Immunization and Vaccine-Preventable Diseases Practice Questions

Q: What is the ideal recommended time for observation following immunization for adverse events following immunization (AEFI)?

30 minutes. **Explanation:** The correct answer is **30 minutes (Option B)**. **1. Why it is correct:** The primary purpose of post-vaccination observation is the early detection and management of immediate **anaphylactic reactions**. Anaphylaxis is a life-threatening, Type-I hypersensitivity reaction that typically occurs within minutes of exposure to an allergen. According to the **Universal Immunization Programme (UIP)** and **WHO guidelines**, every vaccine recipient must be observed for at least 30 minutes at the session site. This "waiting period" ensures that if a severe allergic reaction occurs, trained healthcare personnel can intervene immediately with Adrenaline (1:1000). **2. Why other options are incorrect:** * **15 minutes (Option A):** While some mild reactions occur early, 15 minutes is insufficient to capture the majority of immediate-onset anaphylactic events. * **45 minutes & 1 hour (Options C & D):** While longer observation is safer, it is logistically impractical for mass immunization campaigns and routine clinics. 30 minutes is the established gold standard that balances safety with public health efficiency. **3. High-Yield Clinical Pearls for NEET-PG:** * **Drug of Choice for Anaphylaxis:** Adrenaline (Epinephrine) 1:1000 concentration, administered **Intramuscularly (IM)** in the anterolateral aspect of the thigh. * **AEFI Surveillance:** AEFI is defined as any untoward medical occurrence following immunization, which does not necessarily have a causal relationship with the vaccine. * **Cold Chain:** Most UIP vaccines are stored between **+2°C to +8°C**. * **Most Heat Sensitive Vaccine:** Oral Polio Vaccine (OPV). * **Most Freeze Sensitive Vaccine:** Hepatitis B and DPT/Pentavalent.

Q: Thrombocytopenia is an adverse reaction of which vaccine?

MMR. **Explanation:** The correct answer is **MMR (Measles, Mumps, and Rubella)**. **Why MMR is the correct answer:** Immune Thrombocytopenic Purpura (ITP) is a recognized, though rare, adverse event following immunization (AEFI) specifically associated with the **Measles** component of the MMR vaccine. The underlying mechanism is believed to be **molecular mimicry**, where vaccine-induced antibodies cross-react with surface antigens on the patient’s platelets, leading to their destruction in the spleen. This typically occurs within 6 weeks of vaccination and is usually self-limiting. **Why other options are incorrect:** * **BCG:** Common adverse effects include local lymphadenitis and cold abscesses. It is not associated with platelet disorders. * **DPT:** Known for local reactions (pain, swelling) and systemic reactions like fever or persistent crying. The Pertussis component is rarely linked to encephalopathy, but not thrombocytopenia. * **Hep B:** The most significant (though rare) serious adverse effect is anaphylaxis. It is also occasionally linked to hypersensitivity reactions, but thrombocytopenia is not a characteristic feature. **High-Yield Clinical Pearls for NEET-PG:** * **Risk Ratio:** The risk of thrombocytopenia after MMR vaccination is approximately 1 in 30,000 doses—significantly lower than the risk of thrombocytopenia following a natural Measles or Rubella infection. * **Other MMR Side Effects:** Febrile seizures (due to the Measles component) and transient arthralgia (due to the Rubella component). * **Contraindication:** MMR is a **Live Attenuated Vaccine** and is contraindicated in pregnancy and severely immunocompromised individuals. * **Storage:** MMR is highly heat-sensitive and must be stored at +2°C to +8°C, protected from light.

Q: Post exposure, Measles vaccine must be given within how many days?

3-4 days. **Explanation:** The correct answer is **A. 3-4 days**. **1. Why 3-4 days is correct:** Measles has an incubation period of approximately 10–14 days. When a susceptible individual is exposed to the virus, the Measles vaccine can provide **post-exposure prophylaxis (PEP)** if administered within **72 hours (3 days)** of exposure. Some guidelines extend this window up to 4 days. The vaccine induces an immune response faster than the natural progression of the virus, effectively preventing or significantly modifying the severity of the disease. **2. Why the other options are incorrect:** * **B & C (10–14 days):** This is the typical **incubation period** of Measles. By this time, the virus has already replicated extensively, and clinical symptoms (prodrome/rash) begin to appear. Vaccination at this stage is ineffective as PEP. * **D (1-6 months):** This timeframe is irrelevant for PEP. However, it is worth noting that **Human Normal Immunoglobulin (Ig)** can be given up to 6 days post-exposure for those who cannot receive the live vaccine (e.g., infants <6 months or pregnant women). **3. High-Yield Clinical Pearls for NEET-PG:** * **Vaccine vs. Immunoglobulin:** If the 72-hour window for the vaccine is missed, Immunoglobulin can be administered within **6 days** of exposure to prevent or attenuate the disease. * **Minimum Age for PEP:** The Measles vaccine can be given as PEP to infants as young as **6 months**. However, this "zero dose" does not count toward the routine schedule; they must still receive the scheduled doses at 9 and 15 months. * **Type of Vaccine:** Measles is a **Live Attenuated Vaccine** (Edmonston-Zagreb strain in India). * **Infectivity:** Measles is most infectious during the **prodromal stage** (4 days before to 4 days after the appearance of the rash).

