pulmonary TB.

Practice by Chapter

Principles of Immunization

Practice Questions

Types of Vaccines

Practice Questions

Universal Immunization Program

Practice Questions

Cold Chain System

Practice Questions

Vaccine Storage and Handling

Practice Questions

Adverse Events Following Immunization

Practice Questions

National Immunization Schedule

Practice Questions

Polio Eradication

Practice Questions

Measles Elimination

Practice Questions

Tetanus Control

Practice Questions

New and Underutilized Vaccines

Practice Questions

Vaccination Coverage Assessment

Practice Questions

Want unlimited practice?

Get full access to all questions, explanations, and performance tracking.

Start For Free