Immunization and Vaccine-Preventable Diseases — MCQs

A 9-month-old child presents for the second dose of oral polio vaccine, two weeks after the first vaccination. The child has mild diarrhea, and the decision is made to defer further immunizations. Bacteriological examination of a stool culture is unremarkable; however, a small, single-stranded, positive RNA virus that is not inactivated by ether is isolated from the specimen. Which of the following viruses was most likely isolated?

Q260Easy

Measles vaccine contains the following as a preservative?

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

Question 251: Administration of which vaccine can result in paralysis in children?

A. Sabin polio vaccine (Correct Answer)
B. Measles vaccine
C. DT vaccine
D. DPT vaccine

Explanation: **Explanation:** The correct answer is **Sabin polio vaccine (Oral Polio Vaccine - OPV)**. **Why Sabin vaccine is the correct answer:** The Sabin vaccine is a **Live Attenuated Vaccine**. Because it contains a weakened but live virus, it can rarely undergo back-mutation or genetic reversion to a neurovirulent form. This leads to a condition known as **Vaccine-Associated Paralytic Poliomyelitis (VAPP)**. VAPP clinically mimics paralytic poliomyelitis caused by the wild poliovirus. It occurs more frequently in the first dose and in immunocompromised children. Additionally, prolonged circulation of the vaccine virus in under-immunized communities can lead to **Vaccine-Derived Polioviruses (VDPV)**, which also cause paralysis. **Why the other options are incorrect:** * **Measles vaccine:** A live attenuated vaccine, but its primary rare serious adverse events are febrile seizures or Toxic Shock Syndrome (if contaminated); it does not cause paralysis. * **DT vaccine:** A toxoid vaccine (Diphtheria and Tetanus). It is generally safe; common side effects are local soreness or fever. * **DPT vaccine:** A combination vaccine. While the Pertussis component is associated with rare neurological complications like encephalopathy or febrile convulsions, it does not cause flaccid paralysis. **High-Yield Clinical Pearls for NEET-PG:** * **Salk Vaccine (IPV):** An inactivated (killed) vaccine; it **cannot** cause VAPP because the virus is dead. * **VAPP Risk:** Estimated at 1 case per 3.8 million doses of OPV. * **Switch Strategy:** To eliminate the risk of VDPV type 2, India switched from Trivalent OPV (tOPV) to **Bivalent OPV (bOPV)** and introduced **Fractional IPV (fIPV)** into the routine schedule. * **Cold Chain:** OPV is the most heat-sensitive vaccine and must be stored at -20°C for long-term storage.

Question 252: Pneumococcal vaccination is indicated in which of the following conditions?

A. Postsplenectomy (Correct Answer)
B. Sickle cell anemia
C. HIV
D. After radiotherapy

Explanation: **Explanation:** **1. Why Postsplenectomy is the Correct Answer:** The spleen is the primary organ responsible for filtering encapsulated bacteria from the bloodstream and producing opsonizing antibodies. Patients who are asplenic (post-splenectomy) or have functional asplenia are at a high risk for **Overwhelming Post-Splenectomy Infection (OPSI)**. The most common and lethal causative organism is *Streptococcus pneumoniae*. Therefore, pneumococcal vaccination is a mandatory, life-saving indication in these patients to prevent invasive pneumococcal disease. **2. Analysis of Other Options:** * **Sickle Cell Anemia (B):** While patients with Sickle Cell Anemia do require pneumococcal vaccination due to functional asplenia (splenic infarction), in the context of standard NEET-PG questioning, **Postsplenectomy** is considered the "most classic" and absolute indication among the choices provided. * **HIV (C):** HIV patients are immunocompromised and are recommended to receive the vaccine, but it is a secondary indication compared to the anatomical absence of the spleen. * **After Radiotherapy (D):** Radiotherapy itself is not a direct indication for pneumococcal vaccination unless it results in significant splenic damage or is part of a pre-transplant conditioning regimen. **3. High-Yield Clinical Pearls for NEET-PG:** * **Timing:** For elective splenectomy, vaccinate **2 weeks before** surgery. For emergency splenectomy, vaccinate **2 weeks after** surgery (to ensure an adequate immune response). * **The "Big Three" Vaccines:** Post-splenectomy patients must be immunized against the three main encapsulated organisms: *S. pneumoniae*, *Haemophilus influenzae* type b (Hib), and *Neisseria meningitidis*. * **Vaccine Types:** Usually, a combination of PCV13 (Conjugate) followed by PPSV23 (Polysaccharide) is recommended for maximum coverage.

