Immunization and Vaccine-Preventable Diseases Practice Questions

Q: Which of the following is a live vaccine?

Bacillus Calmette-Guerin (BCG). **Explanation:** The correct answer is **Bacillus Calmette-Guerin (BCG)**. Vaccines are broadly classified based on the nature of the antigen used. **Live attenuated vaccines** contain a version of the living microbe that has been weakened (attenuated) in the lab so it cannot cause disease in immunocompetent individuals but can still induce a robust immune response. BCG is a live attenuated strain of *Mycobacterium bovis* used to prevent severe forms of tuberculosis (like TB meningitis and miliary TB). **Analysis of Options:** * **Tetanus Toxoid (TT):** This is a **toxoid vaccine**. It contains a modified bacterial toxin that has been rendered non-toxic but remains antigenic. * **DPT (Diphtheria, Pertussis, and Tetanus):** This is a **combination vaccine**. It consists of toxoids (Diphtheria and Tetanus) and either killed whole-cell or acellular components (Pertussis). None of these components are live. * **All of the above:** Incorrect, as only BCG is a live vaccine. **High-Yield Clinical Pearls for NEET-PG:** * **Mnemonic for Live Vaccines:** "**B**oy **L**ove **C**rime **T**he **M**ayor **G**ave **I**n" (**B**CG, **L**ive Influenza, **C**holera (oral), **T**yphoid (Ty21a), **M**MR, **G**astroenteritis (Rotavirus), **I**PV/OPV - note: only **OPV** is live). * **BCG Administration:** It is given **intradermally** (left deltoid). A characteristic permanent scar forms after 6–12 weeks. * **Diluent for BCG:** Normal Saline (NS). Once reconstituted, it must be used within 3–4 hours or discarded to prevent contamination and loss of potency. * **Contraindication:** Live vaccines should generally be avoided in pregnancy and severely immunocompromised individuals (e.g., symptomatic HIV).

Q: Which of the following vaccines should not be given during pregnancy?

Measles, mumps, rubella (MMR) vaccine. **Explanation:** The core 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 congenital anomalies. **Why MMR is the Correct Answer:** The MMR vaccine contains live attenuated viruses for Measles, Mumps, and Rubella. The **Rubella** component is of particular concern because the wild-type virus is highly teratogenic, causing Congenital Rubella Syndrome (CRS). While there is no documented case of CRS from the vaccine itself, the theoretical risk necessitates avoiding it during pregnancy. Women are advised to avoid conception for at least 28 days (4 weeks) after receiving the MMR vaccine. **Analysis of Incorrect Options:** * **Hepatitis B Vaccine:** This is a **recombinant (inactivated)** vaccine. It is safe and indicated during pregnancy if the mother is at high risk of infection. * **Typhoid Vaccine:** The injectable Typhoid vaccine (Vi antigen) is an **inactivated/polysaccharide** vaccine and can be given if the risk of exposure is high. (Note: The oral Ty21a vaccine is live and should be avoided). * **Cholera Vaccine:** Modern oral cholera vaccines (OCVs) are **killed/inactivated** and are considered safe for use in pregnant women during outbreaks or in endemic areas. **High-Yield Clinical Pearls for NEET-PG:** * **Safe in Pregnancy:** Tetanus, Diphtheria, Pertussis (Tdap), Influenza (Inactivated), and Hepatitis B. * **Contraindicated in Pregnancy:** MMR, Varicella, Yellow Fever (unless high-risk travel is unavoidable), and BCG. * **Exception:** If a pregnant woman is exposed to Rabies, the **Rabies vaccine** (inactivated) is given as post-exposure prophylaxis because the benefits outweigh the risks. * **Rule of Thumb:** Inactivated vaccines = Safe; Live vaccines = Avoid.

Q: Post-exposure vaccination for measles should be done within how many days of exposure?

