Immunization and Vaccine-Preventable Diseases Practice Questions

Q: Which of the following is a contraindication to receiving the live rubella vaccine?

Pregnant women. **Explanation:** The rubella vaccine is a **live-attenuated virus vaccine** (RA 27/3 strain). The primary contraindication for any live vaccine is pregnancy, due to the theoretical risk of the attenuated virus crossing the placenta and causing **Congenital Rubella Syndrome (CRS)** in the fetus [1]. While no cases of CRS have been documented from the vaccine itself, the risk remains a medical concern. **Analysis of Options:** * **D (Correct):** Pregnant women should not receive the vaccine. Furthermore, women are advised to avoid pregnancy for at least **4 weeks (28 days)** after receiving the rubella or MMR vaccine. * **A & B:** Rubella vaccination is routinely indicated for children. In India’s National Immunization Schedule, the MR/MMR vaccine is given at **9 months** and **16–24 months**. It is not given to infants under 6–9 months because maternal antibodies can interfere with the immune response. * **C:** Vaccination is recommended for non-pregnant adults who lack evidence of immunity, particularly healthcare workers and women of childbearing age (pre-conception), to prevent future outbreaks and CRS. **High-Yield Clinical Pearls for NEET-PG:** * **Post-partum Vaccination:** If a woman is found to be seronegative during pregnancy, she should be vaccinated immediately in the **immediate postpartum period**. Breastfeeding is *not* a contraindication. * **Egg Allergy:** Unlike the influenza vaccine, MMR is grown in chick embryo fibroblast cultures, not eggs; therefore, a history of egg allergy is **not** a contraindication. * **Immunocompromised states:** Like all live vaccines, it is contraindicated in severely immunocompromised individuals (e.g., HIV with CD4 <200), except for household contacts of such patients. [1]

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: 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: The DPT vaccine is administered via which route?

Intramuscular. **Explanation:** The **DPT (Diphtheria, Pertussis, and Tetanus)** vaccine is a combination vaccine administered via the **Intramuscular (IM)** route. In infants, the preferred site is the **anterolateral aspect of the mid-thigh**, as this area has the largest muscle mass (vastus lateralis) and avoids potential injury to the sciatic nerve. **Why Intramuscular?** DPT contains **adjuvants** (like aluminum salts) designed to enhance the immune response. These adjuvants are highly irritating to the skin and subcutaneous tissues. Injecting deep into the muscle ensures slow absorption and minimizes local reactions. **Analysis of Incorrect Options:** * **Subcutaneous:** This route is avoided for DPT because the adjuvants can cause **sterile abscesses**, localized tissue necrosis, and severe irritation if deposited in the fatty layer. (Note: Measles and Yellow Fever vaccines are typically subcutaneous). * **Intradermal:** This route is used for vaccines requiring a slow release and specific immune cell interaction, such as **BCG** or the **Rabies** vaccine (IDRV). DPT would cause significant skin damage if given this way. * **Intravenous:** Vaccines are never administered intravenously as they need to be processed by local immune cells and can cause systemic anaphylaxis if injected directly into the bloodstream. **High-Yield Clinical Pearls for NEET-PG:** * **Site:** Anterolateral thigh (Infants); Deltoid (Older children/Adults). * **Angle:** 90 degrees. * **Storage:** DPT is **heat-stable but freeze-sensitive**. It must be stored at +2°C to +8°C. If frozen, it loses potency (perform the **Shake Test** to check for damage). * **Pentavalent Vaccine:** In the National Immunization Schedule, DPT is now part of the Pentavalent vaccine (DPT + Hep B + Hib), also given IM.

Q: The frozen DPT vaccine should be handled in which of the following ways before use?

Discarded. **Explanation:** The correct answer is **Discarded**. This is based on the fundamental principle of the **"Shake Test"** and the stability of adsorbed vaccines. **1. Why "Discarded" is correct:** DPT (Diphtheria, Pertussis, and Tetanus) is an **adsorbed vaccine**, where antigens are fixed onto an adjuvant (aluminum salts). These vaccines are highly **freeze-sensitive**. When frozen, the aluminum lattice structure crystallizes and breaks, causing the antigen to detach and form large, heavy aggregates. This process is irreversible. Once thawed, these clumps settle rapidly at the bottom of the vial, leading to: * **Loss of potency:** The vaccine no longer provides adequate immunity. * **Increased reactogenicity:** The large aggregates can cause severe local reactions or sterile abscesses at the injection site. **2. Why other options are incorrect:** * **Shaken thoroughly (A):** While shaking is required for normal DPT to ensure a uniform suspension, it cannot reverse the structural damage caused by freezing. * **Allowed to melt (B) / Brought to room temperature (D):** Simply returning the vaccine to a liquid state or room temperature does not restore the chemical integrity of the aluminum adjuvant or the antigen-adjuvant bond. **3. High-Yield Clinical Pearls for NEET-PG:** * **Freeze-Sensitive Vaccines:** Remember the mnemonic **"DPT-HepB-TT"** (DPT, Hepatitis B, Tetanus Toxoid, and Pentavalent). These must be stored between **+2°C to +8°C** and never in the freezer. * **The Shake Test:** If freezing is suspected, perform the Shake Test. Compare the suspect vial with a control vial (never frozen). If the suspect vial settles faster than the control, it has been damaged and must be discarded. * **Storage Location:** In an ILR (Ice-Lined Refrigerator), freeze-sensitive vaccines are kept at the **top**, furthest from the cooling coils.

