Immunization and Vaccine-Preventable Diseases — MCQs

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

Question 101: For survey of immunization, what is the WHO age group selected?

A. 12 - 23 months (Correct Answer)
B. 0 - 6 months
C. 6 - 12 months
D. 2 - 5 years

Explanation: ### Explanation **1. Why the Correct Answer is Right (12–23 Months):** The WHO recommends the **12–23 months** age group for immunization coverage surveys (specifically the "30-cluster survey" methodology) because it represents the most recent cohort of children who should have completed their primary immunization schedule. * **Medical Concept:** By 12 months, a child is expected to have received all basic vaccines (BCG, 3 doses of DPT/Pentavalent, OPV, and Measles/MR). Surveying this group allows health officials to assess the **success of the previous year's immunization program** and identify "drop-outs" or missed opportunities before the child moves further into early childhood. **2. Why the Incorrect Options are Wrong:** * **0–6 months (Option B):** At this age, the child is still in the middle of the primary series (e.g., Pentavalent 2 or 3). Surveying them would not give an accurate picture of "fully immunized" status. * **6–12 months (Option C):** While closer to completion, many children in developing regions receive their first dose of Measles/MR at 9 months. Surveying this group would prematurely label children as "partially immunized" before they have had the full window to complete the schedule. * **2–5 years (Option D):** This group is too old for a primary coverage survey. Recall bias from parents increases with time, making the data less reliable for evaluating current program performance. **3. High-Yield Clinical Pearls for NEET-PG:** * **30-Cluster Survey:** Developed by WHO; involves selecting 30 clusters and 7 children in each cluster (Total = 210 children). * **Fully Immunized Child:** A child who has received BCG, 3 doses of OPV, 3 doses of DPT (or Pentavalent), and 1 dose of Measles vaccine before the first birthday. * **Primary Objective:** The survey is designed to estimate immunization coverage within a 5%–10% margin of error. * **Denominator:** For calculating immunization coverage in a community, the denominator is the "Total number of infants (0-1 year)" or "Total live births."

Question 102: Which of the following groups can receive a live attenuated vaccine?

A. Children under 8 years (Correct Answer)
B. HIV patients
C. Patients on steroids
D. Patients on radiation

Explanation: **Explanation:** The core concept tested here is the **contraindication of live attenuated vaccines in immunocompromised states.** Live vaccines (e.g., BCG, OPV, Measles, MMR) contain weakened pathogens that can replicate. In a healthy individual, the immune system controls this replication to create immunity; however, in immunocompromised individuals, the vaccine strain can cause disseminated, life-threatening disease. **1. Why Option A is Correct:** Children under 8 years of age (who are otherwise healthy) have functional immune systems. In fact, the National Immunization Schedule (NIS) focuses heavily on this age group for live vaccines like BCG (at birth), OPV/Rotavirus (infancy), and Measles/MRR (9 months and 16-24 months). Age itself is not a contraindication unless the child has an underlying primary immunodeficiency. **2. Why Options B, C, and D are Incorrect:** * **B. HIV Patients:** Generally, live vaccines are contraindicated in symptomatic HIV or those with severe immunosuppression (CD4 count <200 cells/mm³). While asymptomatic HIV patients may receive some live vaccines (like Measles), as a general rule for exams, HIV is a contraindication for live vaccines (especially BCG and Yellow Fever). * **C. Patients on Steroids:** High-dose systemic corticosteroids (equivalent to ≥20 mg/day of Prednisone for >2 weeks) suppress T-cell function, making live vaccines unsafe. * **D. Patients on Radiation:** Radiotherapy depletes rapidly dividing immune cells, leading to profound immunosuppression. **High-Yield NEET-PG Pearls:** * **Pregnancy** is a absolute contraindication for live vaccines (risk of teratogenicity). * **Exception in HIV:** In the WHO/Universal Immunization Program, **Measles** vaccine is given to HIV-infected children unless they are severely immunocompromised. * **Rule of Thumb:** Live vaccines should be delayed for at least **3 months** after stopping immunosuppressive therapy or chemotherapy.

