Immunization and Vaccine-Preventable Diseases — MCQs

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

Question 181: Which of the following statements regarding Oral Polio Vaccine (OPV) is false?

A. Residual neuro-paralysis is a potential complication.
B. It is a killed vaccine. (Correct Answer)
C. Requires sub-zero temperatures for long-term storage.
D. It induces both intestinal and humoral immunity.

Explanation: ### Explanation **1. Why the Correct Answer is Right:** The statement "It is a killed vaccine" is **false** because the Oral Polio Vaccine (OPV), also known as the **Sabin vaccine**, is a **Live Attenuated Vaccine**. It contains live viruses that have been weakened (attenuated) so they cannot cause disease in healthy individuals but can still replicate to trigger an immune response. In contrast, the Inactivated Polio Vaccine (IPV), or Salk vaccine, is the killed version. **2. Analysis of Other Options:** * **Option A (Residual neuro-paralysis):** This is a **true** statement. Although rare, the live virus in OPV can undergo back-mutation, leading to **Vaccine-Associated Paralytic Poliomyelitis (VAPP)** or **Vaccine-Derived Poliovirus (VDPV)**, resulting in permanent paralysis. * **Option C (Sub-zero temperatures):** This is **true**. OPV is the most heat-sensitive vaccine in the Universal Immunization Programme (UIP). For long-term storage at the state/regional level, it must be kept at **-20°C**. At the PHC level, it is stored in the ILR at +2°C to +8°C for short durations. * **Option D (Intestinal and humoral immunity):** This is **true**. Because OPV is administered orally, it mimics natural infection. It induces **local mucosal immunity (IgA)** in the gut (preventing wild virus transmission) as well as **systemic humoral immunity (IgG)** in the blood. **3. NEET-PG High-Yield Pearls:** * **Vaccine Vial Monitor (VVM):** OPV was the first vaccine to use VVM to monitor heat exposure. * **Herd Immunity:** OPV provides herd immunity through "contact immunization" (secondary spread of the attenuated virus via feces), whereas IPV does not. * **Current Schedule:** Under India’s UIP, the schedule includes **bOPV** (0, 6, 10, 14 weeks + booster at 16-24 months) and **fractional IPV (fIPV)** (6, 14 weeks, and 9 months). * **Switch:** India switched from tOPV (trivalent) to bOPV (bivalent) in April 2016, removing the Type 2 strain.

Question 182: Which of the following statements regarding rabies management is untrue?

A. The wound should be thoroughly cleaned.
B. Suturing of the wound should be avoided initially.
C. Administration of anti-rabies serum is optional. (Correct Answer)
D. Anti-rabies vaccine should be administered.

Explanation: ### Explanation **1. Why the correct answer is right:** In the management of Category III rabies exposures (single/multiple transdermal bites or scratches), the administration of **Rabies Immunoglobulin (RIG) / Anti-rabies serum is NOT optional; it is mandatory.** RIG provides immediate passive immunity by neutralizing the virus at the wound site before the patient’s immune system can produce antibodies from the vaccine. Since rabies is 100% fatal once symptoms appear, omitting serum in high-risk exposures is a critical clinical error. **2. Analysis of incorrect options:** * **Option A (Wound cleaning):** This is the most crucial first step. Immediate flushing and washing of the wound with soap and water for at least 15 minutes can reduce the viral load by up to 80%. * **Option B (Suturing):** Suturing should be avoided or delayed for at least 48 hours to prevent "driving" the virus deeper into the nerve endings. If suturing is unavoidable, RIG must be infiltrated around the wound first. * **Option D (Vaccine administration):** Post-exposure prophylaxis (PEP) always includes a full course of the Anti-Rabies Vaccine (ARV) to induce active immunity, regardless of the category of exposure (except for Category I). **3. High-Yield Clinical Pearls for NEET-PG:** * **WHO Categories:** * **Category I:** Touching/feeding animals (No PEP). * **Category II:** Nibbling of uncovered skin, minor scratches (Vaccine only). * **Category III:** Single/multiple transdermal bites, licks on broken skin, or contact with bats (Vaccine + RIG). * **RIG Dosage:** Human RIG (HRIG) is 20 IU/kg; Equine RIG (ERIG) is 40 IU/kg. * **Site of Injection:** ARV is given Intramuscularly (Deltoid) or Intradermally (Updated Thai Red Cross regimen: 0, 3, 7, 28 days). **Never give ARV in the gluteal region** due to poor absorption. * **Observation Period:** The 10-day observation period applies only to healthy dogs/cats; treatment must start immediately and can be discontinued if the animal remains healthy.

