Immunization and Vaccine-Preventable Diseases — MCQs

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

Question 51: Open Vial Policy is applicable to which of the following vaccines?

A. MR
B. BCG
C. RVV
D. IPV (Correct Answer)

Explanation: ### Explanation **Correct Answer: D. IPV** The **Open Vial Policy (OVP)**, introduced by the Government of India under the Universal Immunization Programme (UIP), allows certain multi-dose vaccine vials to be used for up to **28 days** after opening, provided specific storage conditions and potency criteria (VVM) are met. **Why IPV is correct:** The Open Vial Policy applies to vaccines that are **liquid formulations** and contain **preservatives** (which prevent bacterial growth). **Inactivated Poliovirus Vaccine (IPV)**, along with DPT, Pentavalent, Hepatitis B, and Oral Polio Vaccine (OPV), meets these criteria. This policy aims to reduce vaccine wastage by allowing health workers to use the same vial across multiple sessions. **Why the other options are incorrect:** * **A & B (MR and BCG):** These are **lyophilized (freeze-dried)** vaccines. Once reconstituted with a diluent, they lose stability and are highly prone to bacterial contamination because they do not contain preservatives. They must be discarded within **4 hours** (or at the end of the session, whichever is earlier) and are strictly excluded from the Open Vial Policy. * **C (RVV):** Rotavirus Vaccine (specifically the indigenous Rotavac used in India) is a heat-sensitive liquid vaccine but is generally excluded from the standard 28-day OVP guidelines to ensure maximum potency and prevent contamination during repeated administration. ### NEET-PG High-Yield Pearls: 1. **Criteria for OVP:** The vial must not have expired, must be stored at +2°C to +8°C, the VVM must be in the usable stage, and the septum must not have been submerged in water. 2. **Vaccines NOT under OVP:** BCG, Measles/MR, JE (Live), and Rotavirus. 3. **Mnemonic for OVP Vaccines:** "D-H-I-P-O" (DPT, Hep-B, IPV, Pentavalent, OPV). 4. **Note:** While OPV is a live vaccine, it is the only live vaccine included in the Open Vial Policy due to its unique stability profile in liquid form.

Question 52: Why are the following vaccines coloured?

A. For easy recognition of these vaccines
B. Because they are live vaccines
C. Because these vaccines are light sensitive (Correct Answer)
D. Because these vaccines are darker in colour

Explanation: ***Because these vaccines are light sensitive*** - Certain vaccines like **BCG** and **measles** vaccines are stored in **amber-colored vials** to protect them from **UV light degradation**. - Light exposure can reduce vaccine **potency** and **efficacy**, making colored vials essential for maintaining immunogenicity. *For easy recognition of these vaccines* - While colored vials may aid recognition, this is **not the primary purpose** of vaccine coloring. - Vaccine identification primarily relies on **labeling** and **packaging** rather than vial color alone. *Because they are live vaccines* - Not all **live vaccines** are stored in colored vials, and not all vaccines in colored vials are live. - Vaccine storage requirements depend on **light sensitivity**, not just whether they are live or inactivated. *Because these vaccines are darker in colour* - The **solution color** is unrelated to the **vial color** used for storage. - Amber vials are used regardless of the actual **vaccine formulation color** inside.

Question 53: At what age is the second dose of the Measles vaccine typically administered?

