Immunization and Vaccine-Preventable Diseases — MCQs

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

Question 91: Which of the following vaccines is contraindicated in pregnancy?

A. BCG
B. OPV
C. Yellow fever
D. Hepatitis B (Correct Answer)

Explanation: **Explanation:** The core principle in pregnancy immunization is that **Live Attenuated Vaccines** are generally contraindicated due to the theoretical risk of the vaccine virus crossing the placenta and infecting the fetus. Conversely, **Inactivated (Killed) vaccines** and **Recombinant vaccines** are considered safe. **Why Hepatitis B is the Correct Answer (Based on the provided key):** *Note: In standard clinical practice, Hepatitis B (a recombinant vaccine) is actually considered safe and indicated for high-risk pregnant women. However, if this specific question and key are from a source following older or specific examiner logic, it may be categorized as "avoidable" unless high risk is present. **Crucially, in most standard NEET-PG patterns, Live vaccines (BCG, OPV, Yellow Fever) are the ones strictly contraindicated.*** **Analysis of Options:** * **A. BCG (Live):** Strictly contraindicated. It is a live bacterial vaccine (Mycobacterium bovis) and poses a theoretical risk to the fetus. * **B. OPV (Live):** Generally avoided in pregnancy. While not as strictly contraindicated as BCG or MMR, IPV (Inactivated Polio Vaccine) is preferred if polio immunization is necessary. * **C. Yellow Fever (Live):** Contraindicated. It is only administered to pregnant women if they must travel to a high-endemic area where the risk of the disease outweighs the risk of the vaccine. * **D. Hepatitis B (Recombinant):** This is a non-live vaccine. It is safe and recommended for pregnant women at risk of infection (e.g., healthcare workers, partner of HBsAg+ individual). **High-Yield Clinical Pearls for NEET-PG:** 1. **Strictly Contraindicated in Pregnancy:** MMR (Measles, Mumps, Rubella), Varicella, BCG, and Yellow Fever. 2. **Safe/Recommended:** Tdap (Tetanus, Diphtheria, Pertussis) is routinely given (usually between 27-36 weeks). Inactivated Influenza is also highly recommended. 3. **The "Live Vaccine Rule":** Pregnancy should be avoided for **1 month** (28 days) after receiving a live vaccine (e.g., Rubella). 4. **Exception:** If a pregnant woman is bitten by a rabid animal, **Rabies vaccine** (Inactivated) and RIG are given immediately; life-saving prophylaxis is never withheld.

Question 92: Under the National Polio Eradication Programme, a case of Acute Flaccid Paralysis (AFP) is confirmed as Polio under which of the following circumstances, except?

A. If a case is lost to follow-up
B. If a case could not be confirmed because the patient died before confirmation
C. If a wild strain of poliovirus is isolated from the stool
D. If a patient develops paralysis 30 days after diagnosis of AFP (Correct Answer)

Explanation: ### Explanation In the context of the National Polio Eradication Programme (NPEP), the surveillance system is designed to be highly sensitive. To ensure no case is missed, the criteria for "confirming" a case of Polio include both virological and clinical parameters. **Why Option D is the Correct Answer (The Exception):** The definition of Acute Flaccid Paralysis (AFP) requires the **onset of paralysis to be acute and sudden**. If a patient develops paralysis 30 days *after* a diagnosis of AFP, it contradicts the definition of "acute" onset. Furthermore, for clinical confirmation of polio, the protocol requires the presence of **residual weakness at 60 days** after the initial onset, not the development of new paralysis a month later. **Analysis of Other Options:** * **Option C (Wild Poliovirus Isolation):** This is the "Gold Standard." Any AFP case where a wild poliovirus is isolated from stool samples is automatically confirmed as Polio. * **Options A & B (Clinical Confirmation):** Under the "Virological Classification Scheme," if stool samples are inadequate (or not collected), a case is confirmed as Polio based on clinical grounds if: 1. There is **residual weakness** at 60 days. 2. The patient is **lost to follow-up**. 3. The patient **dies** before the 60-day follow-up can be completed. **High-Yield Clinical Pearls for NEET-PG:** * **AFP Surveillance Age Group:** All children <15 years of age (and any person of any age if polio is suspected). * **Adequate Stool Samples:** Two samples collected 24–48 hours apart, within 14 days of the onset of paralysis. * **Non-Polio AFP Rate:** A key indicator of surveillance quality; it must be at least **2 per 100,000** children under 15 years. * **Stool Specimen Sensitivity:** Must be >80% for high-quality surveillance.

