Immunization and Vaccine-Preventable Diseases — MCQs

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

Question 241: Which of the following is FALSE regarding pre-exposure tetanus immunization?

A. If already immunized, a booster in the last trimester is advocated.
B. The vaccine is given intramuscularly.
C. Tetanus immunoglobulin is injected to the mother. (Correct Answer)
D. Two doses are recommended.

Explanation: ### Explanation **1. Why Option C is the Correct Answer (The False Statement):** Pre-exposure tetanus immunization for pregnant women involves **active immunization** using Tetanus Toxoid (TT) or Tetanus-diphtheria (Td) vaccine, not passive immunization. **Tetanus Immunoglobulin (TIG)** provides immediate, short-term passive immunity and is reserved for post-exposure prophylaxis in unimmunized individuals with "tetanus-prone" wounds. It is not part of the routine antenatal immunization schedule. **2. Analysis of Incorrect Options (True Statements):** * **Option A:** If a woman was previously fully immunized (within the last 3-5 years), a single **booster dose** in the current pregnancy is sufficient to maintain protective antibody levels. * **Option B:** Tetanus vaccines (TT/Td) are adsorbed onto aluminum salts to enhance immunogenicity; therefore, they must be administered via the **intramuscular (IM)** route (usually in the deltoid) to prevent local irritation or sterile abscesses associated with subcutaneous injection. * **Option D:** For an unimmunized pregnant woman, **two doses** are recommended. The first dose is given as early as possible (ideally at 16-20 weeks), and the second dose is given 4 weeks later (at least 2 weeks before delivery) to ensure adequate placental transfer of IgG to the fetus. **3. NEET-PG High-Yield Pearls:** * **Current Protocol:** Under the Universal Immunization Programme (UIP), **Td (Tetanus & adult Diphtheria)** has replaced TT to provide additional protection against diphtheria. * **Protective Level:** A serum antitoxin level of **0.01 IU/ml** is considered the minimum protective threshold. * **Neonatal Tetanus:** Immunizing the mother prevents *Tetanus Neonatorum* by facilitating the transplacental passage of maternal IgG antibodies to the fetus. * **The "3-Year Rule":** If a woman has received 2 doses of TT/Td in a pregnancy followed by another pregnancy within 3 years, only one **booster dose** is required.

Question 242: Vaccine and immunoglobulin can be given together in all conditions except:

A. Tetanus
B. Rabies
C. Measles (Correct Answer)
D. HBV

Explanation: ### Explanation The core principle behind this question is the **interference between pre-formed antibodies (immunoglobulins) and live-attenuated vaccines.** **Why Measles is the correct answer:** Measles vaccine is a **live-attenuated vaccine**. If measles immunoglobulin is administered simultaneously with the vaccine, the pre-formed antibodies will neutralize the live virus particles before they can replicate sufficiently to trigger an active immune response. This renders the vaccine ineffective. According to standard guidelines, if immunoglobulin is given, one must wait at least **3 to 11 months** (depending on the dose) before administering the Measles/MMR vaccine. **Why the other options are incorrect:** In cases of **Tetanus, Rabies, and Hepatitis B (HBV)**, the goal is to provide **Passive-Active Immunity**. * **Rabies & Tetanus:** These are life-threatening conditions where immediate protection (Passive) is required via RIG/TIG, while the body simultaneously starts producing its own antibodies (Active) via the vaccine. * **HBV:** Post-exposure prophylaxis (e.g., needle-stick injury or birth to an HBsAg+ mother) requires both HBIG and the Hep B vaccine for immediate and long-term coverage. * **Key Rule:** In these cases, the vaccine and immunoglobulin must be administered at **different anatomical sites** using different syringes to prevent physical neutralization. **High-Yield Clinical Pearls for NEET-PG:** * **Live Vaccines vs. IG:** Always maintain a gap. If a live vaccine is given first, wait 2 weeks before giving IG. If IG is given first, wait at least 3 months before giving a live vaccine. * **Exception:** The **Yellow Fever** vaccine is generally not affected by IG. * **Oral Live Vaccines:** Oral Polio Vaccine (OPV) and Rotavirus are not affected by systemic IG and can be given simultaneously. * **Passive-Active Immunity** is the standard of care for post-exposure prophylaxis in Rabies, Tetanus, HBV, and Varicella.