Question 103: All of the following statements are true about the DPT vaccine EXCEPT:

A. It should be stored in a deep freezer. (Correct Answer)
B. Exposure to direct sunlight when in use should be avoided.
C. Stock supplies are needed for three months at the Primary Health Centre level.
D. A partially used vial should not be put back into the cold chain after the session.

Explanation: **Explanation:** The DPT vaccine is a **freeze-sensitive** vaccine. The correct answer is **Option A** because storing DPT in a deep freezer is contraindicated; freezing causes the aluminum adjuvant to precipitate, leading to a loss of potency and an increased risk of sterile abscesses at the injection site. **Analysis of Options:** * **Option A (Correct):** DPT must be stored in the **ILR (Ice-Lined Refrigerator)** at **+2°C to +8°C**, never in a deep freezer. If freezing is suspected, the "Shake Test" is performed to check for damage. * **Option B:** Like most vaccines, DPT is heat and light-sensitive. Exposure to direct sunlight can lead to the degradation of the toxoid components. * **Option C:** According to standard logistics in the Universal Immunization Programme (UIP), the PHC level is expected to maintain a stock of vaccines sufficient for **3 months**, while the sub-center level maintains a stock for one month. * **Option D:** Under the **Open Vial Policy**, multi-dose vials of DPT can be used for up to 28 days if specific criteria are met. However, the option refers to the traditional practice where a vial used in an outreach session (outside the cold chain) should be discarded to prevent contamination and maintain the cold chain's integrity. **High-Yield Facts for NEET-PG:** * **Freeze-Sensitive Vaccines:** DPT, TT, Hepatitis B, Pentavalent, and IPV (Mnemonic: **D**on't **F**reeze **H**is **P**recious **I**njections). * **Heat-Sensitive Vaccines:** OPV (most sensitive), followed by Measles/BCG. * **Shake Test:** Used only for freeze-sensitive vaccines (DPT, TT, Hep B) to determine if they have been damaged by sub-zero temperatures. * **Storage Level:** At the District level, vaccines are stored in Walk-in Coolers (WIC); at PHC level, in ILRs.

Question 104: What is the highest risk level for failure of cold chain maintenance in the public health system?

A. District hospitals
B. Primary Health Centers (PHCs)
C. Subcentre level (Correct Answer)
D. Community Health Centers (CHCs)

Explanation: ### Explanation The **cold chain** is a system of transporting and storing vaccines at recommended temperatures from the point of manufacture to the point of use. The risk of cold chain failure increases as we move from the central level toward the periphery. **Why Subcentre level is the correct answer:** The Subcentre represents the **farthest point (periphery)** of the vaccine delivery system. At this level, vaccines are usually stored for a very short duration in **vaccine carriers** rather than active refrigeration units like ILRs (Ice-Lined Refrigerators). The risk is highest here due to: 1. **Lack of continuous power supply** and dedicated cold chain equipment. 2. **Frequent opening** of vaccine carriers during outreach sessions. 3. **Human error** in maintaining ice packs (e.g., not using conditioned ice packs). 4. **Ambient temperature exposure** during field-level immunization. **Analysis of Incorrect Options:** * **District Hospitals, CHCs, and PHCs:** These levels are equipped with **Ice-Lined Refrigerators (ILRs)** and **Deep Freezers**. They have dedicated cold chain technicians, power backups (generators), and standardized temperature monitoring logs, making them significantly more secure than the Subcentre. **High-Yield Clinical Pearls for NEET-PG:** * **Weakest Link:** While the Subcentre has the highest risk of failure, the **Village level** (during actual administration) is often cited as the "weakest link" in the chain. * **ILR Temperature:** Most vaccines under UIP are stored between **+2°C to +8°C**. * **Most Heat Sensitive Vaccine:** Oral Polio Vaccine (OPV). * **Most Heat Resistant Vaccine:** Tetanus Toxoid (TT) / Td. * **Cold Chain Equipment at PHC:** The PHC is the lowest level where vaccines are stored for up to one month in an ILR.