Question 93: Live vaccines are contraindicated in all of the following EXCEPT:

A. Breastfeeding (Correct Answer)
B. Pregnancy
C. HIV (asymptomatic)
D. Steroid-dependent immunosuppression

Explanation: **Explanation:** The core principle behind contraindications for live vaccines is the risk of uncontrolled viral or bacterial replication in a host with an altered immune system or a physiological state where fetal transmission is a concern. **1. Why Breastfeeding is the Correct Answer:** Breastfeeding is **not** a contraindication for live vaccines. Most live vaccines (e.g., MMR, Varicella) do not pass into breast milk, and even if they do, they do not cause disease in the infant. In fact, vaccinating a breastfeeding mother is often encouraged to protect the infant through "cocooning." The only rare exception is the Yellow Fever vaccine, which is avoided in breastfeeding mothers unless travel to an endemic area is unavoidable. **2. Analysis of Incorrect Options:** * **Pregnancy:** Live vaccines (especially MMR and Varicella) are contraindicated due to the theoretical risk of vertical transmission to the fetus, potentially causing congenital rubella syndrome or other teratogenic effects. * **HIV (Symptomatic/Immunosuppressed):** While asymptomatic HIV patients can receive some live vaccines (like MMR or BCG in specific protocols), live vaccines are generally contraindicated in those with severe immunosuppression (CD4 count <200 cells/mm³) due to the risk of disseminated vaccine-strain disease. * **Steroid-dependent Immunosuppression:** High-dose systemic corticosteroids (equivalent to ≥20 mg/day of prednisolone for >14 days) suppress the cell-mediated immune response, making live vaccines unsafe. **Clinical Pearls for NEET-PG:** * **Yellow Fever Vaccine:** Contraindicated in infants <6 months, pregnant women, and those with thymus disorders or egg allergy. * **Interval Rule:** Two live injectable vaccines must be given either on the same day or at least 4 weeks apart. * **HIV Exception:** BCG is contraindicated in all HIV-positive children (symptomatic or asymptomatic) according to WHO guidelines in high-prevalence areas.

Question 94: Measles vaccine given to a contact of a measles case exerts a protective effect within what timeframe?

A. 1 day
B. 3 days
C. 7 days (Correct Answer)
D. 10 days

Explanation: ### Explanation The correct answer is **7 days (Option C)**. **Medical Concept:** The effectiveness of post-exposure prophylaxis (PEP) for measles depends on the relationship between the **incubation period** of the disease and the **time taken for the vaccine to induce immunity**. * The incubation period of Measles is typically **10–14 days**. * The Measles vaccine (live attenuated) induces protective antibodies within **7 days** of administration. Because the vaccine-induced immunity develops faster (7 days) than the natural disease manifests (10+ days), administering the vaccine to a susceptible contact can prevent or significantly modify the severity of the disease, provided it is given within **72 hours (3 days)** of exposure. **Analysis of Options:** * **Option A (1 day):** This is too short for the body to mount an adaptive immune response (antibody production). * **Option B (3 days):** This is the **window period** during which the vaccine must be administered to be effective as PEP, but it is not the time it takes for the vaccine to provide protection. * **Option D (10 days):** By 10 days, the natural virus would have already completed its incubation period in the host, making the vaccine ineffective for post-exposure prevention. **High-Yield Clinical Pearls for NEET-PG:** 1. **Post-Exposure Prophylaxis (PEP):** Measles vaccine should be given within **72 hours** of exposure. 2. **Immunoglobulin (IG):** If more than 72 hours have passed but less than 6 days, Human Immunoglobulin (0.25 mL/kg) can be given to prevent/modify the disease. 3. **Vaccine Type:** Edmonston-Zagreb strain (live attenuated) is commonly used in India. 4. **Dose & Route:** 0.5 mL, Subcutaneous (Right upper arm). 5. **Reconstitution:** Must be used within **4 hours** of reconstitution; otherwise, discard (risk of Toxic Shock Syndrome due to *S. aureus* contamination).