Q: Live vaccines are contraindicated in all of the following EXCEPT:

Breastfeeding. **Explanation:** The core principle behind contraindications for live vaccines is the risk of uncontrolled viral or bacterial replication in a host with an altered immune system or a physiological state where fetal transmission is a concern. **1. Why Breastfeeding is the Correct Answer:** Breastfeeding is **not** a contraindication for live vaccines. Most live vaccines (e.g., MMR, Varicella) do not pass into breast milk, and even if they do, they do not cause disease in the infant. In fact, vaccinating a breastfeeding mother is often encouraged to protect the infant through "cocooning." The only rare exception is the Yellow Fever vaccine, which is avoided in breastfeeding mothers unless travel to an endemic area is unavoidable. **2. Analysis of Incorrect Options:** * **Pregnancy:** Live vaccines (especially MMR and Varicella) are contraindicated due to the theoretical risk of vertical transmission to the fetus, potentially causing congenital rubella syndrome or other teratogenic effects. * **HIV (Symptomatic/Immunosuppressed):** While asymptomatic HIV patients can receive some live vaccines (like MMR or BCG in specific protocols), live vaccines are generally contraindicated in those with severe immunosuppression (CD4 count 14 days) suppress the cell-mediated immune response, making live vaccines unsafe. **Clinical Pearls for NEET-PG:** * **Yellow Fever Vaccine:** Contraindicated in infants <6 months, pregnant women, and those with thymus disorders or egg allergy. * **Interval Rule:** Two live injectable vaccines must be given either on the same day or at least 4 weeks apart. * **HIV Exception:** BCG is contraindicated in all HIV-positive children (symptomatic or asymptomatic) according to WHO guidelines in high-prevalence areas.

Question 1

Which of the following is a contraindication to receiving the live rubella vaccine?

Accepted Answer

Pregnant women

Answer

Children between 1 year old and puberty

Answer

Infants less than 1 year old

Answer

All adults

Question 2

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 3

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 4

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 5

The DPT vaccine is administered via which route?

Accepted Answer

Intramuscular

Answer

Subcutaneous

Answer

Intradermal

Answer

Intravenous

Question 6

Which of the following vaccines is contraindicated in pregnancy?

Accepted Answer

Hepatitis B

Answer

BCG

Answer

OPV

Answer

Yellow fever

Question 7

The frozen DPT vaccine should be handled in which of the following ways before use?

Accepted Answer

Discarded

Answer

Shaken thoroughly before use

Answer

Allowed to melt before use

Answer

Brought to room temperature before use

Question 8

Under the National Polio Eradication Programme, a case of Acute Flaccid Paralysis (AFP) is confirmed as Polio under which of the following circumstances, except?

Accepted Answer

If a patient develops paralysis 30 days after diagnosis of AFP

Answer

If a case is lost to follow-up

Answer

If a case could not be confirmed because the patient died before confirmation

Answer

If a wild strain of poliovirus is isolated from the stool

Question 9

Live vaccines are contraindicated in all of the following EXCEPT:

Accepted Answer

Breastfeeding

Answer

Pregnancy

Answer

HIV (asymptomatic)

Answer

Steroid-dependent immunosuppression

Question 10

Vaccine-associated paralytic poliomyelitis is defined as those cases of acute flaccid paralysis who have residual weakness and from whose stool samples, vaccine-related poliovirus but no wild virus is isolated?

Accepted Answer

60 days after the onset of paralysis

Answer

6 months after the onset of paralysis

Answer

6 days after the onset of paralysis

Answer

60 days after the onset of paralysis and from whose stool samples, wild polio virus is isolated.

Immunization and Vaccine-Preventable Diseases — MCQs

Immunization and Vaccine-Preventable Diseases — MCQs

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