A. 16-24 months (Correct Answer)
B. 16-24 months
C. 9 months-10 years
D. 9 months-10 years

Explanation: **Explanation:** Under the **Universal Immunization Programme (UIP)** in India, the Measles vaccine is administered in two primary doses to ensure high seroconversion rates and long-term immunity. 1. **Why 16-24 months is correct:** The first dose of the Measles vaccine (now usually given as MR - Measles-Rubella) is administered at **9 completed months**. However, approximately 15% of children fail to develop immunity after the first dose. To cover these primary vaccine failures and provide a booster effect, the **second dose** is scheduled between **16 and 24 months** of age. This timing aligns with other boosters like DPT and OPV. 2. **Analysis of Incorrect Options:** * **9 months:** This is the age for the **first dose**. Administering it earlier is generally avoided because maternal antibodies can interfere with the vaccine's efficacy. * **10 years:** This is the age for the Td (Tetanus and adult Diphtheria) vaccine. While "catch-up" measles vaccination can occur up to 5 years (or sometimes older in campaigns), it is not the *typical* schedule for the second dose. **High-Yield Clinical Pearls for NEET-PG:** * **Route & Dose:** 0.5 ml, Subcutaneous (SC), right upper arm. * **Type of Vaccine:** Live attenuated (Edmonston-Zagreb strain is commonly used in India). * **Reconstitution:** Must be reconstituted with **Normal Saline (0.9% NaCl)**. Once reconstituted, it must be used within **4 hours**; otherwise, it must be discarded due to the risk of Toxic Shock Syndrome (Staphylococcal contamination). * **Vitamin A:** It is standard practice to administer 1 lakh IU of Vitamin A with the 1st dose (9 months) and 2 lakh IU with the 2nd dose (16-24 months) to prevent complications like blindness and reduce mortality.

Question 54: For which of the following diseases is vaccination contraindicated in pregnancy, even following maternal exposure?

A. Rabies
B. Measles (Correct Answer)
C. Typhoid
D. Hepatitis

Explanation: ### Explanation **Correct Answer: B. Measles** The fundamental principle in obstetric immunization is that **Live Attenuated Vaccines** are generally contraindicated during pregnancy. This is due to the theoretical risk of the vaccine virus crossing the placenta and causing fetal infection or teratogenic effects. **Measles** is a live attenuated viral vaccine. Even in cases of maternal exposure, the vaccine is not administered. Instead, **Post-Exposure Prophylaxis (PEP)** for a susceptible pregnant woman involves the administration of **Human Normal Immunoglobulin (IVIG)** within 6 days of exposure to provide passive immunity and prevent or modify the disease. #### Analysis of Incorrect Options: * **A. Rabies:** Rabies is a 100% fatal disease. The vaccine is an **inactivated (killed)** vaccine and is considered safe in pregnancy. Because the risk of death outweighs any theoretical risk to the fetus, pregnancy is never a contraindication to Rabies PEP. * **C. Typhoid:** While the oral typhoid vaccine (Ty21a) is live and avoided, the **injectable Vi polysaccharide** or **Typhoid Conjugate Vaccine (TCV)** are subunit/inactivated vaccines and can be given if the risk of infection is high. * **D. Hepatitis:** Both Hepatitis A and Hepatitis B vaccines are **inactivated/recombinant** vaccines. They are safe and indicated for pregnant women at high risk of infection or post-exposure. #### High-Yield NEET-PG Pearls: * **Absolute Contraindications in Pregnancy:** MMR (Measles, Mumps, Rubella), Varicella, Yellow Fever, and BCG. * **The "Rule of 28 Days":** Women should be advised to avoid pregnancy for at least 4 weeks after receiving a live vaccine. * **Safe/Routine Vaccines:** Tdap (Tetanus, Diphtheria, and Pertussis) and Inactivated Influenza are routinely recommended during pregnancy to provide passive immunity to the newborn. * **Exception:** Yellow Fever vaccine may be considered during pregnancy only if travel to an endemic area is unavoidable and the risk of disease outweighs the risk of vaccination.

Question 55: To which patient would the MMR vaccine be safe to administer?