Question 95: Vaccine-associated paralytic poliomyelitis is defined as those cases of acute flaccid paralysis who have residual weakness and from whose stool samples, vaccine-related poliovirus but no wild virus is isolated?

A. 6 months after the onset of paralysis
B. 60 days after the onset of paralysis (Correct Answer)
C. 6 days after the onset of paralysis
D. 60 days after the onset of paralysis and from whose stool samples, wild polio virus is isolated.

Explanation: ### Explanation **1. Understanding the Correct Answer (Option B)** Vaccine-associated paralytic poliomyelitis (VAPP) is a rare adverse event following the administration of the Oral Polio Vaccine (OPV), which contains live attenuated Sabin strains. In very rare instances, the attenuated virus reverts to neurovirulence. To clinically define VAPP, the following criteria must be met: * **Acute Flaccid Paralysis (AFP):** The patient must present with typical paralytic symptoms. * **Residual Weakness:** The paralysis must persist for **60 days** after the onset. This duration is the gold standard for distinguishing transient weakness from true paralytic polio. * **Laboratory Confirmation:** Stool samples must yield **vaccine-related poliovirus** while being negative for the wild poliovirus. **2. Analysis of Incorrect Options** * **Option A (6 months):** This is too long a duration for the standard surveillance definition of VAPP. * **Option C (6 days):** This is too short. Many non-polio AFP cases (like Guillain-Barré Syndrome) may show weakness at 6 days, but only polio typically leaves significant residual paralysis at the 60-day mark. * **Option D:** This is incorrect because the isolation of **wild poliovirus** would categorize the case as "Confirmed Wild Polio," not VAPP. VAPP specifically requires the isolation of the vaccine strain. **3. High-Yield Clinical Pearls for NEET-PG** * **VAPP vs. VDPV:** VAPP is a sporadic event in an individual vaccine recipient or contact. **VDPV (Vaccine-Derived Poliovirus)** refers to vaccine strains that have mutated and are circulating in a community with low immunization coverage. * **Risk Group:** VAPP is more common in **immunodeficient** children (especially those with B-cell deficiencies) and after the **first dose** of OPV. * **Prevention:** The shift from OPV to **IPV (Inactivated Polio Vaccine)** in the Universal Immunization Programme (UIP) is primarily aimed at eliminating the risk of VAPP and VDPV. * **Surveillance:** The "60-day follow-up" is a critical component of the Global Polio Eradication Initiative's AFP surveillance protocol.

Question 96: Mass immunization is indicated in the following conditions, except?

A. Leprosy (Correct Answer)
B. Cholera
C. Influenza
D. Tuberculosis

Explanation: **Explanation:** The concept of **Mass Immunization** refers to the rapid administration of a vaccine to a large proportion of a population to achieve herd immunity and interrupt disease transmission, typically during outbreaks or in endemic zones. **Why Leprosy is the correct answer:** Mass immunization is **not indicated** for Leprosy because there is currently no specific, highly effective vaccine available for mass scale use against *Mycobacterium leprae*. While the BCG vaccine offers some cross-protection against leprosy, it is primarily used for tuberculosis prevention. Leprosy control relies on **Early Diagnosis and Prompt Treatment (MDT)** and contact tracing rather than mass vaccination. **Analysis of Incorrect Options:** * **Cholera:** Mass vaccination with Oral Cholera Vaccines (OCV) is a WHO-recommended strategy in endemic areas and during humanitarian crises or outbreaks to prevent rapid spread. * **Influenza:** Mass immunization is frequently conducted, especially for high-risk groups and during pandemics (e.g., H1N1), to reduce morbidity and mortality. * **Tuberculosis:** BCG is administered as part of the Universal Immunization Programme (UIP) at birth. In high-burden countries like India, this constitutes a form of mass pediatric immunization to prevent severe forms like TB meningitis. **High-Yield Clinical Pearls for NEET-PG:** * **BCG Vaccine:** Provides varying protection (0-80%) against pulmonary TB but is highly effective against TB Meningitis and Miliary TB. It also offers ~50% protection against Leprosy. * **Herd Immunity:** Does not exist for Tetanus (as it is non-communicable) but is the goal of mass immunization for diseases like Polio and Measles. * **Ring Vaccination:** A strategy used in Smallpox (and recently Ebola) where only contacts and people in the immediate vicinity of a case are vaccinated, rather than the entire population.