Question 105: A 9-month-old, unimmunized child can be given which of the following vaccinations in a single visit?

A. BCG
B. DPT-1, OPV-1
C. DPT-1, OPV-1, Measles
D. BCG, DPT-1, OPV-1, Measles (Correct Answer)

Explanation: **Explanation:** The core concept tested here is the **National Immunization Schedule (NIS)** guidelines for "catch-up" immunization in an unimmunized child. **Why Option D is Correct:** According to the Universal Immunization Programme (UIP) in India, if a child presents for the first time at 9 months of age, they should receive all vaccines due at birth, 6, 10, and 14 weeks, plus the 9-month dose, provided there are no contraindications. * **BCG:** Can be given anytime up to 1 year of age. * **DPT & OPV:** The first doses (DPT-1, OPV-1) are initiated at this visit. * **Measles (MR-1):** The scheduled age for the first dose is 9 completed months. Administering these simultaneously at different injection sites is safe, effective, and prevents "missed opportunities" for immunization. **Analysis of Incorrect Options:** * **Option A & B:** These are incomplete. While these vaccines can be given, they ignore the fact that the child is also eligible for Measles (at 9 months) and BCG (up to 1 year). * **Option C:** This is also incomplete as it omits BCG. Since the child is under 1 year, BCG is still indicated to protect against childhood tuberculosis. **High-Yield NEET-PG Pearls:** 1. **BCG Limit:** BCG can be given up to **1 year** of age. Beyond 1 year, it is generally not recommended in the NIS. 2. **DPT Limit:** The DPT vaccine can be given up to **7 years** of age. 3. **OPV Limit:** OPV can be given up to **5 years** of age. 4. **Injection Sites:** When giving multiple injections, use different limbs (e.g., BCG in the left upper arm, DPT/Pentavalent in the anterolateral mid-thigh). 5. **Zero Dose:** OPV-0 is only given at birth; if the child is seen later, we start with OPV-1.

Question 106: Which of the following is known as the eighth day disease?

A. Puerperal tetanus
B. Tetanus neonatorum (Correct Answer)
C. Varicella
D. Measles

Explanation: **Explanation:** **Tetanus neonatorum** is known as the **"eighth day disease"** because symptoms typically manifest between the 3rd and 14th day after birth, with the majority of cases occurring around the **8th day**. It is caused by *Clostridium tetani* infection, usually due to unhygienic umbilical cord practices (the "3 Cs" violation: clean hands, clean surface, clean cord cut/tie). The incubation period is inversely related to the severity; the shorter the incubation, the higher the mortality. **Analysis of Options:** * **Puerperal tetanus:** This refers to tetanus occurring in the mother within 6 weeks of delivery or abortion. While related to the birthing process, it does not carry the "eighth day" moniker. * **Varicella (Chickenpox):** Known for its pleomorphic rash and "dewdrop on a rose petal" appearance. Its incubation period is typically 14–16 days. * **Measles:** Characterized by the prodromal triad (Cough, Coryza, Conjunctivitis) and Koplik's spots. It is not associated with the eighth-day timeline. **High-Yield Clinical Pearls for NEET-PG:** * **Elimination Status:** India achieved "Maternal and Neonatal Tetanus Elimination" (MNTE) in May 2015 (defined as <1 case per 1000 live births per district). * **Clinical Sign:** The earliest sign is often the **inability to suckle**, followed by muscular rigidity, spasms, and a characteristic "grimace" (risus sardonicus). * **Prevention:** Two doses of Tetanus Toxoid (TT/Td) during pregnancy and the promotion of institutional deliveries. * **Incubation Period Rule:** The "Rule of 8" is a useful mnemonic for the peak onset of neonatal tetanus.

