Immunization and Vaccine-Preventable Diseases Practice Questions

Q: For how long can vaccines be stored at a Primary Health Centre (PHC)?

30 days. ### Explanation **Correct Answer: D. 30 days** In the Indian Universal Immunization Programme (UIP) cold chain system, the duration of vaccine storage is determined by the level of the healthcare facility. A **Primary Health Centre (PHC)** is equipped with an **Ice-Lined Refrigerator (ILR)** and a Deep Freezer (small). According to standard guidelines, vaccines can be stored at the PHC level for a maximum of **one month (30 days)**. This duration ensures a balance between maintaining vaccine potency and managing supply logistics from the district level. **Analysis of Incorrect Options:** * **A & B (2 days / 7 days):** These durations are too short for a PHC. However, 48–72 hours is the typical duration vaccines are kept in **vaccine carriers** during outreach sessions or "sub-centre" activities. * **C (15 days):** While some regional guidelines previously suggested shorter intervals, the standard UIP protocol for PHCs remains 30 days. 15 days is not a standard benchmark for any specific level of the cold chain. **High-Yield Clinical Pearls for NEET-PG:** * **Storage Levels & Durations:** * **Regional/State Level (GMSD):** 3 months. * **District Level:** 1 month. * **PHC Level:** 1 month. * **Sub-centre/Session Site:** 48–72 hours (in vaccine carriers). * **Temperature Maintenance:** At the PHC, ILRs maintain a temperature of **+2°C to +8°C**, which is ideal for most vaccines (including Tseries, HepB, and DPT). * **The "Shake Test":** Used to determine if a freeze-sensitive vaccine (like DPT, TT, or Pentavalent) has been damaged by sub-zero temperatures. * **Most Heat Sensitive Vaccine:** Oral Polio Vaccine (OPV). * **Most Heat Resistant Vaccine:** Tetanus Toxoid (TT).

Q: Who among the following discovered smallpox vaccination?

Edward Jenner. **Explanation:** The correct answer is **Edward Jenner (Option C)**. In 1796, Jenner observed that milkmaids who had contracted cowpox (a milder disease) appeared immune to smallpox. He tested this hypothesis by inoculating a young boy, James Phipps, with material from a cowpox lesion and subsequently exposing him to smallpox. The boy did not develop the disease. This pioneered the concept of **vaccination** (derived from the Latin word *vacca*, meaning cow). Jenner is widely regarded as the "Father of Immunology." **Analysis of Incorrect Options:** * **John Hunter (A):** A renowned British surgeon and teacher to Edward Jenner. While he made significant contributions to anatomy and surgery, he did not discover the smallpox vaccine. * **Louis Pasteur (B):** Known as the "Father of Microbiology," Pasteur developed vaccines for **Rabies, Anthrax, and Fowl Cholera**. He also formulated the Germ Theory of Disease and the process of pasteurization. * **James Lind (D):** A Scottish physician who conducted one of the first clinical trials and discovered that citrus fruits (Vitamin C) could cure and prevent **Scurvy**. **High-Yield Clinical Pearls for NEET-PG:** * **Smallpox Eradication:** Smallpox is the only human infectious disease to be eradicated. * **Last Case:** The last naturally occurring case was reported in **Somalia (1977)**. * **Global Eradication:** Officially declared by the WHO on **May 8, 1980**. * **Last Case in India:** Reported in **1975** (Bihar). India was declared smallpox-free in 1977. * **Bifurcated Needle:** The specific tool used for the "multiple puncture" technique in smallpox vaccination.

Q: If convulsions are present, which vaccine should not be administered?