Question 97: Which of the following vaccines is NOT included in Mission Indradhanush?

A. Diphtheria vaccine
B. Pertussis vaccine
C. Hepatitis B Vaccine
D. Meningococcal vaccine (Correct Answer)

Explanation: **Explanation:** **Mission Indradhanush (MI)** was launched by the Ministry of Health and Family Welfare in December 2014 to strengthen the Universal Immunization Programme (UIP) and achieve full immunization coverage for all children and pregnant women. **1. Why Meningococcal Vaccine is the Correct Answer:** The Meningococcal vaccine is **not** part of the National Immunization Schedule or Mission Indradhanush in India. It is primarily recommended for specific high-risk groups, travelers (e.g., Hajj pilgrims), or during documented outbreaks, but it is not administered as a routine childhood vaccine under the government’s flagship program. **2. Analysis of Incorrect Options:** Mission Indradhanush originally targeted **seven** vaccine-preventable diseases (hence the name "Indradhanush" or Rainbow): **Diphtheria, Pertussis, Tetanus, Polio, Measles, Childhood Tuberculosis, and Hepatitis B.** * **Options A & B (Diphtheria and Pertussis):** These are core components of the DPT/Pentavalent vaccine included since the inception of MI. * **C (Hepatitis B):** This is a key component of the Pentavalent vaccine administered at 6, 10, and 14 weeks, and is a primary target of MI. **3. High-Yield Clinical Pearls for NEET-PG:** * **Evolution of MI:** While it started with 7 vaccines, the program now covers protection against **12 diseases** nationally (including Rubella, Rotavirus, *Haemophilus influenzae* type B, and Polio) and **Japanese Encephalitis** (in endemic districts) and **Pneumococcal Conjugate Vaccine (PCV)**. * **Intensified Mission Indradhanush (IMI):** Launched to reach "left-outs" and "drop-outs" in low-coverage districts. The latest version is **IMI 5.0**, which focuses on improving Measles-Rubella (MR) elimination. * **Pentavalent Vaccine:** Protects against Diphtheria, Pertussis, Tetanus, Hepatitis B, and Hib. It replaced the DPT and Hep B standalone doses in the routine schedule.

Question 98: What is Sanchol?

A. Hormonal contraceptive
B. Cholera Vaccine (Correct Answer)
C. Nutritional supplement
D. Pesticide

Explanation: **Explanation:** **Shanchol** (often spelled Sanchol) is a bivalent, killed whole-cell **Oral Cholera Vaccine (OCV)**. It contains inactivated *Vibrio cholerae* O1 (Inaba and Ogawa serotypes) and O139. Unlike the earlier Dukoral vaccine, Shanchol does not contain the B-subunit of the cholera toxin, making it more heat-stable and cost-effective for mass immunization campaigns in endemic regions. **Analysis of Options:** * **Option B (Correct):** Shanchol is one of the two WHO-prequalified oral cholera vaccines (the other being Euvichol). It is administered in two doses, 14 days apart, and provides protection for up to 3–5 years. * **Option A (Incorrect):** Hormonal contraceptives include OCPs (Mala-N, Mala-D) or injectables (Antara/DMPA). Shanchol has no hormonal properties. * **Option C (Incorrect):** Nutritional supplements in public health usually refer to Iron-Folic Acid (IFA) or Vitamin A prophylaxis. * **Option D (Incorrect):** Pesticides used in community medicine include DDT, Malathion, or Temefos (Abate) for vector control. **High-Yield Clinical Pearls for NEET-PG:** * **Administration:** Shanchol is given **orally**. It does not require a buffer (unlike Dukoral), making it easier to administer in the field. * **Age Group:** It is licensed for use in individuals **≥1 year of age**. * **Herd Immunity:** It is highly effective in controlling outbreaks and is a key component of the "Ending Cholera: A Global Roadmap to 2030." * **Storage:** It should be stored at **2°C to 8°C**, but it is known for its relative stability at higher temperatures compared to other vaccines.

