Immunization and Vaccine-Preventable Diseases Practice Questions

Q: What is the recommended dose of Rabies immunoglobulin?

20 IU/kg body weight. **Explanation:** The correct answer is **C. 20 IU/kg body weight**. **1. Why the correct answer is right:** Rabies Immunoglobulin (RIG) provides immediate **passive immunity** by neutralizing the rabies virus at the wound site before the patient’s own immune system can produce antibodies via vaccination (active immunity). The standard dose for **Human Rabies Immunoglobulin (HRIG)** is **20 IU/kg body weight**. It is administered as a one-time dose, ideally on Day 0, by infiltrating as much as possible into and around the wound(s). **2. Why the incorrect options are wrong:** * **A & B (10-15 IU/kg):** These doses are sub-therapeutic and would not provide sufficient neutralizing antibodies to prevent the virus from entering the peripheral nerves. * **D (25 IU/kg):** This exceeds the standard HRIG dose. However, it is important to note that if **Equine Rabies Immunoglobulin (ERIG)** is used instead of HRIG, the dose is **40 IU/kg body weight** (double the HRIG dose) due to its lower potency and faster clearance. **3. High-Yield Clinical Pearls for NEET-PG:** * **Site of Injection:** RIG should be infiltrated **locally** into the wound. Any remaining volume should be injected intramuscularly at a site distant from the vaccine injection. * **Timing:** RIG is indicated for **Category III bites** (and Category II in immunocompromised patients). It can be given up to **7 days** after the first dose of the vaccine; beyond 7 days, it is not recommended as the body starts producing its own antibodies. * **Never exceed the dose:** Excessive RIG can interfere with the active immune response generated by the rabies vaccine. * **No RIG for previously immunized:** If a patient has a documented history of complete Pre-exposure or Post-exposure prophylaxis, RIG is **not** required during re-exposure.

Q: Which of the following vaccines has maximum efficacy after a single dose?

Measles. **Explanation:** The efficacy of a vaccine refers to the percentage reduction in disease incidence among vaccinated persons compared to unvaccinated ones. **Why Measles is the Correct Answer:** Measles is a **Live Attenuated Vaccine**. Live vaccines generally mimic a natural infection, leading to robust humoral and cell-mediated immunity. A single dose of the Measles vaccine (given at 9 months in India) has an exceptionally high seroconversion rate of approximately **85–95%**. Because it is highly immunogenic, a single dose is sufficient to provide long-lasting protection in the majority of the population, making its single-dose efficacy superior to the other options listed. **Analysis of Incorrect Options:** * **Tetanus Toxoid (TT) & DPT:** These are **Toxoid/Killed vaccines**. Inactivated vaccines are generally less immunogenic than live vaccines. They require a primary series (multiple doses) followed by periodic boosters to achieve and maintain protective antibody titers. A single dose of TT or DPT provides negligible long-term protection. * **Typhoid:** Whether using the polysaccharide (Vi) or the conjugate vaccine, the efficacy of a single dose is lower (approx. 60–70% for Vi) compared to Measles, and the immunity tends to wane over 2–3 years, requiring revaccination. **High-Yield Clinical Pearls for NEET-PG:** * **Maximum Efficacy:** Measles (~95%) > BCG (0–80%, highly variable). * **Cold Chain:** Measles vaccine is highly heat-sensitive and must be reconstituted only with the provided diluent. Once reconstituted, it must be used within **4 hours**. * **Zero Dose:** In the context of Polio, the "Zero Dose" refers to the dose given at birth to induce local intestinal immunity. * **Most Heat Sensitive Vaccine:** Oral Polio Vaccine (OPV). * **Most Heat Resistant Vaccine:** Tetanus Toxoid (TT).

Q: What is the standard schedule for administering the Rabies vaccine?