Q: The Vi polysaccharide vaccine for typhoid is administered by which route?

Intramuscular. ### Explanation The **Vi polysaccharide vaccine** (e.g., Typhim VI) is a subunit vaccine containing the purified capsular polysaccharide antigen of *Salmonella typhi*. It is administered as a **single-dose intramuscular (IM)** injection, usually into the deltoid muscle. It provides protection by inducing IgG antibodies against the Vi antigen. **Analysis of Options:** * **B. Intramuscular (Correct):** This is the standard route for the Vi polysaccharide vaccine. It is approved for use in individuals aged 2 years and older. * **A. Oral:** This route is used for the **Ty21a vaccine**, which is a live-attenuated liquid or capsule formulation. It requires a schedule of three to four doses on alternate days. * **C. Intravenous:** Vaccines are never administered intravenously as this bypasses the necessary immune processing by local APCs and increases the risk of systemic anaphylaxis. * **D. Intradermal:** While some vaccines (like BCG or Rabies) use this route, the Vi polysaccharide vaccine is specifically formulated for IM use to ensure optimal absorption and immunogenicity. **High-Yield Clinical Pearls for NEET-PG:** * **Age Limit:** Vi polysaccharide vaccine is not effective in children **<2 years** because their immune systems cannot mount a T-cell independent response to polysaccharides. * **Typhoid Conjugate Vaccine (TCV):** This is the preferred vaccine now (e.g., Typbar-TCV). By conjugating the Vi antigen to a protein carrier (Tetanus Toxoid), it becomes immunogenic for infants as young as **6 months** and provides longer-lasting immunity. * **Revaccination:** For the Vi polysaccharide vaccine, a booster dose is recommended every **3 years** for those at continued risk. * **Efficacy:** Both Vi polysaccharide and Ty21a provide approximately 50-80% protection.

Q: Meningococcal vaccine is available for all of the following serogroups, except?

Group B. **Explanation:** The correct answer is **Group B**. The primary challenge in developing a vaccine against **Serogroup B** *Neisseria meningitidis* lies in its capsular polysaccharide structure. Unlike other serogroups, the Group B capsule contains **polysialic acid**, which is structurally identical to the neural cell adhesion molecules (NCAMs) found in human fetal and adult brain tissues. Because of this molecular mimicry, the human immune system recognizes the Group B capsule as "self," making it poorly immunogenic and posing a theoretical risk of autoimmunity if used in a traditional polysaccharide vaccine. **Analysis of Options:** * **Group A, C, Y, and W-135:** These serogroups have distinct capsular polysaccharides that are highly immunogenic. They are included in both the **Quadrivalent Polysaccharide Vaccine** and the **Quadrivalent Conjugate Vaccine** (e.g., MenACWY). These are standard for travelers (Haj pilgrims) and high-risk individuals. * **Group B:** While a "protein-based" vaccine (using recombinant proteins rather than capsular polysaccharides, such as Bexsero or Trumenba) has been developed recently in some countries, it is **not** part of the standard polysaccharide or conjugate vaccines used globally and in India. In the context of standard NEET-PG questions regarding capsular vaccines, Group B is the classic "except." **High-Yield Clinical Pearls for NEET-PG:** 1. **Haj Pilgrims:** Vaccination with the Quadrivalent (A, C, Y, W-135) vaccine is mandatory for pilgrims traveling to Saudi Arabia. 2. **Chemoprophylaxis:** Rifampicin is the drug of choice for close contacts; Ciprofloxacin or Ceftriaxone are alternatives. 3. **Vaccine Type:** Polysaccharide vaccines are ineffective in children <2 years; Conjugate vaccines are preferred for long-term immunity and herd protection.

Q: Regarding the Hepatitis A vaccine schedule, which of the following is true for all EXCEPT?

Recommended only in immunocompromised children. **Explanation:** The Hepatitis A vaccine is recommended for **all children** as part of universal immunization or catch-up vaccination, not just for those who are immunocompromised. In fact, while the killed vaccine is safe for immunocompromised individuals, the **live attenuated vaccine is generally contraindicated** in this group. Therefore, Option D is the "except" statement and the correct answer. **Analysis of Options:** * **Option A:** The first dose of the Hepatitis A vaccine is typically administered at **12 months of age** (range 12–23 months) to ensure the disappearance of maternal antibodies, which could interfere with the immune response. * **Option B:** The **Inactivated (Killed) Vaccine** (e.g., Havrix) requires a **two-dose schedule**, usually given at a 6-month interval (0 and 6 months). It provides long-term immunity. * **Option C:** The **Live Attenuated Vaccine** (e.g., H2 strain) is unique because it is highly immunogenic and requires only a **single dose** to provide adequate protection, making it a cost-effective option in many settings. **High-Yield Clinical Pearls for NEET-PG:** * **Route:** Both live and killed vaccines are administered **Intramuscularly (IM)** in the anterolateral thigh or deltoid. * **Post-exposure Prophylaxis (PEP):** Hepatitis A vaccine can be used for PEP if given within **14 days** of exposure in healthy individuals aged 1–40 years. * **Epidemiology:** Hepatitis A is the most common cause of acute viral hepatitis in children in India. * **Contraindication:** Do not give the live vaccine to pregnant women or severely immunocompromised patients.