Question 243: Side effects of the Pertussis vaccine include:

A. Local pain
B. Excessive cry
C. Fever
D. All of the above (Correct Answer)

Explanation: The **Pertussis vaccine**, typically administered as part of the DPT (Diphtheria, Pertussis, and Tetanus) combination, is known for being the most reactogenic component of the vaccine. This reactogenicity is primarily due to the whole-cell pertussis (*wP*) component, which contains numerous antigens and endotoxins. ### **Explanation of Options:** * **Local Pain (Option A):** This is the most common side effect, occurring in about 50% of recipients. It is characterized by redness, swelling, and tenderness at the injection site due to a localized inflammatory response. * **Excessive Cry (Option B):** Persistent, high-pitched, or inconsolable crying (lasting >3 hours) is a recognized systemic reaction to the pertussis antigen. It is often associated with irritability and malaise. * **Fever (Option C):** Mild to moderate fever is a frequent systemic reaction as the body initiates an immune response. Since all three symptoms are documented adverse effects following immunization (AEFI) with the pertussis vaccine, **Option D (All of the above)** is the correct answer. ### **High-Yield Clinical Pearls for NEET-PG:** * **Whole-cell (wP) vs. Acellular (aP):** The acellular pertussis vaccine (aP) has significantly fewer side effects but is generally considered to have a shorter duration of immunity compared to the whole-cell vaccine used in the National Immunization Schedule. * **Absolute Contraindications:** A history of **Encephalopathy** (e.g., coma, seizures) within 7 days of a previous dose is an absolute contraindication to further doses of the pertussis vaccine. * **Neurological Reactions:** While rare, the pertussis component is associated with febrile seizures and hypotonic-hyporesponsive episodes (HHE). * **Management:** If a child reacts severely to DPT, the pertussis component is omitted, and the schedule is completed using the **DT vaccine**.

Question 244: Which of the following is a serogroup included in the meningococcal vaccine?

A. ACWY (Correct Answer)
B. ABCW
C. CYW
D. ABCY

Explanation: ### Explanation **Correct Option: A (ACWY)** **Medical Concept:** *Neisseria meningitidis* is classified into serogroups based on the composition of its capsular polysaccharide. While there are 12 serogroups, most invasive meningococcal diseases globally are caused by six: **A, B, C, W-135, X, and Y**. The standard quadrivalent meningococcal vaccines (both Polysaccharide and Conjugate types) are designed to target the four most prevalent serogroups: **A, C, W-135, and Y**. These vaccines provide broad protection against epidemic and endemic meningitis in various geographical regions, including the "Meningitis Belt" of sub-Saharan Africa and during the Hajj pilgrimage. **Analysis of Incorrect Options:** * **Options B, C, and D:** These are incorrect combinations. While **Serogroup B** is a major cause of disease (especially in developed nations), it is traditionally excluded from the quadrivalent (ACWY) vaccine. This is because the Serogroup B polysaccharide is poorly immunogenic (it mimics human neural cell adhesion molecules). Protection against Serogroup B requires a separate, protein-based vaccine (e.g., Bexsero or Trumenba), rather than the standard polysaccharide/conjugate ACWY formulation. **High-Yield Clinical Pearls for NEET-PG:** * **Vaccine Types:** Available as **MPSV4** (Polysaccharide) and **MenACWY** (Conjugate). The conjugate vaccine is preferred due to longer-lasting immunity and herd protection. * **Hajj Requirement:** Proof of vaccination with the quadrivalent ACWY vaccine is a mandatory visa requirement for pilgrims traveling to Saudi Arabia. * **Target Population:** High-risk groups include individuals with terminal complement deficiency, functional or anatomic asplenia, and laboratory personnel. * **Serogroup A:** Historically the most common cause of epidemics in Africa and Asia.