0, 3, 7, 14, 28 days. The standard schedule for **Post-Exposure Prophylaxis (PEP)** using Modern Cell Culture Vaccines (MCCV) via the intramuscular (IM) route is the **Essen Protocol**, which follows the **0, 3, 7, 14, and 28-day** regimen. ### 1. Why Option B is Correct The goal of PEP is to induce active immunity before the rabies virus reaches the central nervous system. The 5-dose IM schedule (administered in the deltoid muscle) ensures optimal antibody titers. * **Day 0:** First dose (as soon as possible after exposure). * **Days 3, 7:** Early doses to prime the immune system. * **Days 14, 28:** Late doses to ensure long-lasting protective antibody levels (seroconversion >0.5 IU/mL). ### 2. Why Other Options are Incorrect * **Option A:** Identical to B (Correct). * **Options C & D:** These schedules do not align with WHO or National Guidelines for post-exposure treatment. A 0, 7, 21 (or 28) day schedule is typically used for **Pre-Exposure Prophylaxis (PrEP)** in high-risk individuals, not for post-exposure management. ### 3. NEET-PG High-Yield Clinical Pearls * **Intradermal (ID) Regimen:** The updated **Thai Red Cross Schedule** (Updated TRC-ID) is **2-2-2-0-2** (2 doses on days 0, 3, 7, and 28). Note that the Day 14 dose is skipped in the ID regimen. * **Site of Injection:** Always **Deltoid** in adults and **Anterolateral thigh** in children. **Never** give rabies vaccine in the gluteal region (fat interferes with absorption). * **Re-exposure:** If a previously immunized person is bitten again, only two booster doses are needed on **Days 0 and 3** (no Rabies Immunoglobulin required). * **Category III Bites:** Always require both Vaccine + Rabies Immunoglobulin (RIG) infiltrated into the wound.

Q: How often are booster doses recommended for the ViPS vaccine?

Every 3 years. **Explanation:** The **ViPS (Vi Polysaccharide) vaccine** is a parenteral (injectable) subunit vaccine used for protection against Typhoid fever. It contains the purified Vi capsular polysaccharide antigen of *Salmonella typhi*. **1. Why Option C is Correct:** The ViPS vaccine is T-cell independent. Because it is a pure polysaccharide vaccine, it does not induce immunological memory. Antibody levels (specifically IgG) elicited by the vaccine decline significantly over time, and the protective efficacy drops below threshold levels after a few years. Therefore, to maintain protective immunity, a **booster dose is required every 3 years**. It is recommended for individuals aged 2 years and older. **2. Why Other Options are Incorrect:** * **Option A (Every year):** Annual boosters are unnecessary as the protective antibody levels generally persist for at least 2–3 years. * **Option B (Every 2 years):** While some older guidelines suggested frequent dosing, the standard WHO and National guidelines for ViPS specify a 3-year interval. * **Option D (Every 4 years):** By the fourth year, the efficacy of the polysaccharide vaccine significantly wanes, leaving the individual susceptible to infection. **3. High-Yield Clinical Pearls for NEET-PG:** * **Typhoid Conjugate Vaccine (TCV):** Unlike ViPS, TCV (e.g., Typbar-TCV) is conjugated to a protein carrier (Tetanus Toxoid). This makes it T-cell dependent, providing longer-lasting immunity, and it can be given as early as **6 months of age**. * **Oral Ty21a Vaccine:** A live attenuated vaccine given in a 3-dose schedule (Days 1, 3, and 5). It requires a booster every **3 to 5 years**. * **Minimum Age:** ViPS cannot be given to children **under 2 years** because their immune systems do not respond well to polysaccharide antigens.

Q: Which of the following vaccines is routinely administered during pregnancy?

