Immunization and Vaccine-Preventable Diseases Practice Questions

Q: The MMR vaccine is controversially associated with which of the following conditions?

Autism. **Explanation:** The association between the **MMR (Measles, Mumps, and Rubella) vaccine and Autism** is one of the most famous controversies in medical history. It originated from a 1998 paper by Andrew Wakefield published in *The Lancet*, which suggested a link between the vaccine and "autistic enterocolitis." However, the study was later found to be fraudulent, based on manipulated data, and was fully retracted. Extensive global epidemiological studies have since proven **no causal link** between the MMR vaccine (or its components/preservatives like Thimerosal) and the development of Autism Spectrum Disorder (ASD). **Analysis of Options:** * **Option B (Autism):** Correct. This remains a high-yield topic in exams due to its impact on public health and vaccine hesitancy. * **Option A (ADHD):** While ADHD is a common neurodevelopmental disorder, there has never been a widely publicized or scientific hypothesis linking it specifically to the MMR vaccine. * **Option C (Dyslexia):** This is a specific learning disability related to reading and language processing, primarily linked to genetics and brain structure, not immunizations. * **Option D (Schizophrenia):** This is a psychiatric disorder typically manifesting in late adolescence or early adulthood; its etiology is multifactorial (genetic and environmental) but unrelated to childhood vaccinations. **Clinical Pearls for NEET-PG:** * **MMR Schedule:** 1st dose at 9–12 months, 2nd dose at 16–24 months (under National Immunization Schedule in India). * **Vaccine Type:** Live attenuated. * **Contraindications:** Pregnancy, severe immunosuppression (e.g., low CD4 counts), and history of anaphylaxis to neomycin or gelatin. * **Fact:** The "Thimerosal" scare (a mercury-based preservative) also focused on Autism, but MMR vaccines in single-dose vials have never actually contained Thimerosal.

Q: Which of the following diseases is NOT typically prevented by maternal antibodies?

Whooping cough. **Explanation:** The correct answer is **Whooping Cough (Pertussis)**. The underlying medical concept is the efficiency of **transplacental transfer of IgG antibodies**. While maternal antibodies (passive immunity) provide significant protection to newborns against many viral and bacterial toxins, this protection is notably absent or insufficient for Pertussis. 1. **Why Whooping Cough is correct:** Maternal antibodies against *Bordetella pertussis* are generally low in concentration and do not cross the placenta in sufficient quantities to provide effective immunity to the neonate. Consequently, infants are highly susceptible to pertussis from birth until they complete their primary immunization series (starting at 6 weeks). This is why the WHO and many national guidelines now recommend **Tdap vaccination during pregnancy** (ideally between 27–36 weeks) to boost maternal titers and maximize antibody transfer. 2. **Why other options are incorrect:** * **Polio:** Maternal IgG provides significant protection against paralytic poliomyelitis for the first few months of life. * **Diphtheria & Tetanus:** These are toxoid-mediated diseases. High levels of maternal antitoxins (IgG) are efficiently transferred across the placenta, protecting the newborn. This is the physiological basis for vaccinating pregnant women with Tetanus Toxoid (TT/Td) to prevent **Neonatal Tetanus**. **NEET-PG High-Yield Pearls:** * **Measles:** Maternal antibodies are so effective that they can interfere with live vaccines; hence, the Measles/MR vaccine is delayed until **9 months** of age. * **Passive Immunity:** Only **IgG** crosses the placenta. IgA is provided via colostrum/breast milk (local mucosal immunity). * **Pertussis:** It is the most common vaccine-preventable disease in children under 2 months of age due to this lack of natural maternal protection.

Q: Which of the following is NOT a cholera vaccine?

Ty21a. **Explanation:** The correct answer is **A. Ty21a**. This is because Ty21a is a live-attenuated **oral typhoid vaccine**, not a cholera vaccine. It is derived from the *Salmonella typhi* Ty2 strain and is administered as enteric-coated capsules. **Analysis of Options:** * **CVD-103-HgR (Vaxchora):** This is a live-attenuated, single-dose oral cholera vaccine derived from the *Vibrio cholerae* O1 classical Inaba strain. It is primarily used for travelers. * **WC-rBS (Dukoral):** This is a killed whole-cell (*V. cholerae* O1) vaccine combined with a recombinant B-subunit of the cholera toxin. It provides short-term protection and some cross-protection against Enterotoxigenic *E. coli* (ETEC). * **mORC-Vax:** This is a modified killed whole-cell oral cholera vaccine (containing O1 and O139 strains) produced in Vietnam. It is a precursor to the WHO-prequalified **Shanchol** vaccine used in India. **High-Yield Clinical Pearls for NEET-PG:** * **Oral Cholera Vaccines (OCVs):** Currently, the WHO prequalifies three OCVs: **Dukoral, Shanchol, and Euvichol-Plus**. * **Shanchol vs. Dukoral:** Unlike Dukoral, Shanchol does not require a buffer or water for administration and contains the O139 serogroup. * **Herd Immunity:** OCVs are known to provide significant herd protection in endemic settings. * **Injectable Vaccine:** The old parenteral killed whole-cell cholera vaccine is no longer recommended by the WHO due to low efficacy and short duration of protection.