Question 245: A 1-year-old child who received BCG at birth and OPV is due for vaccination. Which of the following vaccines should be administered?

A. BCG, OPV, Hepatitis B
B. Measles, DPT, OPV, Hib, Hepatitis B (Correct Answer)
C. DPT, OPV, Hib, Hepatitis B
D. DPT, OPV, Hepatitis B

Explanation: ### Explanation **1. Why Option B is Correct:** According to the **National Immunization Schedule (NIS)** in India, a child who has only received BCG and OPV at birth is significantly delayed. At 1 year of age, the child must receive the "catch-up" doses for all primary vaccines missed during the first year. * **Pentavalent Vaccine (DPT + Hib + Hep B):** The child needs protection against Diphtheria, Pertussis, Tetanus, *Haemophilus influenzae* type b, and Hepatitis B. * **OPV:** Subsequent doses of Oral Polio Vaccine are required to build mucosal immunity. * **Measles (MR):** The first dose is typically given at 9 completed months. Since the child is now 1 year old, this is a priority to prevent outbreaks. **2. Why Other Options are Incorrect:** * **Option A:** BCG is already administered at birth. Repeating it is unnecessary unless there is no scar and the child is <1 year (though current guidelines focus on birth dose). It misses DPT and Measles. * **Option C & D:** These options omit **Measles**, which is a critical vaccine administered at 9 months. Failure to include Measles leaves the child vulnerable to one of the most common causes of vaccine-preventable childhood mortality. **3. NEET-PG High-Yield Pearls:** * **Pentavalent Vaccine:** Replaces individual DPT, Hep B, and Hib shots. It is given at 6, 10, and 14 weeks. * **Measles/MR Vaccine:** Minimum age is 9 months. If missed, it can be given up to 5 years of age. * **BCG:** Can be given up to 1 year of age if missed at birth. * **Vitamin A:** The first dose (1 lakh IU) is always administered alongside the 1st dose of Measles/MR. * **Catch-up Rule:** For a "left-out" child, always prioritize the primary series (DPT, OPV, Hep B, Measles) to ensure basic immunity.

Question 246: Which of the following statements about typhoid vaccines is incorrect?

A. The Vi polysaccharide vaccine is given in a single dose.
B. The recommended storage temperature is +2 to +8°C.
C. The Typherix vaccine is administered in three doses.
D. Typherix vaccine cannot be given concurrently with other live vaccines. (Correct Answer)

Explanation: ### Explanation **1. Why Option D is the Correct (Incorrect Statement):** Typherix is a **Vi polysaccharide (inactivated/subunit)** vaccine, not a live vaccine. According to standard immunization principles, inactivated vaccines can be administered simultaneously with other vaccines (live or inactivated) at different injection sites without interfering with the immune response. Therefore, the statement that it *cannot* be given concurrently with live vaccines is medically incorrect. **2. Analysis of Other Options:** * **Option A:** The Vi polysaccharide vaccine (e.g., Typhim Vi, Typherix) is indeed administered as a **single 0.5 ml intramuscular dose**, providing protection for approximately 3 years. * **Option B:** Like most non-freeze-sensitive vaccines in the Universal Immunization Programme, typhoid vaccines must be stored in the cold chain at **+2 to +8°C**. Freezing should be avoided as it can damage the antigen. * **Option C:** This option is technically a distractor in some contexts, but in the context of this MCQ, Typherix (the Vi polysaccharide) is a single dose. However, if the question refers to the **Ty21a (Oral)** vaccine, that requires 3 doses (on days 1, 3, and 5). *Note: In many PG exams, "Typherix" is used interchangeably with the Vi injectable class, which is single-dose.* **3. High-Yield Clinical Pearls for NEET-PG:** * **Ty21a (Oral Vaccine):** A live attenuated vaccine. Schedule: 3 doses (alternate days). Contraindicated in pregnancy and HIV. Must be taken on an empty stomach with cold liquid. * **Vi Polysaccharide (Injectable):** Given at age >2 years. Not effective in children <2 years due to poor T-cell independent immune response. * **Typhoid Conjugate Vaccine (TCG):** The newest "gold standard" (e.g., Typbar-TCV). It is conjugated to a tetanus toxoid carrier, making it immunogenic for infants as young as **6 months** and providing longer-lasting immunity. * **Efficacy:** TCV (>90%) > Vi Polysaccharide (approx. 70%) > Ty21a (approx. 50-60%).