DPT. **Explanation:** The correct answer is **DPT (Diphtheria, Pertussis, and Tetanus)**. The primary reason for this contraindication is the **Whole-cell Pertussis (wP)** component of the vaccine. Pertussis antigens are known to be neurotoxic and can trigger neurological complications, including febrile seizures, encephalopathy, or prolonged convulsions. **Why DPT is the correct answer:** In clinical practice, a history of uncontrolled seizures, progressive neurological disorders, or an evolving neurological condition is a **strict contraindication** for the pertussis component. If a child has a history of convulsions, the "Triple Vaccine" (DPT) is withheld and replaced with **DT (Diphtheria and Tetanus)** to avoid aggravating the neurological state. **Why other options are incorrect:** * **Oral Polio (OPV):** This is a live attenuated vaccine. Its primary contraindications are immunodeficiency states (e.g., HIV, hypogammaglobulinemia) or household contact with an immunocompromised person. It has no association with convulsions. * **BCG:** This is contraindicated in individuals with generalized eczema, skin infections at the site of injection, or severe immunodeficiency. It does not affect the central nervous system. * **Tetanus Toxoid (TT):** TT is generally safe. It is the pertussis component in the DPT combination that is the culprit, not the tetanus component. **High-Yield Clinical Pearls for NEET-PG:** * **Absolute Contraindication for Pertussis:** Encephalopathy within 7 days of a previous dose. * **Alternative:** In children with a history of seizures where pertussis coverage is still desired, **acellular Pertussis (aP)** is preferred over whole-cell (wP) as it has a significantly lower risk of febrile seizures. * **DT vs. DPT:** If a child is over 7 years old or has neurological contraindications, the Pertussis component is dropped, and DT/Td is administered.

Q: What is the threshold level of herd immunity for Pertussis?

90%. **Explanation:** **1. Why 90% is Correct:** Herd immunity (community immunity) is the resistance of a group to the spread of an infectious disease based on the proportion of immune individuals. The threshold level required to stop transmission depends on the **Basic Reproduction Number ($R_0$)**—the number of secondary cases produced by one case in a susceptible population. Pertussis (Whooping Cough) is highly contagious, with an $R_0$ typically ranging from **12 to 17**. Using the formula $H = 1 - (1/R_0)$, a very high percentage of the population must be immune to achieve herd effect. For Pertussis, this threshold is approximately **90–95%**. **2. Analysis of Incorrect Options:** * **80% (Option A):** This is the threshold for diseases with lower infectivity, such as **Polio** (approx. 80%) or **Diphtheria** (approx. 85%). * **70% (Option B):** This level is insufficient for most highly communicable childhood diseases. It is closer to the threshold estimated for some strains of Influenza or the initial targets for Rubella. * **50% (Option C):** This is far below the requirement for any major vaccine-preventable disease (VPD) spread by respiratory droplets. **3. High-Yield Clinical Pearls for NEET-PG:** * **Measles** has the highest $R_0$ (12–18) and requires the highest herd immunity threshold (**94–97%**). * **Pertussis** is unique because vaccine-induced immunity wanes over time, making high coverage even more critical. * **Herd immunity does not apply to Tetanus**, as it is not transmitted from person to person (non-communicable). * **Formula for Herd Immunity Threshold ($H$):** $1 - (1/R_0)$. If $R_0$ increases, the required herd immunity also increases.

Q: BCG vaccination is administered by which route?

Intradermal. **Explanation:** The **BCG (Bacillus Calmette-Guérin)** vaccine is a live attenuated vaccine derived from *Mycobacterium bovis*. It is administered via the **Intradermal (ID)** route, specifically over the left deltoid muscle. **Why Intradermal?** The intradermal route is chosen because it allows for a slow, localized release of the antigen, which is essential for stimulating a strong **Cell-Mediated Immunity (CMI)**. This route leads to the characteristic formation of a wheal, followed by a papule, shallow ulcer, and eventually a permanent scar. Administering it deeper can lead to complications like regional lymphadenitis or abscess formation. **Analysis of Incorrect Options:** * **Subcutaneous (A):** This route is typically used for vaccines like Measles/MRSA and Yellow Fever. If BCG is given subcutaneously, it increases the risk of local abscesses and severe lymphadenopathy. * **Intramuscular (C):** Used for killed/subunit vaccines like DPT, Hep B, and TT. BCG is never given IM as it would bypass the necessary dermal immune response. * **Subdermal (D):** This is not a standard clinical route for immunization. **High-Yield Clinical Pearls for NEET-PG:** * **Dose:** 0.05 ml for neonates (below 4 weeks) and 0.1 ml for infants above 4 weeks. * **Syringe:** A specialized **Tuberculin/Omega syringe** with a 26G needle is used. * **Diluent:** Normal Saline (NS) is the only recommended diluent. * **Site:** Left deltoid (standardized globally to avoid confusion with other scars). * **Phenomenon:** The "BCG scar" is the hallmark of successful vaccination. If a child develops a scar within 48 hours, it suggests **"Accelerated BCG reaction,"** indicating the child may already be infected with TB.