Question 99: Which of the following vaccines is NOT included in the Expanded Programme on Immunization (EPI) by WHO?

A. Tuberculosis
B. Pertussis
C. Chickenpox (Correct Answer)
D. Measles

Explanation: **Explanation:** The **Expanded Programme on Immunization (EPI)** was launched by the WHO in 1974 to reduce morbidity and mortality from vaccine-preventable diseases. The original EPI focused on six "killer diseases": Tuberculosis, Diphtheria, Pertussis, Tetanus, Polio, and Measles. **Why Chickenpox is the Correct Answer:** Chickenpox (Varicella) is **not** part of the standard WHO EPI or India’s Universal Immunization Programme (UIP). While the vaccine is available in the private sector, it is not included in the global public health mandate for routine immunization due to its relatively lower mortality rate compared to the original EPI diseases and cost-effectiveness considerations in developing nations. **Analysis of Incorrect Options:** * **A. Tuberculosis:** Included since the inception of EPI via the **BCG vaccine**, administered at birth. * **B. Pertussis:** Included as part of the **DPT (Triple Vaccine)** or Pentavalent vaccine, targeting *Bordetella pertussis*. * **D. Measles:** A core component of EPI since 1974. In India, it is currently administered as the **MR (Measles-Rubella)** vaccine. **High-Yield Facts for NEET-PG:** * **EPI in India:** Launched in 1978; renamed the **Universal Immunization Programme (UIP)** in 1985. * **Latest Additions to UIP:** Rotavirus vaccine, Pneumococcal Conjugate Vaccine (PCV), and Rubella. * **Mission Indradhanush:** Launched in 2014 to achieve 90% full immunization coverage. * **The "Six Killer Diseases":** Remember the mnemonic **"TDP-MPT"** (Tuberculosis, Diphtheria, Pertussis, Measles, Polio, Tetanus).

Question 100: Which statement is true regarding the SA-14-14-2 Japanese Encephalitis vaccine?

A. Cell culture derived live attenuated (Correct Answer)
B. Killed vaccine
C. Lifelong immunity
D. Primary schedule consists of 3 doses

Explanation: **Explanation:** The **SA-14-14-2 vaccine** is the most widely used vaccine for Japanese Encephalitis (JE) globally and is the specific strain used in India’s Universal Immunization Programme (UIP). **1. Why Option A is Correct:** The SA-14-14-2 is a **live attenuated vaccine** derived from **primary hamster kidney cell cultures**. It is highly immunogenic and has replaced the older mouse-brain derived inactivated vaccines due to its superior safety profile and ease of administration. **2. Why Other Options are Incorrect:** * **Option B (Killed vaccine):** While inactivated JE vaccines exist (e.g., JENVAC, which is Vero cell-derived), the SA-14-14-2 strain specifically refers to the live attenuated version. * **Option C (Lifelong immunity):** Unlike some live vaccines (like Yellow Fever), the JE vaccine does not provide lifelong immunity. Protective antibody levels tend to wane over time, necessitating booster doses or natural exposure in endemic areas to maintain immunity. * **Option D (Primary schedule):** Under the National Immunization Schedule (NIS) in India, the primary schedule consists of **2 doses** (administered at 9 months with Measles/MR and at 16–24 months with the DPT booster), not 3 doses. **High-Yield Clinical Pearls for NEET-PG:** * **Route:** Subcutaneous (0.5 ml). * **Storage:** Sensitive to heat and light; must be stored at +2°C to +8°C and reconstituted with the provided diluent (Phosphate Buffered Saline). * **Endemicity:** JE is the leading cause of viral encephalitis in Asia; in India, it is primarily prevalent in states like Uttar Pradesh, Bihar, and West Bengal. * **Contraindication:** As it is a live vaccine, it is contraindicated in pregnancy and immunocompromised individuals.

Practice by Chapter

Principles of Immunization

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Types of Vaccines

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Universal Immunization Program

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Cold Chain System

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Vaccine Storage and Handling

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Adverse Events Following Immunization

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National Immunization Schedule

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Polio Eradication

Practice Questions

Measles Elimination

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Tetanus Control

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New and Underutilized Vaccines

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Vaccination Coverage Assessment

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