Question 183: A wildlife officer presents for pre-exposure rabies vaccination. How many doses of HDCV (Human Diploid Cell Vaccine) are recommended for rabies pre-exposure prophylaxis?

A. 1
B. 2
C. 3 (Correct Answer)
D. 4

Explanation: ### Explanation **Correct Answer: C (3 doses)** **Medical Concept:** Pre-exposure prophylaxis (PrEP) for rabies is recommended for individuals at high risk of exposure, such as wildlife officers, veterinarians, and laboratory workers. According to the **WHO and National Guidelines (India)**, the standard intramuscular (IM) regimen for PrEP consists of **3 doses** of modern cell-culture vaccines (like HDCV or PCECV). The schedule is administered on **Days 0, 7, and 21 (or 28)**. The primary goal is to induce immunological memory and simplify post-exposure management by eliminating the need for Rabies Immunoglobulin (RIG). **Analysis of Options:** * **Option A (1 dose):** A single dose is insufficient to prime the immune system or create lasting memory cells. * **Option B (2 doses):** While some recent WHO updates discuss a 2-dose PrEP schedule (Days 0 and 7) for specific cost-effective public health strategies, the standard academic and clinical gold standard for exams remains the 3-dose regimen. * **Option D (4 doses):** This is the standard **Post-Exposure Prophylaxis (PEP)** schedule (Essen regimen: 0, 3, 7, 14) for immunocompetent individuals who have *not* been previously vaccinated. **High-Yield Clinical Pearls for NEET-PG:** * **Site of Injection:** Always the **Deltoid muscle** (adults) or anterolateral thigh (children). Never the gluteal region, as fat interferes with vaccine absorption. * **Re-exposure after PrEP:** If a previously vaccinated person (who completed the 3-dose PrEP) is bitten, they only need **2 booster doses** (Days 0 and 3). RIG is **not** required. * **Intradermal (ID) Route:** PrEP can also be given via the ID route (0.1 ml) on the same schedule (0, 7, 21/28) to save costs. * **HDCV:** It is considered the "Gold Standard" vaccine due to high immunogenicity and low adverse effects.

Question 184: Which of the following vaccines is NOT included in the National Immunization Programme?

A. Tetanus Toxoid (TT)
B. Hepatitis B (Correct Answer)
C. Oral Polio Vaccine (OPV)
D. Measles

Explanation: **Explanation:** The question asks to identify the vaccine **not** included in the National Immunization Programme (NIP). However, it is important to note that in the current Indian context, **all four options are actually part of the Universal Immunization Programme (UIP).** If this question appears in a competitive exam like NEET-PG, it is likely a **recalled/older question** or contains a technicality regarding nomenclature. Historically, Hepatitis B was the last of these four to be integrated into the national schedule (phased in from 2002-2011). 1. **Hepatitis B (Correct Option for this specific MCQ):** While now a core component of the UIP (given at birth, 6, 10, and 14 weeks), it was traditionally the "odd one out" in older textbooks compared to the original Expanded Programme on Immunization (EPI) vaccines. 2. **Tetanus Toxoid (TT):** This has been replaced by **Td (Tetanus and adult Diphtheria)** in the current UIP schedule for pregnant women and children (10 & 16 years) to provide continued protection against Diphtheria. 3. **Oral Polio Vaccine (OPV):** A cornerstone of the UIP, given as a birth dose and a primary series (6, 10, 14 weeks) along with fractional IPV. 4. **Measles:** Now administered as the **MR (Measles-Rubella)** vaccine at 9-12 months and 16-24 months. **High-Yield Clinical Pearls for NEET-PG:** * **Mission Indradhanush:** Launched to achieve 90% full immunization coverage. * **Pentavalent Vaccine:** Combines DPT, Hep B, and Hib (Haemophilus influenzae type b). * **Rotavirus Vaccine:** Now rolled out nationwide in the UIP. * **PCV (Pneumococcal Conjugate Vaccine):** The most recent major addition to the national schedule. * **Open Vial Policy:** Applies to Multi-dose vials of OPV, DPT, Hep B, Td, and IPV (but **not** to reconstituted vaccines like Measles/BCG).