Tetanus toxoid vaccine. **Explanation:** The administration of vaccines during pregnancy aims to protect both the mother and the newborn through the transplacental transfer of maternal antibodies. **Correct Option: C. Tetanus toxoid vaccine** Under the Universal Immunization Programme (UIP) in India, Tetanus and adult Diphtheria (Td) vaccine is routinely administered to all pregnant women. The primary goal is to prevent **Maternal and Neonatal Tetanus (MNT)**. The schedule involves two doses (Td-1 as early as possible and Td-2 after 4 weeks) or a single booster dose if the woman was immunized within the last 3 years. **Analysis of Incorrect Options:** * **A. Influenza vaccine:** While recommended by some global bodies (like the CDC) to prevent complications, it is not part of the **routine** national immunization schedule for all pregnant women in India unless specific risk factors are present. * **B. Oral polio vaccine (OPV):** OPV is a **Live Attenuated Vaccine**. Live vaccines are generally contraindicated during pregnancy due to the theoretical risk of viral transmission to the fetus. * **D. Rabies vaccine:** This is a post-exposure prophylaxis vaccine. It is administered during pregnancy only if a woman is bitten by a suspected rabid animal. It is not a "routine" antenatal vaccine. **High-Yield NEET-PG Pearls:** * **Live Vaccines Contraindicated:** BCG, MMR, Varicella, and Yellow Fever (unless high risk). * **Safe Vaccines:** All inactivated/killed vaccines and toxoids (Td, Hepatitis B, Inactivated Influenza) are generally safe. * **Td vs TT:** The UIP has replaced Tetanus Toxoid (TT) with **Td (Tetanus and adult Diphtheria)** to provide additional protection against diphtheria. * **Ideal Timing for Tdap:** In some private sectors, a single dose of Tdap (Tetanus, diphtheria, and acellular pertussis) is preferred between 27–36 weeks of gestation to protect the infant from Pertussis.

Q: What is the total dose of Vitamin A given under the National Immunisation Schedule?

1.7 million IU. The correct answer is **1.7 million IU (Option B)**. ### **Explanation** Under the Universal Immunization Programme (UIP) in India, Vitamin A supplementation is administered to children between **9 months and 5 years** of age to prevent nutritional blindness and reduce child mortality. The total dosage is calculated based on a schedule of **9 doses**: 1. **1st Dose:** Given at 9 months (with Measles/MR vaccine) = **1 lakh IU** (1 ml). 2. **2nd Dose:** Given at 18 months (with MR 2nd dose/DPT booster) = **2 lakh IU** (2 ml). 3. **3rd to 9th Doses:** Administered every 6 months until the age of 5 years. There are 7 such doses, each of **2 lakh IU**. * Calculation: 1 lakh + (8 doses × 2 lakh) = 1 + 16 = **17 lakh IU (1.7 million IU).** ### **Why Other Options are Incorrect** * **Option A (1.6 million IU):** This is a common calculation error if the student forgets to include the first dose given at 9 months. * **Option C (1.8 million IU):** This would imply an extra dose or that the first dose was also 2 lakh IU, which is incorrect. * **Option D (2.0 million IU):** This does not align with the current 9-dose schedule under the National Immunization Schedule. ### **High-Yield Clinical Pearls for NEET-PG** * **Target Age Group:** 9 months to 5 years (Total 9 doses). * **Concentration:** The Vitamin A syrup bottle usually contains 1 lakh IU per ml. * **Minimum Interval:** There must be a minimum gap of **6 months** between two consecutive doses. * **Treatment of Xerophthalmia:** The schedule is different (Day 0, Day 1, and Day 14) with age-specific dosing (1 lakh IU for 1 year). * **Public Health Impact:** Vitamin A supplementation reduces all-cause mortality in children by approximately 23-24%.

Q: Which of the following vaccines, if contaminated, can cause Toxic Shock Syndrome (TSS)?