Question 247: Which one of the following doses in Loeffler units of Diphtheria Toxoid is incorporated in DPT vaccine per dose?

A. 5
B. 15
C. 25 (Correct Answer)
D. 35

Explanation: ### Explanation **1. Why Option C (25) is Correct:** The DPT (Diphtheria, Pertussis, and Tetanus) vaccine is a combination vaccine used in the Universal Immunization Programme (UIP). According to the Indian Pharmacopoeia and WHO standards, each **0.5 ml dose** of the adsorbed DPT vaccine contains: * **Diphtheria Toxoid:** 20 to 30 Lf (Loeffler units or Limit of Flocculation). The standard accepted value for competitive exams is **25 Lf**. * **Tetanus Toxoid:** 5 to 25 Lf (usually 5–10 Lf). * **B. pertussis:** ≥ 4 IU (International Units). The Lf unit measures the quantity of the toxoid based on its ability to flocculate with a specific antitoxin. 25 Lf provides the optimal balance between inducing a robust immune response and minimizing local adverse reactions. **2. Why Other Options are Incorrect:** * **Option A (5):** This is too low for the primary DPT series. However, 2–5 Lf is the dose used in the **dT (adult-type)** vaccine to reduce the risk of hypersensitivity reactions in older children and adults. * **Option B (15):** This is an intermediate value not standard for the pediatric DPT formulation. * **Option D (35):** This exceeds the standard concentration, which would significantly increase the risk of local reactions (pain, swelling, and sterile abscesses) without providing additional clinical benefit. **3. High-Yield Clinical Pearls for NEET-PG:** * **Adjuvant:** Aluminum phosphate or hydroxide is used to enhance the immunogenicity of the toxoids. * **Storage:** DPT must be stored at **+2°C to +8°C**. It should **never be frozen** (Shake Test is used to check if it was previously frozen). * **Site of Injection:** Anterolateral aspect of the mid-thigh (Intramuscular). * **Contraindication:** A history of encephalopathy within 7 days of a previous dose is an absolute contraindication for the Pertussis component.

Question 248: Which age group is targeted in the WHO's catch-up vaccination strategy for measles elimination?

A. 6 months to 5 years
B. 9 months to 10 years
C. 9 months to 14 years (Correct Answer)
D. 6 months to 10 years

Explanation: ### Explanation **Correct Answer: C. 9 months to 14 years** The WHO’s global strategy for measles elimination involves a four-pronged approach: high routine coverage, a "second opportunity" for vaccination, effective surveillance, and **Catch-up campaigns**. The **Catch-up vaccination strategy** is a one-time nationwide campaign targeting all children in a broad age group, regardless of their previous vaccination or disease history. The goal is to rapidly interrupt measles virus transmission by closing immunity gaps in the population. The WHO specifically recommends the age group of **9 months to 14 years** for these campaigns because this cohort represents the primary reservoir for transmission in endemic or transitioning regions. **Analysis of Incorrect Options:** * **A & D (6 months):** Routine measles vaccination (MCV1) is generally not given before 9 months because maternal antibodies can interfere with the immune response, leading to vaccine failure. 6 months is only considered during outbreaks or for displaced populations. * **B (9 months to 10 years):** While many older strategies focused on younger children, the current elimination goal requires a wider net (up to 14 years) to ensure "herd immunity" levels (>95%) are reached across the entire pediatric and adolescent population. **High-Yield Clinical Pearls for NEET-PG:** * **Follow-up Campaigns:** Conducted every 2–4 years targeting children born since the last campaign (usually **9 months to 5 years**). * **Keep-up:** Refers to maintaining >95% coverage in routine immunization (MCV1 at 9 months and MCV2 at 16–24 months). * **Vitamin A:** Administered during measles treatment to reduce mortality (1 lakh IU for <6 months; 2 lakh IU for >1 year). * **Measles Elimination:** Defined as the absence of endemic measles transmission in a region for ≥12 months.