3 days. ### Explanation **Correct Answer: C. 3 days** **1. Why 3 days is correct:** Measles has a relatively long incubation period (average 10–14 days). Post-exposure prophylaxis (PEP) with the **Measles vaccine** is effective if administered within **72 hours (3 days)** of exposure. The rationale is that the vaccine-induced immunity develops faster than the natural infection's progression, potentially preventing the disease or significantly reducing its severity. **2. Analysis of Incorrect Options:** * **A & B (1 and 2 days):** While the vaccine is effective if given during this window, "3 days" is the clinically established upper limit for vaccine efficacy in PEP. * **D (7 days):** By day 7, the virus has already undergone significant replication and systemic spread (viremia). The vaccine is no longer effective at this stage. However, **Immunoglobulin (IG)** can be administered up to **6 days** post-exposure for high-risk individuals. **3. High-Yield Clinical Pearls for NEET-PG:** * **Post-Exposure Prophylaxis (PEP) Summary:** * **Measles Vaccine:** Within 3 days (72 hours). * **Human Immunoglobulin (IG):** Within 6 days. Indicated for infants <6 months, pregnant women, and immunocompromised individuals where the vaccine is contraindicated. * **Vitamin A:** Must be administered to all children with acute measles (2 doses, 24 hours apart) to prevent complications like blindness and pneumonia. * **Isolation:** A patient with measles is infectious from **4 days before to 4 days after** the appearance of the rash. * **Secondary Attack Rate (SAR):** Measles has a very high SAR (>90%), making it one of the most contagious diseases.

Q: BCG vaccine should be administered:

Immediately after birth. **Explanation:** **1. Why Option A is Correct:** Under the National Immunization Schedule (NIS) in India, the BCG (Bacillus Calmette-Guérin) vaccine is recommended **at birth** or as soon as possible thereafter. The primary medical rationale is to provide early protection against severe, disseminated forms of childhood tuberculosis, such as **Tubercular Meningitis** and **Miliary Tuberculosis**. Since newborns in endemic areas like India are at immediate risk of exposure, early administration ensures the induction of cell-mediated immunity before natural infection occurs. **2. Why Other Options are Incorrect:** * **Options B, C, and D:** Delaying the vaccine until 6 months or 1 year increases the window of vulnerability for the infant to contract life-threatening TB. While BCG can be given up to the age of **one year** if missed at birth, it is not the "recommended" timing. Beyond one year, the vaccine is generally not administered under the routine NIS because most children in endemic areas would have already been exposed to environmental mycobacteria or *M. tuberculosis*. **3. High-Yield Clinical Pearls for NEET-PG:** * **Type of Vaccine:** Live attenuated (derived from *Mycobacterium bovis*). * **Dose:** 0.05 ml (until 1 month of age); 0.1 ml (beyond 1 month up to 1 year). * **Route & Site:** Strictly **Intradermal** (ID) using an Omega/Tuberculin syringe; Left upper arm (deltoid region). * **Diluent:** Normal Saline (NS). *Note: Distilled water is never used as it causes irritation.* * **The BCG Scar:** Follows a specific sequence: Papule (2-3 weeks) → Pustule/Ulcer (5-6 weeks) → Permanent depressed scar (6-12 weeks). * **Direct BCG:** Giving the vaccine without a prior Mantoux test (standard practice for infants). * **Contraindication:** BCG is contraindicated in individuals with symptomatic HIV infection or severe immunodeficiency.

Q: At the Primary Health Centre (PHC) level, where are vaccines stored?