Question 253: When was Mission Indradhanush launched?

A. January 2005
B. July 2010
C. December 2014 (Correct Answer)
D. March 2016

Explanation: **Explanation:** **Correct Answer: C. December 2014** **Mission Indradhanush (MI)** was launched by the Ministry of Health and Family Welfare (MoHFW), Government of India, on **December 25, 2014** (Good Governance Day). The primary objective was to achieve full immunization coverage (FIC) of at least 90% for children up to 2 years of age and pregnant women who were either unvaccinated or partially vaccinated under the Universal Immunization Programme (UIP). It specifically targeted high-risk and "low-coverage" pockets to reduce vaccine-preventable diseases (VPDs). **Analysis of Incorrect Options:** * **A. January 2005:** This period is associated with the groundwork for the National Rural Health Mission (NRHM), which was officially launched in April 2005. * **B. July 2010:** This does not correspond to any major national immunization milestone. However, 2011 was the year India reported its last case of Polio. * **D. March 2016:** This was the period during which the Rotavirus vaccine was introduced into the UIP in a phased manner, but it is not the launch date of MI. **High-Yield Clinical Pearls for NEET-PG:** * **The "7" Colors:** Originally, MI targeted seven diseases: Diphtheria, Pertussis, Tetanus, Polio, Tuberculosis, Measles, and Hepatitis B. (Note: Japanese Encephalitis and *Haemophilus influenzae* type B were later included in select districts). * **Intensified Mission Indradhanush (IMI):** Launched in **October 2017** to further accelerate the reach. * **IMI 5.0 (2023):** The latest phase specifically focuses on increasing Measles-Rubella (MR) elimination efforts and ensuring no child is left behind before the U-WIN digital platform rollout. * **Target:** MI focuses on the "unreached" population in urban slums and migratory settlements.

Question 254: Which of the following vaccines is MOST sensitive to heat?

A. Measles
B. BCG
C. OPV (Correct Answer)
D. IPV

Explanation: ### Explanation **Correct Option: C (OPV)** The Oral Polio Vaccine (OPV) is the **most heat-sensitive** vaccine in the entire immunization program. It is highly thermolabile and requires strict maintenance of the cold chain at -20°C for long-term storage. To monitor its potency, each vial is equipped with a **Vaccine Vial Monitor (VVM)**, which changes color when exposed to cumulative heat. **Analysis of Incorrect Options:** * **A. Measles:** While measles is a live-attenuated vaccine and is heat-sensitive, it is more stable than OPV. It must be stored at +2°C to +8°C and is highly sensitive to **light** (photo-sensitive). * **B. BCG:** BCG is also a live-attenuated vaccine. It is relatively heat-sensitive but significantly more stable than OPV. Like measles, it is highly sensitive to sunlight. * **C. IPV:** Inactivated Polio Vaccine (IPV) is more heat-stable than its oral counterpart (OPV) because it contains killed virus particles rather than live-attenuated ones. **High-Yield Clinical Pearls for NEET-PG:** * **Hierarchy of Heat Sensitivity:** (Most Sensitive) **OPV > Measles > BCG > DPT > DT > TT** (Least Sensitive/Most Heat Stable). * **Freeze Sensitivity:** While OPV is the most heat-sensitive, the **Hepatitis B** and **DPT/Pentavalent** vaccines are the most **freeze-sensitive**. They must never be frozen (the "Shake Test" is used to check if they have been damaged by freezing). * **Storage:** At the PHC level, all vaccines (including OPV and Measles) are stored in the **ILR (Ice-Lined Refrigerator)** at +2°C to +8°C for short-term use. * **Reconstitution Rule:** BCG and Measles vaccines must be used within **4 hours** of reconstitution; otherwise, they must be discarded due to the risk of Toxic Shock Syndrome (Staphylococcal contamination).