Question 185: All of the following vaccinations are administered via the subcutaneous route, except:

A. Japanese encephalitis
B. Hepatitis B (Correct Answer)
C. Measles
D. MR

Explanation: **Explanation:** The route of administration for vaccines is determined by the vaccine's composition and the desired immune response. **Hepatitis B (Correct Answer):** This vaccine is administered via the **Intramuscular (IM)** route. In infants, it is given in the anterolateral aspect of the mid-thigh, while in adults, it is given in the deltoid muscle. It must never be given in the gluteal region due to the risk of injury to the sciatic nerve and lower immunogenicity (due to fatty tissue). Furthermore, Hepatitis B is an **adsorbed vaccine** (containing aluminum salts); if injected subcutaneously, it can cause local irritation, granulomas, or tissue necrosis. **Incorrect Options (Subcutaneous Vaccines):** * **Measles & MR (Measles-Rubella):** Under the Universal Immunization Programme (UIP), these live attenuated vaccines are strictly administered via the **Subcutaneous (SC)** route, usually in the right upper arm. * **Japanese Encephalitis (JE):** The live attenuated (SA-14-14-2) vaccine used in the national program is administered via the **Subcutaneous** route in the left upper arm. **High-Yield Clinical Pearls for NEET-PG:** * **Intradermal (ID) Vaccines:** BCG, Fractional IPV (fIPV), and Rabies (Post-exposure prophylaxis - Thai Red Cross regimen). * **Intramuscular (IM) Vaccines:** DPT, Pentavalent, Hepatitis B, TT/Td, and PCV. * **Oral Vaccines:** OPV and Rotavirus. * **Site Tip:** Most SC vaccines in the UIP are given in the upper arm, whereas most IM vaccines in infants are given in the **Anterolateral thigh** (Vastus lateralis).

Question 186: Which of the following vaccines is not contraindicated in pregnancy?

A. Rubella
B. Varicella
C. Hepatitis B (Correct Answer)
D. Measles

Explanation: **Explanation:** The core principle in obstetric immunization is the distinction between **Live-Attenuated Vaccines** and **Inactivated/Recombinant Vaccines**. **Why Hepatitis B is the Correct Answer:** Hepatitis B is a **subunit (recombinant) vaccine** containing only the HBsAg protein, not the live virus. It is non-infectious and does not pose a risk of vertical transmission or teratogenicity to the fetus. According to WHO and National Guidelines, Hepatitis B vaccination is **safe and indicated** during pregnancy if the mother is at high risk of infection (e.g., healthcare worker, multiple partners, or household contact with a carrier). **Why the Other Options are Incorrect:** * **Rubella, Varicella, and Measles (Options A, B, and D):** These are all **Live-Attenuated Vaccines**. There is a theoretical risk that the attenuated virus could cross the placenta and infect the developing fetus, potentially leading to congenital syndromes (e.g., Congenital Rubella Syndrome). Therefore, these are strictly **contraindicated** during pregnancy. Women are advised to avoid pregnancy for at least 4 weeks (1 month) after receiving these vaccines. **High-Yield NEET-PG Pearls:** * **Safe in Pregnancy:** Tdap (Tetanus, Diphtheria, Pertussis), Inactivated Influenza, Hepatitis B, and Rabies (post-exposure). * **Contraindicated in Pregnancy:** MMR (Measles, Mumps, Rubella), Varicella, Yellow Fever, and Oral Typhoid. * **Exception:** Yellow Fever vaccine may be given to a pregnant woman only if travel to an endemic area is unavoidable and the risk of disease outweighs the risk of vaccination. * **Post-partum:** All live vaccines (like MMR) can be safely administered immediately after delivery, even if the mother is breastfeeding.