Q: A one-year-old child presents for vaccination. What vaccine(s) should be administered?

Measles, DPT, OPV, Hib, Hepatitis B. **Explanation:** The core concept behind this question is the **National Immunization Schedule (NIS)** of India, specifically focusing on the transition from infancy to the second year of life. **Why Option B is Correct:** At **9 completed months**, the primary series of vaccinations includes the **1st dose of Measles (now MR)** and the **Vitamin A** supplement. However, the question specifies a **one-year-old child**. According to the NIS, if a child has missed their primary doses or is presenting for their scheduled boosters/catch-up, they are eligible for: 1. **Measles (MR):** 1st dose (if missed at 9 months) or preparing for the 2nd dose (16–24 months). 2. **DPT, OPV, Hib, and Hepatitis B:** These are part of the **Pentavalent** series (DPT+HepB+Hib) and the primary OPV series. Under catch-up immunization guidelines, a child presenting at one year should be ensured protection against all these antigens. **Analysis of Incorrect Options:** * **Option A:** BCG, OPV, and Hep B are "at-birth" doses. While BCG can be given up to one year, this option lacks the critical Measles and DPT components required for a one-year-old. * **Options C & D:** These options omit **Measles**, which is the most crucial vaccine introduced at the 9-month mark. Measles remains a leading cause of vaccine-preventable mortality in children under five. **High-Yield NEET-PG Pearls:** * **BCG:** Can be given up to **1 year** of age. If given after 1 month, the dose is 0.1 ml (instead of 0.05 ml). * **Vitamin A:** 1st dose (1 lakh IU) is given at 9 months with MR; subsequent doses (2 lakh IU) are given every 6 months up to 5 years (Total 9 doses/17 lakh IU). * **Pentavalent Vaccine:** Replaced individual DPT and Hep B doses in the primary schedule (6, 10, 14 weeks) to reduce the number of pricks. * **JE Vaccine:** In endemic districts, the 1st dose is administered at 9 months and the 2nd dose at 16–24 months.

Question 1

What is true about the varicella vaccine?

Accepted Answer

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

Answer

It is poorly immunogenic.

Answer

Its immunity lasts for 4-6 months.

Answer

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

Question 2

What is the ideal recommended time for observation following immunization for adverse events following immunization (AEFI)?

Accepted Answer

30 minutes

Answer

15 minutes

Answer

45 minutes

Answer

1 hour

Question 3

Which of the following vaccines is not given to an unimmunized 8-year-old male child?

Accepted Answer

Acellular pertussis vaccine

Answer

Inactivated polio vaccine

Answer

Hepatitis B vaccine

Answer

Measles vaccine

Question 4

Thrombocytopenia is an adverse reaction of which vaccine?

Accepted Answer

MMR

Answer

BCG

Answer

DPT

Answer

Hep B

Question 5

Post exposure, Measles vaccine must be given within how many days?

Accepted Answer

3-4 days

Answer

10 days

Answer

10-14 days

Answer

1-6 months

Question 6

The Vi polysaccharide vaccine for typhoid is administered by which route?

Accepted Answer

Intramuscular

Answer

Oral

Answer

Intravenous

Answer

Intradermal

Question 7

Meningococcal vaccine is available for all of the following serogroups, except?

Accepted Answer

Group B

Answer

Group A

Answer

Group C

Answer

Group Y

Question 8

Which of the following statements regarding tetanus is true?

Accepted Answer

Tetanus toxoid and tetanus immunoglobulin may both be administered in suspected tetanus cases.

Answer

A five-dose immunization provides lifelong immunity.

Answer

Tetanus toxoid provides no protection in the current injury.

Answer

Tetanus toxoid is useless once 12 hours have passed following injury.

Question 9

Regarding the Hepatitis A vaccine schedule, which of the following is true for all EXCEPT?

Accepted Answer

Recommended only in immunocompromised children

Answer

Recommended at 12 months of age

Answer

Two doses of killed vaccine given 6 months apart

Answer

One dose of live vaccine

Question 10

A one-year-old child presents for vaccination. What vaccine(s) should be administered?

Accepted Answer

Measles, DPT, OPV, Hib, Hepatitis B

Answer

BCG, OPV, Hepatitis B

Answer

DPT, OPV, Hib, Hepatitis B

Answer

DPT, OPV, Hepatitis B

Immunization and Vaccine-Preventable Diseases — MCQs

Immunization and Vaccine-Preventable Diseases — MCQs

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