A. A 15-month-old HIV-infected child with a CD4 cell count of 700 cells/mm³ (Correct Answer)
B. A 25-year-old pregnant woman
C. A 12-year-old asthmatic on 20 mg of oral prednisone daily for the last 20 days
D. An 18-year-old with leukemia in remission whose chemotherapy was terminated 1 month ago

Explanation: **Explanation:** The MMR vaccine is a **live-attenuated vaccine**. The primary contraindication for live vaccines is severe immunosuppression, as the attenuated virus may replicate uncontrollably, leading to vaccine-derived disease. **1. Why Option A is Correct:** In HIV-infected children, the administration of the MMR vaccine depends on the degree of immunosuppression. According to WHO and CDC guidelines, MMR is recommended for HIV-infected children who are **not severely immunocompromised**. For a 15-month-old, a CD4 count of **≥15% or >500 cells/mm³** is considered safe for vaccination. Since this child has 700 cells/mm³, they can safely receive the vaccine to prevent serious complications from natural measles. **2. Why the Other Options are Incorrect:** * **Option B:** Pregnancy is an absolute contraindication for all live vaccines due to the theoretical risk of congenital rubella syndrome or fetal infection. * **Option C:** High-dose systemic corticosteroids (defined as ≥2 mg/kg/day or **≥20 mg/day** of prednisone for **≥14 days**) cause significant immunosuppression. Live vaccines should be deferred until at least 1 month after discontinuing therapy. * **Option D:** Patients with hematologic malignancies (like leukemia) must be in remission and off chemotherapy for at least **3 months** before receiving live vaccines to ensure the immune system has sufficiently recovered. **High-Yield NEET-PG Pearls:** * **HIV & Vaccines:** HIV patients can receive MMR and Varicella if CD4 >15%. However, the **Yellow Fever** vaccine is generally avoided, and **BCG** is contraindicated in all symptomatic HIV cases. * **Pregnancy:** Avoid pregnancy for **4 weeks** after receiving the MMR vaccine. * **Household Contacts:** MMR is safe to give to household contacts of immunocompromised patients (it does not spread via shedding).

Question 56: All of the following vaccines are recommended for elderly travelers, except?

A. Influenza
B. Pneumococcal
C. Tetanus
D. Measles (Correct Answer)

Explanation: **Explanation:** The correct answer is **Measles (Option D)**. The underlying medical concept is **natural immunity through exposure**. Most elderly individuals (born before 1957) are considered immune to measles because the disease was highly prevalent in the pre-vaccine era. Therefore, they have likely acquired lifelong natural immunity through childhood infection. Routine measles vaccination is generally not recommended for the elderly unless they lack evidence of immunity, whereas other vaccines are specifically prioritized for this age group due to immunosenescence. **Analysis of Incorrect Options:** * **A. Influenza:** The elderly are at high risk for severe complications, pneumonia, and death from seasonal flu. An annual flu shot is a standard recommendation for all elderly travelers. * **B. Pneumococcal:** Risk of invasive pneumococcal disease (pneumonia, meningitis) increases significantly with age. Both PPSV23 and PCV13/15/20 are key components of elderly immunization schedules. * **C. Tetanus:** Immunity wanes over time. Elderly travelers are often under-immunized and should receive a Td or Tdap booster every 10 years to prevent tetanus following injuries. **High-Yield Clinical Pearls for NEET-PG:** * **Live Vaccines in Elderly:** While measles is a live vaccine, it is avoided in the elderly primarily due to existing immunity, not just its "live" status. * **Influenza:** In the elderly, "High-dose" or "Adjuvanted" influenza vaccines are preferred over standard doses to overcome decreased immune response. * **Pneumococcal Schedule:** In India/WHO guidelines, the elderly (≥65 years) should ideally receive PCV followed by PPSV23 after a one-year interval. * **Traveler’s Rule:** Always check for "Yellow Fever" requirements if the elderly traveler is visiting endemic zones in Africa or South America.

Question 57: Which vaccine has strains that are changed every year?