Measles vaccine. **Explanation:** **Toxic Shock Syndrome (TSS)** in the context of immunization is a severe, life-threatening complication caused by the contamination of multi-dose vaccine vials with **Staphylococcus aureus**. **Why Measles Vaccine is the Correct Answer:** The Measles vaccine is a **live-attenuated, lyophilized (freeze-dried)** vaccine that requires reconstitution with a diluent. Once reconstituted, the vaccine does not contain any preservative (like thiomersal). If the reconstituted vial is kept at room temperature for more than a few hours (usually >4–6 hours), it becomes an ideal culture medium for *Staphylococcus aureus*. If contaminated, the bacteria produce exotoxins that lead to rapid-onset high fever, vomiting, diarrhea, and circulatory collapse (TSS) in vaccinated children. This is why the Universal Immunization Program (UIP) strictly mandates discarding reconstituted measles/MR vaccines after 4 hours. **Analysis of Incorrect Options:** * **B. DPT:** This is a liquid vaccine that contains **Thiomersal** as a preservative, which inhibits bacterial growth, making TSS highly unlikely. * **C. Hepatitis B:** Like DPT, this is a liquid-form vaccine containing preservatives. * **D. Typhoral:** This is an oral live-attenuated vaccine (Ty21a) administered in capsule form; it does not involve reconstitution or the risk of parenteral staphylococcal contamination. **High-Yield Clinical Pearls for NEET-PG:** * **The "4-Hour Rule":** Reconstituted vaccines (Measles, BCG, JE) must be discarded after 4 hours or at the end of the session, whichever is earlier. * **Most Common Organism:** *Staphylococcus aureus* is the most common cause of vaccine-associated TSS. * **Open Vial Policy:** Note that the WHO Open Vial Policy applies to multi-dose liquid vaccines (DPT, HepB, OPV, TT) but **does not** apply to reconstituted vaccines (Measles, BCG, JE). These must be discarded.

Question 1

Which of the following Oral Polio Vaccine (OPV) types are currently usable?

Accepted Answer

Only OPV Types 1 and 2

Answer

Only OPV Type 1

Answer

Only OPV Types 1, 2, and 3

Answer

Only OPV Types 3 and 4

Question 2

What is the recommended dose of Rabies immunoglobulin?

Accepted Answer

20 IU/kg body weight

Answer

10 IU/Kg body weight

Answer

15 IU/kg body weight

Answer

25 IU/kg body weight

Question 3

Which of the following is true about the varicella vaccine?

Accepted Answer

Salicylates should be avoided for 4-6 weeks after vaccination.

Answer

It is poorly immunogenic.

Answer

The immunity lasts for 4-6 months.

Answer

It is given to children less than 12 months of age if they do not have chickenpox.

Question 4

Which of the following vaccines has maximum efficacy after a single dose?

Accepted Answer

Measles

Answer

Tetanus toxoid

Answer

DPT

Answer

Typhoid

Question 5

What is the standard schedule for administering the Rabies vaccine?

Accepted Answer

0, 3, 7, 14, 28 days

Answer

0, 7, 21, 60 days

Answer

0, 7, 21, 30 days

Question 6

How often are booster doses recommended for the ViPS vaccine?

Accepted Answer

Every 3 years

Answer

Every year

Answer

Every 2 years

Answer

Every 4 years

Question 7

Which of the following vaccines is routinely administered during pregnancy?

Accepted Answer

Tetanus toxoid vaccine

Answer

Influenza vaccine

Answer

Oral polio vaccine

Answer

Rabies vaccine

Question 8

The protective value of a vaccine is stated as 95%. What does this mean?

Accepted Answer

There is a 5% probability of infection among those who have been vaccinated.

Answer

All individuals who receive the vaccine are completely protected.

Answer

Among the vaccinated population, 95% are immune to the disease.

Answer

95% of vaccinated individuals are protected from the disease, while 5% still contract it.

Question 9

What is the total dose of Vitamin A given under the National Immunisation Schedule?

Accepted Answer

1.7 million IU

Answer

1.6 million IU

Answer

1.8 million IU

Answer

2.0 million IU

Question 10

Which of the following vaccines, if contaminated, can cause Toxic Shock Syndrome (TSS)?

Accepted Answer

Measles vaccine

Answer

DPT

Answer

Hepatitis B

Answer

Typhoral

Immunization and Vaccine-Preventable Diseases — MCQs

Immunization and Vaccine-Preventable Diseases — MCQs

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