Question 107: Which of the following statements about pulse polio immunization is false?

A. Mop-up immunization is done in restricted geographical areas.
B. It is carried out in all children less than 5 years of age.
C. Mopping up is done in areas where wild polio virus is found.
D. AFP surveillance is done in all children less than 5 years of age. (Correct Answer)

Explanation: **Explanation:** The correct answer is **D** because **AFP (Acute Flaccid Paralysis) surveillance is conducted in all children less than 15 years of age**, not 5 years. In some cases, it may even include adults if polio is strongly suspected. This is a critical distinction in the Global Polio Eradication Initiative to ensure no transmission is missed. **Analysis of Options:** * **Option A & C (Mop-up immunization):** These are correct statements. Mop-up rounds are "last-mile" strategies involving intensive door-to-door immunization. They are restricted to specific geographical areas where wild poliovirus is detected or where persistent transmission is suspected due to poor indicators. * **Option B (Pulse Polio Immunization):** This is correct. The Pulse Polio program targets all children aged **0–5 years** regardless of their previous immunization status to replace wild virus with vaccine virus in the community. **High-Yield NEET-PG Pearls:** * **AFP Surveillance Criteria:** The standard case definition is any child <15 years with sudden onset of flaccid paralysis or a person of any age if polio is suspected. * **Surveillance Indicators:** A sensitive system must detect at least **2 non-polio AFP cases per 100,000** children under 15 years. * **Stool Samples:** Two "adequate" stool samples must be collected 24–48 hours apart within 14 days of onset of paralysis. * **Zero Dose:** Refers to the dose of OPV given at birth. * **Pulse Polio Strategy:** Uses "National Immunization Days" (NIDs) to create a "pulse" of immunity.

Question 108: A PHC medical officer wants to give pulse polio immunization. Which finding in the Vaccine Vial Monitor (VVM) indicates that the vaccine should not be used?

A. Inner square is white, outer circle is blue
B. Inner square is blue but lighter than outer circle
C. Inner square matches the color of the outer circle (Correct Answer)
D. Inner square is lighter than outer circle

Explanation: ### Explanation The **Vaccine Vial Monitor (VVM)** is a heat-sensitive label placed on vaccine vials (most critically Oral Polio Vaccine) to monitor cumulative heat exposure over time. It consists of a heat-sensitive inner square inside a reference outer circle. **Why Option C is Correct:** The VVM works on the principle that the inner square darkens as it is exposed to heat. The **"Discard Point"** is reached when the inner square matches the color of the outer circle or becomes darker than it. At this stage, the vaccine has likely lost its potency due to heat degradation and **must not be used**, even if the expiry date has not passed. **Analysis of Incorrect Options:** * **Option A & D:** These represent **Stage 1**. If the inner square is white or significantly lighter than the outer circle, the vaccine is potent and safe to use. * **Option B:** This represents **Stage 2**. As long as the inner square is still lighter than the outer circle, the vaccine can still be used. However, it indicates the vaccine should be used first (Earliest Expiry First Out principle). **High-Yield NEET-PG Pearls:** * **VVM Stages:** Stages 1 & 2 are usable; Stages 3 & 4 (square matches or is darker than the circle) are unusable. * **OPV Sensitivity:** OPV is the most heat-sensitive vaccine. VVM was first introduced for OPV in 1996. * **VVM Location:** For OPV, the VVM is on the **cap** (to be discarded after opening). For other vaccines, it is on the **label** (to remain even after opening, supporting the Multi-Dose Vial Policy). * **The "Shake Test":** Remember, the VVM is for heat sensitivity. The Shake Test is used for damage due to **freezing** (DPT, TT, Hepatitis B).

Question 109: Which of the following statements is TRUE regarding polio?

A. Most of the cases are symptomatic.
B. Spastic paralysis is seen.
C. Intramuscular injections and increased muscular activity increase the risk of paralytic polio. (Correct Answer)
D. Pulse polio immunization is indicated in all children less than 3 years of age.