Q: Which vaccine is used for the prevention of Japanese Encephalitis?

JEV vaccine. **Explanation:** **Japanese Encephalitis (JE)** is a leading cause of viral encephalitis in Asia, transmitted by the *Culex* mosquito. The correct answer is the **JEV vaccine**, which is specifically designed to provide immunity against the Japanese Encephalitis virus. * **Why JEV Vaccine is Correct:** In India, under the Universal Immunization Programme (UIP), the live attenuated **SA-14-14-2 strain** (derived from primary hamster kidney cells) is used. It is administered subcutaneously in two doses: the first at 9 months (with MR-1) and the second at 16–24 months (with DPT booster). **Analysis of Incorrect Options:** * **Dengvaxia:** This is the first licensed vaccine for **Dengue**, not JE. While both are Flaviviruses, they require specific antigens for protection. * **BCG (Bacillus Calmette-Guérin):** A live bacterial vaccine used to prevent severe forms of **Tuberculosis** (like TB meningitis and miliary TB). * **Hepatitis B Vaccine:** A subunit (recombinant) vaccine used to prevent **Hepatitis B virus** infection and its complications, such as cirrhosis and hepatocellular carcinoma. **High-Yield Clinical Pearls for NEET-PG:** * **Vector:** *Culex tritaeniorhynchus* (breeds in rice fields). * **Reservoir/Amplifier Host:** Pigs (Ardeid birds are the natural reservoir). * **Vaccine Strains:** Apart from the live SA-14-14-2, inactivated vaccines like **JENVAC** (indigenous) and **IXIARO** are also available. * **UIP Schedule:** JE vaccine is only administered in **endemic districts** (currently ~216 districts in India). * **Key Contraindication:** Pregnancy and immunocompromised states (for the live attenuated version).

Question 1

For how long can vaccines be stored at a Primary Health Centre (PHC)?

Accepted Answer

30 days

Answer

2 days

Answer

7 days

Answer

15 days

Question 2

Which vaccines are contraindicated in an HIV-positive child?

Accepted Answer

Oral Polio Vaccine (OPV)

Answer

Measles, Mumps, and Rubella (MMR) vaccine

Answer

Rabies vaccine

Answer

Influenza vaccine

Question 3

Who among the following discovered smallpox vaccination?

Accepted Answer

Edward Jenner

Answer

John Hunter

Answer

Louis Pasteur

Answer

James Lind

Question 4

Which of the following statements about pertussis is false?

Accepted Answer

Maternal antibodies provide protection in infants and fomites play a small role in the spread of the disease.

Answer

Fomites play a small role in the spread of the disease.

Answer

Maternal antibodies provide protection in infants and the disease is commonly seen in infants.

Question 5

If convulsions are present, which vaccine should not be administered?

Accepted Answer

DPT

Answer

Oral Polio

Answer

BCG

Answer

Tetanus toxoid

Question 6

What is the threshold level of herd immunity for Pertussis?

Accepted Answer

90%

Answer

80%

Answer

70%

Answer

50%

Question 7

According to the WHO-recommended Expanded Program on Immunization (EPI) Cluster sampling methodology for assessing primary immunization coverage, what is the age group of children surveyed?

Accepted Answer

12-23 months

Answer

0-12 months

Answer

6-12 months

Answer

9-12 months

Question 8

BCG vaccination is administered by which route?

Accepted Answer

Intradermal

Answer

Subcutaneous

Answer

Intramuscular

Answer

Subdermal

Question 9

Both active and passive immunization is given in all of the following conditions, EXCEPT:

Accepted Answer

Measles

Answer

Tetanus

Answer

Rabies

Answer

HBV

Question 10

Which vaccine is used for the prevention of Japanese Encephalitis?

Accepted Answer

JEV vaccine

Answer

Dengvaxia

Answer

BCG vaccine

Answer

Hepatitis B vaccine

Immunization and Vaccine-Preventable Diseases — MCQs

Immunization and Vaccine-Preventable Diseases — MCQs

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