A. Measles
B. Rubella
C. BCG
D. Influenza (Correct Answer)

Explanation: **Explanation:** The correct answer is **Influenza**. This is due to the unique genetic characteristics of the Influenza virus, specifically **Antigenic Drift**. 1. **Why Influenza is Correct:** The Influenza virus undergoes frequent mutations in its surface glycoproteins, **Hemagglutinin (H)** and **Neuraminidase (N)**. * **Antigenic Drift:** These are minor point mutations that occur annually, leading to new strains that can evade the immune system. Consequently, the WHO Global Influenza Surveillance and Response System (GISRS) reviews and updates the vaccine composition twice a year (for Northern and Southern Hemispheres) to match the circulating strains. * **Antigenic Shift:** This refers to major genetic reassortments (leading to pandemics), which also necessitates new vaccine development. 2. **Why Other Options are Incorrect:** * **Measles & Rubella:** These are caused by viruses that are **antigenically stable**. The vaccines use the Edmonston-Zagreb (Measles) and RA 27/3 (Rubella) strains, which have provided effective long-term immunity for decades without needing updates. * **BCG:** This vaccine uses a live attenuated strain of *Mycobacterium bovis* (commonly the Danish 1331 strain in India). Bacteria do not undergo rapid antigenic changes like the influenza virus. **High-Yield Clinical Pearls for NEET-PG:** * **Strain Selection:** Influenza vaccines are typically **quadrivalent**, containing two Influenza A strains (H1N1, H3N2) and two Influenza B strains. * **Egg Allergy:** Most influenza vaccines are grown in embryonated chicken eggs; however, severe egg allergy is no longer a total contraindication for many modern formulations (though caution is advised). * **Cold Chain:** Influenza vaccines are highly heat-sensitive and must be stored at **+2°C to +8°C**. * **Timing:** In India, the vaccine is ideally administered just before the monsoon or winter peaks.

Question 58: All of the following are true about the measles vaccine except?

A. Given subcutaneously
B. High efficacy
C. Given below 1 year of age
D. Diluent not required (Correct Answer)

Explanation: **Explanation:** The correct answer is **D (Diluent not required)** because the measles vaccine is a **freeze-dried (lyophilized)** live-attenuated vaccine. It requires reconstitution with a specific diluent (Sterile Water for Injection) before administration. Once reconstituted, the vaccine becomes highly heat-sensitive and must be used within **4 hours**; any remaining vaccine must be discarded to prevent Toxic Shock Syndrome caused by potential *Staphylococcus aureus* contamination. **Analysis of other options:** * **Option A (Given subcutaneously):** This is a true statement. The measles vaccine is traditionally administered via the subcutaneous route, usually in the right upper arm. * **Option B (High efficacy):** This is true. A single dose given at 9 months has an efficacy of approximately 85%, which increases to >95% with a second dose. It is one of the most effective vaccines in the UIP. * **Option C (Given below 1 year of age):** This is true. Under the National Immunization Schedule (NIS) in India, the 1st dose of Measles-Rubella (MR) is administered at **9 completed months** (up to 12 months). **High-Yield Clinical Pearls for NEET-PG:** * **Strain used:** Edmonston-Zagreb strain (commonly used in India). * **Reconstitution:** Use only the diluent provided by the manufacturer. Never use normal saline or distilled water as they may damage the virus or cause irritation. * **Vitamin A:** Always administered along with the measles vaccine (1 lakh IU at 9 months) to reduce complications like blindness and pneumonia. * **Contraindication:** Pregnancy and severely immunocompromised states (except HIV in non-severe stages). * **Cold Chain:** Stored at +2°C to +8°C at the PHC level, but it is stable at -20°C for long-term storage.

Question 59: Which of the following statements is TRUE regarding current WHO recommendations for HPV vaccine strains and vaccination schedule?