Explanation: ### Explanation **Correct Option: C** The phenomenon where intramuscular (IM) injections or intense physical exertion during the incubation period of poliovirus leads to paralysis is known as **Provocative Poliomyelitis**. IM injections (especially irritating substances like DPT) cause local inflammation and retrograde axonal transport of the virus from the muscle to the spinal cord, specifically targeting the motor neurons supplying that limb. Similarly, increased muscular activity increases the vascularity of the corresponding spinal cord segment, making it more susceptible to viral invasion. **Analysis of Incorrect Options:** * **Option A:** In reality, **90–95% of polio infections are asymptomatic** (inapparent). Only about 1% of cases progress to the paralytic stage, while the rest manifest as minor illness (abortive polio) or non-paralytic aseptic meningitis. * **Option B:** Polio causes **Flaccid Paralysis** (Lower Motor Neuron lesion), characterized by loss of muscle tone and absent deep tendon reflexes. Spastic paralysis is a feature of Upper Motor Neuron lesions. * **Option D:** Pulse Polio Immunization (PPI) in India is indicated for all children **less than 5 years of age**, regardless of their previous immunization status, to achieve herd immunity and interrupt viral transmission. **High-Yield Clinical Pearls for NEET-PG:** * **Most common strain:** Type 1 is most frequently associated with paralytic outbreaks. * **Last case in India:** Reported on January 13, 2011 (Howrah, West Bengal). India was declared Polio-free by the WHO in 2014. * **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 Sabin virus in the community. * **Cold Chain:** OPV is the most heat-sensitive vaccine and must be stored at -20°C for long-term storage.

Question 110: Which of the following is NOT true regarding the inactivated polio vaccine?

A. It produces circulatory antibodies.
B. It does not require stringent refrigeration.
C. It provides immunity against paralytic and wild strains. (Correct Answer)
D. It is not effective in an epidemic.

Explanation: The Inactivated Polio Vaccine (IPV), also known as the Salk vaccine, is a cornerstone of the Global Polio Eradication Initiative. Understanding its limitations compared to the Oral Polio Vaccine (OPV) is crucial for NEET-PG. ### **Explanation of the Correct Answer** **Option C is NOT true** because IPV primarily provides **humoral (systemic) immunity** but lacks the ability to induce significant **local intestinal (mucosal) immunity** (IgA). While IPV protects the individual from paralytic polio by preventing the virus from reaching the central nervous system, it does **not** prevent the wild poliovirus from multiplying in the gut. Consequently, a person vaccinated with IPV can still be subclinically infected and shed the wild virus in their feces, potentially spreading it to others. OPV is superior in this regard as it induces intestinal immunity, blocking the transmission of wild strains. ### **Analysis of Other Options** * **Option A (True):** IPV is administered parenterally and effectively induces circulating IgG, IgM, and IgA antibodies, providing excellent individual protection against viremia. * **Option B (True):** IPV is more heat-stable than OPV. While it still requires a cold chain (2°C to 8°C), it does not require the stringent freezing conditions (-20°C) necessary for long-term OPV storage. * **Option D (True):** In an epidemic, OPV is the vaccine of choice because it induces rapid intestinal immunity and facilitates "contact immunity" (secondary spread of vaccine virus), which helps break the chain of transmission. IPV cannot stop an ongoing outbreak. ### **High-Yield Clinical Pearls for NEET-PG** * **Fractional IPV (fIPV):** Administered intradermally (0.1 ml) at 6, 14 weeks, and 9 months under the Universal Immunization Programme (UIP) in India. * **VAPP vs. VDPV:** IPV carries **zero risk** of Vaccine-Associated Paralytic Polio (VAPP) or Vaccine-Derived Poliovirus (VDPV), unlike OPV. * **Salk vs. Sabin:** Remember **S**alk = **S**mart (Injected/Killed), **S**abin = **S**yrup (Oral/Live).

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

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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

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