Ice-lined refrigerator. ### Explanation **Correct Answer: C. Ice-lined refrigerator (ILR)** At the **Primary Health Centre (PHC)** level, the **Ice-lined Refrigerator (ILR)** is the backbone of the cold chain. It is designed to maintain a stable temperature between **+2°C to +8°C**, even during power outages of up to 20 hours, due to the lining of water-filled ice packs or tubes along the cabinet walls. In the Universal Immunization Programme (UIP), ILRs at the PHC level are used to store all vaccines (both heat-sensitive and freeze-sensitive). **Analysis of Incorrect Options:** * **A. Cold Box:** These are insulated containers used for **bulk transportation** of vaccines from district stores to PHCs or for temporary storage during emergencies/maintenance. They are not used for routine permanent storage at the PHC. * **B. Deep Freezer:** At the PHC level, deep freezers are primarily used for **preparing and freezing ice packs**. While they can store OPV and Measles vaccines at the district level (-15°C to -25°C), the ILR is the primary storage unit for all vaccines at the PHC. * **D. Walk-in Cold Room (WIC):** These are large-scale storage facilities located at **Regional or District levels** to supply large populations. They are too large and resource-intensive for the PHC level. **High-Yield Clinical Pearls for NEET-PG:** * **Cold Chain Levels:** * **Regional/State:** Walk-in Coolers (WIC) and Walk-in Freezers (WIF). * **District:** Large ILRs and Deep Freezers. * **PHC:** Small ILRs and Deep Freezers. * **Sub-centre/Session Site:** Vaccine Carriers (last link). * **Storage Rule:** In an ILR, **T**etanus Toxoid (TT/Td), Hep B, and DPT (freeze-sensitive) are kept at the **top**, while OPV and Measles (heat-sensitive) are kept at the **bottom** (the coolest part). * **Thermometer:** A **Dial Thermometer** or **Stem Thermometer** is used to monitor the temperature twice daily.

Q: A 3-year-old completely unimmunized child presents to an immunization clinic for the first time. What vaccines and supplements should be administered?

DPT-1, OPV-1, Measles, Vitamin-A. **Explanation:** The management of a "late starter" or unimmunized child depends on the age of presentation and the upper age limits for specific vaccines under the National Immunization Schedule (NIS) in India. **1. Why Option D is Correct:** * **DPT:** Can be given up to 7 years of age. Since the child is 3 years old, DPT-1 is initiated. * **OPV:** Can be given up to 5 years of age. * **Measles (MR):** Can be given up to 5 years of age. * **Vitamin A:** The first dose is usually given at 9 months, followed by doses every 6 months up to 5 years. * **Note on Pentavalent:** While Pentavalent is used in the routine schedule, for a child >1 year, the Hepatitis B and Hib components are generally not prioritized in catch-up unless specifically indicated; however, DPT remains the backbone of the catch-up. **2. Why Other Options are Incorrect:** * **Option A & C (BCG):** BCG is administered at birth. According to NIS guidelines, the **upper age limit for BCG is 1 year**. Since the child is 3 years old, BCG is no longer indicated. * **Option B (DT):** DT (Dual Toxoid) is used as a replacement for DPT only in children **above 7 years of age** (to avoid the systemic reaction of the whole-cell Pertussis component in older children). For a 3-year-old, DPT is the correct choice. **High-Yield NEET-PG Pearls:** * **Upper Age Limits:** * **BCG:** 1 year. * **Rotavirus/Pentavalent/PCV:** 1 year. * **OPV/Measles/DPT:** 5 years (DPT can be extended to 7 years). * **JE Vaccine:** 15 years. * **Vitamin A:** Total 9 doses (1 lakh IU at 9 months; 2 lakh IU every 6 months thereafter until 5 years). Total cumulative dose: 17 lakh IU. * **Injection Site:** If multiple vaccines are given, use different limbs or sites separated by at least 1 inch.

Q: Which of the following are live vaccines?