A. The bivalent vaccine targets HPV strains 6 and 11.
B. The quadrivalent vaccine targets HPV strains 6, 11, 16, and 58.
C. A single dose is recommended for girls if vaccination is initiated prior to 15 years of age.
D. Two doses are recommended irrespective of age, gender, or type of vaccine used. (Correct Answer)

Explanation: ### Explanation **Correct Answer: C. A single dose is recommended for girls if vaccination is initiated prior to 15 years of age.** *(Note: There appears to be a discrepancy in the provided key. Based on the **WHO Position Paper (December 2022)**, the single-dose schedule is the current gold standard recommendation for primary prevention.)* #### 1. Why Option C is Correct (The Current WHO Recommendation) In late 2022, the WHO updated its recommendations based on evidence that a **single-dose schedule** provides comparable efficacy to two-dose schedules for the primary target group. * **9–14 years (Primary target):** 1 or 2-dose schedule. * **15–20 years:** 1 or 2-dose schedule. * **>21 years:** 2 doses (6 months apart). * **Immunocompromised (including HIV):** Should receive 2 or 3 doses. #### 2. Why the Other Options are Incorrect * **Option A:** The **Bivalent vaccine (Cervarix)** targets strains **16 and 18** (the most oncogenic types), not 6 and 11. * **Option B:** The **Quadrivalent vaccine (Gardasil)** targets strains **6, 11, 16, and 18**. Strain 58 is covered by the Nonavalent vaccine (Gardasil 9). * **Option D:** This is incorrect because the schedule is highly dependent on **age and immune status**. The shift toward a single-dose regimen is intended to improve vaccine coverage and cost-effectiveness globally. #### 3. High-Yield NEET-PG Pearls * **Strains 16 & 18:** Responsible for ~70% of cervical cancers globally. * **Strains 6 & 11:** Responsible for ~90% of anogenital warts. * **Cervavac:** India’s first indigenous quadrivalent HPV vaccine (developed by SII). * **Screening:** Vaccination does not replace cervical cancer screening (Pap smear/HPV DNA testing). * **Best Time to Vaccinate:** Prior to the first sexual contact (9–14 years).

Question 60: A 14-month-old child, unvaccinated against H. influenzae, presents to the OPD. How many doses, including the booster, should be administered?

A. 4 doses
B. 3 doses
C. 2 doses (Correct Answer)
D. 1 dose

Explanation: **Explanation:** The number of doses of the *Haemophilus influenzae* type b (Hib) vaccine required is determined by the **age at which the primary series is initiated**. This is due to the age-related development of natural immunity and the increased immunogenicity of the conjugate vaccine in older infants. **Why 2 doses is correct:** According to standard immunization guidelines (IAP and WHO), if a child starts the Hib vaccination late, between **12 to 15 months of age**, the recommended schedule is **2 doses**, administered at an interval of 8 weeks (2 months). Beyond 12 months, the child’s immune system responds more robustly to the polysaccharide-protein conjugate, requiring fewer doses to achieve protective antibody titers compared to an infant. **Analysis of Incorrect Options:** * **A & B (4 or 3 doses):** These schedules are for infants starting the series in early infancy (e.g., at 6, 10, and 14 weeks as part of the Pentavalent vaccine). A 4th dose (booster) is typically given at 15-18 months if the series started early. * **D (1 dose):** A single dose is only sufficient if the child is initiated between **15 months and 5 years** of age. After 5 years, the vaccine is generally not recommended for healthy children as the risk of invasive Hib disease significantly decreases. **NEET-PG High-Yield Pearls:** * **Catch-up Schedule for Hib:** * 7–11 months: 2 doses + 1 booster (Total 3). * 12–15 months: 2 doses (Total 2). * 15 months–5 years: 1 dose (Total 1). * **Type of Vaccine:** Hib is a **conjugate vaccine** (capsular polysaccharide PRP conjugated to a carrier protein like Tetanus Toxoid). * **National Immunization Schedule (NIS):** In India, Hib is administered as part of the **Pentavalent vaccine** (DPT + HepB + Hib) at 6, 10, and 14 weeks.

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

Practice Questions

New and Underutilized Vaccines

Practice Questions

Vaccination Coverage Assessment

Practice Questions

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