Question 255: What is the ideal storage temperature for the DPT vaccine?

A. Room temperature
B. 4 to 8°C (Correct Answer)
C. 0 to -20°C
D. None of the above

Explanation: **Explanation:** The **DPT (Diphtheria, Pertussis, and Tetanus)** vaccine is a liquid-formulated, adsorbed vaccine. To maintain its potency and safety, it must be stored in the **Cold Chain** at a temperature range of **+2°C to +8°C** (with +4°C to +8°C being the ideal operating range in most clinical settings). **Why Option B is Correct:** DPT is a **freeze-sensitive vaccine**. The vaccine contains aluminum salts as adjuvants. If the temperature drops below 0°C, these salts crystallize, causing the vaccine to lose its potency and potentially increasing the risk of sterile abscesses at the injection site. Therefore, it must be kept in the refrigerator (ILR) but never in the freezer. **Why Other Options are Incorrect:** * **Option A (Room Temperature):** Vaccines are biological products that undergo rapid thermal degradation at room temperature. DPT loses its pertussis component's potency if exposed to heat for prolonged periods. * **Option C (0 to -20°C):** This is the storage temperature for **freeze-tolerant** vaccines like OPV and Yellow Fever. Storing DPT at these temperatures would cause irreversible damage due to freezing. **High-Yield Clinical Pearls for NEET-PG:** * **The Shake Test:** If you suspect a DPT, TT, or Hepatitis B vial has been frozen, perform the "Shake Test." A frozen vaccine will show rapid sedimentation and large flakes compared to a control vial. * **Storage Location:** In a top-opening Ice-Lined Refrigerator (ILR), DPT should be stored in the **top/middle baskets**, away from the bottom (coldest part) to prevent accidental freezing. * **Heat Sensitivity:** Among the DPT components, **Pertussis** is the most heat-sensitive, while **Tetanus** is the most heat-stable. * **Open Vial Policy:** Under the Universal Immunization Programme (UIP), multi-dose vials of DPT can be used for up to **28 days** after opening, provided they are stored at +2°C to +8°C and have not expired or been contaminated.

Question 256: What is the duration of validity of yellow fever vaccination?

A. 2 years
B. 5 years
C. 10 years (Correct Answer)
D. 12 years

Explanation: ### Explanation **Correct Answer: C. 10 years** **1. Why 10 years is the correct answer:** According to the **International Health Regulations (IHR)**, the validity of a Yellow Fever vaccination certificate traditionally begins **10 days** after primary vaccination and lasts for a period of **10 years**. For the purpose of the NEET-PG exam, the standard legal validity remains 10 years. However, it is crucial to note that in 2014, the WHO updated the IHR to state that a single dose provides life-long immunity; while this change is adopted clinically, the "10-year" rule is still the most frequently tested benchmark in competitive exams regarding the certificate's legal duration. **2. Why the other options are incorrect:** * **A (2 years):** This is too short. No major live-attenuated vaccine requires a booster at such a frequent interval for travel purposes. * **B (5 years):** This duration is not associated with Yellow Fever. It is more commonly associated with the older requirements for the Meningococcal vaccine (ACYW-135) for Hajj pilgrims. * **D (12 years):** There is no physiological or regulatory basis for a 12-year validity period in immunization schedules. **3. High-Yield Clinical Pearls for NEET-PG:** * **Type of Vaccine:** Live attenuated (17D strain). * **Route & Dose:** Subcutaneous (0.5 ml). * **Storage:** Must be stored between **-30°C and +5°C** (highly heat-sensitive). * **Contraindications:** Infants <6 months, pregnancy (except during outbreaks), symptomatic HIV/AIDS, and individuals with **egg allergy** (as the virus is grown in chick embryos). * **International Travel:** India requires a valid certificate from travelers arriving from endemic zones (Africa and South America). If a traveler lacks a certificate, they are kept in **quarantine for 6 days** (the incubation period of the disease).

Question 257: In which muscle is the cell culture Rabies vaccine typically administered?