BCG, OPV, MMR. **Explanation:** The core concept behind this question is the classification of vaccines based on their preparation method. **Live attenuated vaccines** contain a version of the living microbe that has been weakened (attenuated) in the lab so it cannot cause disease in immunocompetent individuals but can still induce a robust immune response. **Why Option C is Correct:** * **BCG (Bacillus Calmette-Guérin):** A live bacterial vaccine derived from *Mycobacterium bovis*. * **OPV (Oral Polio Vaccine/Sabin):** A live attenuated viral vaccine. * **MMR (Measles, Mumps, Rubella):** A combination of three live attenuated viral components. All three components in this option are live vaccines, making it the most accurate choice. **Analysis of Incorrect Options:** * **Option A & B:** These include **TT (Tetanus Toxoid)** and **DPT**. TT is a **toxoid** (inactivated toxin), and the 'P' in DPT (Pertussis) is typically **killed/inactivated** (though acellular versions exist). * **Option D:** While both OPV and MMR are live vaccines, this option is less complete than Option C, which includes BCG. **High-Yield Clinical Pearls for NEET-PG:** * **Mnemonic for Live Vaccines:** "**B**oy **R**omeo **G**ive **M**y **L**ove **S**picy **V**ictory **T**onight" (**B**CG, **R**otavirus, **G**umbaro/not human, **M**MR, **L**ive Typhoid [Ty21a], **S**abin/OPV, **V**aricella, **Y**ellow Fever). * **Contraindications:** Live vaccines are generally contraindicated in **pregnancy** and **immunocompromised** states (e.g., HIV with CD4 <200). * **Storage:** Most live vaccines are heat-sensitive and must be stored in the freezer or the coldest part of the ILR (except BCG and Measles after reconstitution). * **Reconstitution:** BCG and Measles vaccines must be used within **4 hours** of reconstitution to prevent Toxic Shock Syndrome (usually caused by *Staph. aureus* contamination).

Question 1

Which of the following is a live vaccine?

Accepted Answer

Bacillus Calmette-Guerin (BCG)

Answer

Tetanus toxoid (TT)

Answer

Diphtheria, Pertussis, and Tetanus (DPT)

Answer

All of the above

Question 2

Which of the following vaccines should not be given during pregnancy?

Accepted Answer

Measles, mumps, rubella (MMR) vaccine

Answer

Hepatitis B vaccine

Answer

Typhoid vaccine

Answer

Cholera vaccine

Question 3

Post-exposure vaccination for measles should be done within how many days of exposure?

Accepted Answer

3 days

Answer

1 day

Answer

2 days

Answer

7 days

Question 4

Which of the following does not increase the immunological effectiveness of DPT vaccine?

Accepted Answer

Hib polysaccharide conjugated to diphtheria toxoid

Answer

Aluminium phosphate

Answer

Inactivated whole cell pertussis vaccine

Answer

Purified and detoxified components of B. pertussis

Question 5

BCG vaccine should be administered:

Accepted Answer

Immediately after birth

Answer

At 6 months of age

Answer

At 1 year of age

Answer

Any time after 1 year of age

Question 6

Which of the following is a newer Influenza vaccine?

Accepted Answer

Killed vaccine

Answer

Split-virus vaccine

Answer

Neuraminidase

Answer

Live attenuated vaccine

Question 7

At the Primary Health Centre (PHC) level, where are vaccines stored?

Accepted Answer

Ice-lined refrigerator

Answer

Cold box

Answer

Deep freezer

Answer

Walk-in cold room

Question 8

What is defined as 'ring vaccination'?

Accepted Answer

Administered to individuals within a defined radius of a detected case

Answer

Administered by a ring-shaped machine

Answer

Given to produce a ring lesion

Answer

Administered to individuals within approximately one mile of a detected case

Question 9

A 3-year-old completely unimmunized child presents to an immunization clinic for the first time. What vaccines and supplements should be administered?

Accepted Answer

DPT-1, OPV-1, Measles, Vitamin-A

Answer

BCG, Measles, Vitamin-A

Answer

DT-1, OPV-1, Measles, Vitamin-A

Answer

BCG, DPT-1, OPV-1, Measles, Vitamin-A

Question 10

Which of the following are live vaccines?

Accepted Answer

BCG, OPV, MMR

Answer

TT, BCG

Answer

BCG, DPT, TT

Answer

OPV, MMR

Immunization and Vaccine-Preventable Diseases — MCQs

Immunization and Vaccine-Preventable Diseases — MCQs

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