Question 187: What adjuvant is used in the DPT vaccine?

A. Aluminium (Correct Answer)
B. Magnesium
C. Manganese
D. Silica

Explanation: **Explanation:** The correct answer is **Aluminium (Option A)**. In the DPT (Diphtheria, Pertussis, and Tetanus) vaccine, aluminium salts—specifically **Aluminium hydroxide or Aluminium phosphate**—are used as adjuvants. **Why Aluminium?** An adjuvant is a substance added to a vaccine to enhance the body's immune response to an antigen. Aluminium works through the **"Depot Effect"**: it sequesters the vaccine antigens at the injection site, allowing for a slow, sustained release. This prolonged exposure triggers a more robust activation of Antigen Presenting Cells (APCs) and a stronger antibody response, which is essential for inactivated vaccines like DPT. **Analysis of Incorrect Options:** * **B, C, and D (Magnesium, Manganese, Silica):** These elements are not used as adjuvants in human vaccines. While silica is sometimes used in experimental immunology research, it is not part of the standard DPT formulation. Magnesium and Manganese are essential minerals but lack the specific immunostimulatory properties required for vaccine stabilization. **High-Yield Clinical Pearls for NEET-PG:** * **Route of Injection:** Because DPT contains an aluminium adjuvant, it must be administered via **Deep Intramuscular (IM)** injection. If injected subcutaneously, the aluminium can cause local irritation, sterile abscesses, or "vaccination granulomas." * **Storage:** Vaccines with aluminium adjuvants (like DPT, TT, HepB, and Pentavalent) are **freeze-sensitive**. Freezing causes the adjuvant to precipitate, destroying the vaccine's potency. * **Shake Test:** If a DPT vial is suspected of being frozen, the "Shake Test" is performed to check for flocculation (clumping) of the aluminium adjuvant. * **Adjuvant in other vaccines:** Aluminium is also the standard adjuvant for Hepatitis B and Tetanus Toxoid (TT) vaccines.

Question 188: Which vaccine is considered safe during pregnancy?

A. Measles
B. Hepatitis B (Correct Answer)
C. BCG
D. Oral Polio Vaccine (OPV)

Explanation: **Explanation:** The fundamental principle in obstetric immunization is the distinction between **Live-Attenuated** and **Inactivated (Killed)** vaccines. **Why Hepatitis B is the correct answer:** Hepatitis B is a **subunit/recombinant vaccine** (inactivated). It does not contain live viral particles and, therefore, cannot replicate or cause disease in the mother or the fetus. It is considered safe and is specifically indicated during pregnancy for women at high risk of infection (e.g., healthcare workers or those with infected partners) to prevent vertical transmission. **Why the other options are incorrect:** * **Measles (Option A):** This is a **Live-Attenuated Viral vaccine**. Live vaccines are generally contraindicated in pregnancy due to the theoretical risk of the vaccine virus crossing the placenta and causing fetal infection or congenital defects. * **BCG (Option B):** This is a **Live-Attenuated Bacterial vaccine** (derived from *M. bovis*). It is contraindicated in pregnancy to avoid any systemic inflammatory response or potential fetal risk. * **OPV (Option D):** This is a **Live-Attenuated Viral vaccine**. While not strictly teratogenic, it is avoided in pregnancy unless there is an immediate epidemic risk. In routine practice, if polio vaccination is required, the Inactivated Polio Vaccine (IPV) is preferred. **High-Yield Clinical Pearls for NEET-PG:** 1. **Rule of Thumb:** All Live vaccines (Measles, Mumps, Rubella, Varicella, BCG, Yellow Fever) are **contraindicated** in pregnancy. 2. **The Exception:** Yellow Fever vaccine may be given to a pregnant woman if travel to an endemic area is unavoidable. 3. **Mandatory Vaccine:** Tetanus Toxoid (TT) or Tdap is the most important vaccine administered during pregnancy to prevent Neonatal Tetanus. 4. **Safe Vaccines:** Hepatitis B, Inactivated Influenza, and Rabies (post-exposure) are safe.