Question 249: Which vaccine need NOT be given to boys?

A. Mumps
B. German measles (Rubella) (Correct Answer)
C. Measles (Rubeola)
D. Small pox

Explanation: **Explanation:** The primary objective of the **Rubella (German Measles)** vaccine is not just to prevent the clinical disease, which is typically mild in children, but to prevent **Congenital Rubella Syndrome (CRS)**. CRS occurs when a pregnant woman is infected, leading to severe fetal complications like cataracts, deafness, and cardiac defects. Historically, in some public health strategies (such as the UK's initial policy), the vaccine was targeted exclusively at adolescent girls to ensure immunity before they reached childbearing age. While modern programs (like India’s MR/MMR campaign) follow a "mass approach" to eliminate the virus from the community, the specific medical rationale for excluding boys in certain selective strategies is that they do not pose a risk for CRS. **Analysis of Options:** * **Mumps (Option A):** Essential for boys because post-pubertal mumps infection can lead to **orchitis** and potential sterility. * **Measles (Option C):** A major cause of childhood morbidity and mortality (due to pneumonia and diarrhea) regardless of gender; it is a core component of the Universal Immunization Programme (UIP). * **Smallpox (Option D):** This vaccine is no longer given to anyone as the disease was declared eradicated by the WHO in 1980. However, historically, it was administered to both genders. **High-Yield Clinical Pearls for NEET-PG:** * **CRS Triad:** Cataract, Sensorineural deafness, and Patent Ductus Arteriosus (PDA). * **Vaccine Type:** Rubella (RA 27/3 strain) is a live attenuated vaccine. It is contraindicated in pregnancy. * **Goal:** The current WHO goal is the elimination of Measles and Rubella by 2023 (extended). * **Note:** While the question reflects a "selective" strategy, in the current **National Immunization Schedule (NIS)**, the MR vaccine is given to both boys and girls to create herd immunity.

Question 250: Cervarix vaccine for HPV contains which strains of virus?

A. HPV 6, 11
B. HPV 16, 18 (Correct Answer)
C. HPV 6, 11, 16, 18
D. HPV 16, 18, 31, 33

Explanation: **Explanation:** The correct answer is **B (HPV 16, 18)**. Cervarix is a **bivalent vaccine** specifically designed to provide protection against the two most high-risk oncogenic strains of Human Papillomavirus (HPV). HPV 16 and 18 are responsible for approximately 70% of all cervical cancer cases globally. **Detailed Analysis of Options:** * **Option B (Correct):** Cervarix contains L1 proteins of HPV types 16 and 18. It is produced using recombinant DNA technology in insect cells and uses a unique adjuvant called **AS04** to enhance the immune response. * **Option A (Incorrect):** HPV 6 and 11 are low-risk strains primarily responsible for **anogenital warts** (Condyloma acuminata), not malignancy. * **Option C (Incorrect):** This describes the **Quadrivalent vaccine (Gardasil)**. Gardasil protects against types 16 and 18 (cancer prevention) as well as types 6 and 11 (wart prevention). * **Option D (Incorrect):** While types 31 and 33 are oncogenic, they are covered by the **Nonavalent vaccine (Gardasil 9)**, which includes types 6, 11, 16, 18, 31, 33, 45, 52, and 58. **High-Yield Clinical Pearls for NEET-PG:** * **Target Age:** The primary target group for the HPV vaccine is girls aged **9–14 years** (before sexual debut). * **Dosage Schedule (IAP/WHO):** * 9–14 years: 2 doses (0, 6 months). * >15 years or immunocompromised: 3 doses (0, 1–2, 6 months). * **Cervavac:** India’s first indigenous quadrivalent HPV vaccine (qHPV) manufactured by the Serum Institute of India. * **Screening:** Vaccination does not replace cervical cancer screening; Pap smears/HPV DNA testing should continue as per protocols.

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Principles of Immunization

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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

Practice Questions

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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