A. Medial aspect of the thigh
B. Deltoid muscle (Correct Answer)
C. Anterior abdomen
D. Lateral aspect of the thigh

Explanation: **Explanation:** The **Deltoid muscle** is the preferred site for intramuscular (IM) administration of modern Cell Culture Rabies Vaccines (CCVs) in adults and older children. This is because the deltoid region provides optimal vaccine absorption and immunogenicity. Clinical studies have shown that administration in this site produces significantly higher neutralizing antibody titers compared to other sites. **Analysis of Options:** * **Deltoid Muscle (Correct):** It is the standard site for IM rabies vaccination. In infants and small children, the **anterolateral aspect of the thigh** is used instead of the deltoid. * **Medial aspect of the thigh (Incorrect):** This area contains major neurovascular structures (femoral vessels) and is never used for vaccinations. * **Anterior abdomen (Incorrect):** This was the site for the older, obsolete Neural Tissue Vaccines (NTV/Semple vaccine), which required large volumes (5ml) injected subcutaneously. Modern CCVs must **never** be given in the abdominal wall. * **Lateral aspect of the thigh (Incorrect):** While the *anterolateral* thigh is used in infants, the *lateral* aspect is not the specific anatomical landmark taught for immunization. **High-Yield Clinical Pearls for NEET-PG:** 1. **Gluteal Region Contraindication:** Rabies vaccine should **never** be administered in the gluteal region (buttocks). The presence of thick adipose tissue can lead to poor absorption and lower seroconversion rates, potentially leading to vaccine failure. 2. **Route:** CCVs can be given via the **Intramuscular (IM)** route (Essen or Zagreb schedule) or the **Intradermal (ID)** route (Updated Thai Red Cross schedule). 3. **Dose:** The IM dose is 0.5 ml or 1 ml (depending on the brand), whereas the ID dose is consistently 0.1 ml per site.

Question 258: A few months after receiving an intramuscular injection, a patient presented with pain in both shoulders. On examination, there is sensory loss over the bilateral shoulders with mild wasting of muscles. Which of the following vaccines is the likely cause?

A. Tetanus (Correct Answer)
B. Measles
C. MMR
D. BCG

Explanation: ### **Explanation** The clinical presentation described—bilateral shoulder pain, sensory loss, and muscle wasting following an intramuscular injection—is characteristic of **Brachial Neuritis** (also known as Parsonage-Turner Syndrome or Neuralgic Amyotrophy). **1. Why Tetanus is the Correct Answer:** Tetanus toxoid (TT) is the vaccine most frequently associated with brachial neuritis. It is a known, though rare, neurological complication occurring typically within days to weeks after administration. The pathogenesis is believed to be an **immune-mediated inflammatory reaction** (Type III hypersensitivity) against the toxoid, leading to inflammation of the brachial plexus. While often unilateral, it can present bilaterally. **2. Analysis of Incorrect Options:** * **Measles & MMR:** These are live-attenuated vaccines usually administered **subcutaneously**. While they can rarely cause systemic neurological issues like Subacute Sclerosing Panencephalitis (SSPE) or idiopathic thrombocytopenic purpura (ITP), they are not classically associated with localized brachial neuritis. * **BCG:** This vaccine is administered **intradermally** (usually over the left deltoid). Its common complications are local, such as BCG lymphadenitis or cold abscess formation, rather than plexopathy. **3. NEET-PG High-Yield Pearls:** * **Most common side effect of TT:** Local pain and swelling (Arthus-type reaction). * **Injection Site:** TT should be given intramuscularly (IM) in the deltoid. * **Cold Chain:** TT is highly sensitive to freezing; if frozen, the vaccine is damaged (Shake Test is used to check). * **Contraindication:** A history of brachial neuritis or a severe hypersensitivity reaction following a previous dose is a precaution/contraindication for further TT doses.

Question 259: A 9-month-old child presents for the second dose of oral polio vaccine, two weeks after the first vaccination. The child has mild diarrhea, and the decision is made to defer further immunizations. Bacteriological examination of a stool culture is unremarkable; however, a small, single-stranded, positive RNA virus that is not inactivated by ether is isolated from the specimen. Which of the following viruses was most likely isolated?