Question 189: A resident doctor, not immunized against Hepatitis B, sustains an accidental needle-stick injury from a patient positive for HBsAg. What is the recommended next step?

A. Administer hepatitis B immunoglobulin
B. Complete the course of hepatitis B vaccine
C. Administer hepatitis B immunoglobulin and complete the course of hepatitis B vaccine (Correct Answer)
D. Observation

Explanation: ### Explanation The management of a needle-stick injury (NSI) depends on the vaccination status of the healthcare worker (HCW) and the HBsAg status of the source. This scenario describes a **Post-Exposure Prophylaxis (PEP)** requirement for a non-immunized individual. **1. Why Option C is Correct:** When a non-immunized person is exposed to HBsAg-positive blood, they require **passive-active immunization**. * **Hepatitis B Immunoglobulin (HBIG):** Provides immediate, passive immunity to neutralize the virus before it infects hepatocytes. It should ideally be given within 24 hours (up to 7 days). * **Hepatitis B Vaccine:** Initiates active immunity for long-term protection. The first dose is given concurrently with HBIG (at a different anatomical site). **2. Why Other Options are Incorrect:** * **Option A:** HBIG alone provides only temporary protection. Without the vaccine series, the individual remains susceptible to future exposures. * **Option B:** The vaccine takes weeks to induce protective antibody titers ($\geq$10 mIU/mL). In an acute exposure, the "incubation window" is too short for the vaccine alone to prevent infection. * **Option D:** Observation is contraindicated due to the high risk of transmission (approx. 30% for HBsAg and HBeAg positive sources). **3. NEET-PG High-Yield Pearls:** * **Best Site for HBIG:** Deltoid or Gluteal muscle (different from the vaccine site). * **Best Site for Vaccine:** Deltoid (never gluteal in adults due to poor absorption). * **Non-Responder:** A person who fails to develop antibodies after two full 3-dose series. They require HBIG x 2 doses (one month apart) after exposure. * **Testing:** HCWs should be tested for Anti-HBs titers 1–2 months after completing the vaccine series. Protective level is **$\geq$10 mIU/mL**.

Question 190: Which of the following is NOT administered by the intradermal route?

A. BCG
B. Drug sensitivity injection
C. Mantoux test
D. Insulin (Correct Answer)

Explanation: **Explanation:** The correct answer is **Insulin**. The fundamental difference lies in the target tissue layer and the desired rate of absorption. **1. Why Insulin is the correct answer:** Insulin is administered via the **Subcutaneous (SC)** route, not intradermal. The subcutaneous fat layer has fewer blood vessels than muscle but more than the dermis, allowing for a slow, stable, and predictable absorption rate. If insulin were injected intradermally, absorption would be too slow and inconsistent; if injected intramuscularly, it would be absorbed too rapidly, risking hypoglycemia. **2. Analysis of Incorrect Options:** * **BCG (Bacillus Calmette-Guérin):** This is the classic example of an intradermal (ID) vaccine. It is administered over the left deltoid to induce a local delayed-type hypersensitivity reaction, leading to the characteristic scar. * **Drug Sensitivity Injection:** Skin prick or intradermal tests (e.g., for Penicillin) are performed to check for Type I Hypersensitivity. The dermis is highly immunologically active, making it the ideal site to observe a "wheal and flare" reaction. * **Mantoux Test:** This test uses PPD (Purified Protein Derivative) injected intradermally to screen for Tuberculosis infection by assessing the cell-mediated immune response. **3. High-Yield Clinical Pearls for NEET-PG:** * **Angle of Injection:** Intradermal injections are given at a shallow angle of **5–15 degrees** using a Tuberculin syringe. * **Fractional IPV (fIPV):** Under the Universal Immunization Programme (UIP), IPV is now administered **intradermally** (0.1 ml) at 6, 14 weeks, and 9 months to dose-spare and enhance mucosal immunity. * **Rabies Vaccine:** The Thai Red Cross regimen (IDRV) uses the intradermal route to reduce the cost of Post-Exposure Prophylaxis. * **Common SC Vaccines:** Measles/MR/MMR and Yellow Fever vaccines are administered via the subcutaneous route.

Practice by Chapter

Principles of Immunization

Practice Questions

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

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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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