A. Adenovirus
B. Hepatitis C
C. Parvovirus B19
D. Poliovirus (Correct Answer)

Explanation: **Explanation:** The correct answer is **D. Poliovirus**. This question tests the integration of clinical immunization schedules with the microbiological characteristics of the vaccine virus. **Why Poliovirus is correct:** The child recently received the first dose of the **Oral Polio Vaccine (OPV)**, which contains live-attenuated Sabin strains. These viruses replicate in the oropharynx and intestine and are excreted in the feces for several weeks. * **Microbiology:** Poliovirus belongs to the *Picornaviridae* family. It is a **small (27-30 nm), single-stranded, positive-sense RNA virus**. * **Ether Resistance:** Because it is **non-enveloped (naked)**, it is resistant to lipid solvents like ether, which only inactivate enveloped viruses. * **Clinical Context:** Mild diarrhea is not a contraindication for OPV, but the virus isolated is clearly the vaccine strain being shed. **Why other options are incorrect:** * **A. Adenovirus:** While it causes diarrhea and is non-enveloped, it is a **double-stranded DNA** virus. * **B. Hepatitis C:** Although it is a positive-sense RNA virus, it is **enveloped**, meaning it would be inactivated by ether. * **C. Parvovirus B19:** This is a **single-stranded DNA** virus (the only one of clinical importance). **High-Yield Pearls for NEET-PG:** 1. **OPV Shedding:** Vaccine virus can be excreted in stools for 4–6 weeks, contributing to "contact immunity" in the community. 2. **Ether Sensitivity Test:** Used to differentiate viruses; **Enveloped viruses** (e.g., HIV, Herpes, HBV) are ether-sensitive, while **Non-enveloped viruses** (e.g., Polio, HAV, HEV) are ether-resistant. 3. **Contraindications:** Minor respiratory infections or diarrhea are **NOT** contraindications for immunization. 4. **Pulse Polio:** Uses bOPV (Type 1 and 3) to eliminate the risk of VDPV2 (Vaccine-Derived Poliovirus Type 2).

Question 260: Measles vaccine contains the following as a preservative?

A. Streptomycin
B. Chloramphenicol
C. Neomycin (Correct Answer)
D. Thiomersal

Explanation: **Explanation:** The Measles vaccine is a **live-attenuated viral vaccine** (Edmonston-Zagreb strain). To prevent bacterial contamination during the manufacturing process and storage, small amounts of antibiotics are added as preservatives/stabilizers. **Why Neomycin is the correct answer:** Neomycin is the standard preservative used in the Measles, Mumps, and Rubella (MMR) vaccines. It is effective against a broad spectrum of bacteria but does not interfere with the replication of the live virus. * **Clinical Significance:** This is why a history of **anaphylaxis to Neomycin** is a contraindication for the Measles vaccine. **Analysis of Incorrect Options:** * **Streptomycin & Chloramphenicol:** These are generally not used as preservatives in modern vaccines due to their side-effect profiles (e.g., ototoxicity or bone marrow suppression) and the risk of hypersensitivity. * **Thiomersal (Thimerosal):** This is a mercury-based preservative used in **killed/inactivated vaccines** (like multi-dose vials of DPT, Hepatitis B, and TT). It is **never** used in live vaccines like Measles because it would kill the live virus, rendering the vaccine ineffective. **High-Yield NEET-PG Pearls:** 1. **Reconstitution:** Measles vaccine is heat-sensitive and lyophilized (freeze-dried). It must be reconstituted with **Sterile Water** (Diluent). 2. **Storage:** Once reconstituted, it must be used within **4 hours** or discarded to prevent toxic shock syndrome (usually caused by *S. aureus* contamination). 3. **Administration:** Dose is **0.5 ml**, given **Subcutaneously (SC)** at the right upper arm. 4. **Schedule:** 1st dose at 9 completed months; 2nd dose at 16–24 months (under India’s NIS).

Practice by Chapter

Principles of Immunization

Practice Questions

Types of Vaccines

Practice Questions

Universal Immunization Program

Practice Questions

Cold Chain System

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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

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New and Underutilized Vaccines

Practice Questions

Vaccination Coverage Assessment

Practice Questions

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