Q: Which vaccine is most sensitive to heat?

OPV. **Explanation:** The correct answer is **OPV (Oral Polio Vaccine)**. **1. Why OPV is the correct answer:** The stability of vaccines is highly dependent on temperature. OPV is a live-attenuated virus vaccine that is extremely thermolabile. It is the **most heat-sensitive vaccine** in the entire Universal Immunization Programme (UIP). To maintain its potency, it must be stored at sub-zero temperatures (–20°C) for long-term storage and between +2°C to +8°C for short-term use. Because of its extreme sensitivity, the **Vaccine Vial Monitor (VVM)** was first introduced specifically for OPV to track heat exposure. **2. Why other options are incorrect:** * **Measles:** While Measles is also a live-attenuated vaccine and is heat-sensitive, it is more stable than OPV. It ranks second in the hierarchy of heat sensitivity. * **DPT & Hepatitis B:** These are **heat-stable** but **freeze-sensitive** vaccines. They lose their potency if frozen (the "Shake Test" is used to check for damage). Among all vaccines, **TT (Tetanus Toxoid)** is the most heat-stable. **3. High-Yield Clinical Pearls for NEET-PG:** * **Hierarchy of Heat Sensitivity (Most to Least):** OPV > Measles > BCG > DPT > DT > TT. * **Hierarchy of Freeze Sensitivity (Most to Least):** Hepatitis B > DPT > TT. * **Storage:** At the Health Center level (ILR), all vaccines (including OPV and Measles) are stored at **+2°C to +8°C**. Only at District levels and above is OPV stored at –20°C. * **The "Shake Test":** Used for DPT, Hepatitis B, and TT to identify damage caused by accidental freezing (never perform this on OPV or Measles).

Q: Booster dose of Tetanus toxoid should be given every?

5 years. **Explanation:** The correct answer is **5 years**. This recommendation is based on the duration of protective immunity provided by the Tetanus Toxoid (TT) vaccine. **1. Why 5 years is correct:** According to the National Immunization Schedule (NIS) and standard public health guidelines, after the primary series and initial boosters (at 16–24 months and 5–6 years), a booster dose is recommended every **5 years** to maintain an adequate titer of antibodies. In the context of injury management, if a person has completed their primary immunization but the last dose was more than 5 years ago, a booster is indicated for tetanus-prone wounds. **2. Analysis of Incorrect Options:** * **1 year (Option A):** Too frequent. Repeated doses of TT at very short intervals can lead to hypersensitivity reactions (Arthus-type) due to high circulating antibody levels. * **10 years (Option C):** While some international bodies (like the CDC) recommend a 10-year interval for healthy adults, Indian national guidelines and standard Community Medicine textbooks (like Park) emphasize the **5-year interval** for maintaining optimal community-level protection. * **15 years (Option D):** Too long. Antibody levels typically fall below protective thresholds (0.01 IU/ml) well before 15 years in a significant portion of the population. **3. High-Yield Clinical Pearls for NEET-PG:** * **Pregnancy:** Two doses of Tetanus-Diphtheria (Td) are given 4 weeks apart. If a woman was vaccinated within the last **3 years**, only one **Booster dose** is required. * **Injury Management:** If the last dose was 10 years ago, give both TT and Tetanus Immunoglobulin (TIG) for category B/C wounds. * **Replacement:** TT is now being replaced by the **Td (Tetanus and adult Diphtheria)** vaccine in the Universal Immunization Programme to provide additional protection against Diphtheria.

Q: What is the adjuvant used in the DPT vaccine?

Aluminium. The correct answer is **Aluminium (Option B)**. ### **Explanation** The DPT (Diphtheria, Pertussis, and Tetanus) vaccine is an inactivated vaccine that utilizes **Aluminium salts** (commonly Aluminium hydroxide or Aluminium phosphate) as an **adjuvant**. **The Medical Concept:** An adjuvant is a substance added to a vaccine to enhance the body's immune response to an antigen. Aluminium salts work through the **"Depot Effect"**—they trap the vaccine antigens at the injection site, ensuring a slow and sustained release. This prolonged exposure allows antigen-presenting cells (APCs) more time to process the antigen, leading to a more robust production of antibodies and longer-lasting immunity. ### **Analysis of Incorrect Options** * **A. Zinc:** While Zinc is vital for general immune function and used in ORS for diarrhea management, it has no role as a vaccine adjuvant. * **C. Copper:** Copper is an essential trace element but is not used in vaccine formulations; it is more commonly associated with Wilson’s disease or intrauterine devices (Cu-T). * **D. Magnesium:** Magnesium is a cofactor for many enzymatic reactions but does not possess the immunological properties required to act as an adjuvant. ### **High-Yield Clinical Pearls for NEET-PG** * **Route of Administration:** Because DPT contains an aluminium adjuvant, it **must** be given via **Deep Intramuscular (IM)** injection. If given subcutaneously, the aluminium can cause local irritation, granulomas, or "sterile abscesses." * **The Shake Test:** Vaccines with aluminium adjuvants (DPT, TT, Hep B) are **freeze-sensitive**. If frozen, the aluminium lattice structure breaks, and the vaccine loses potency. The "Shake Test" is used to identify if a vaccine has been damaged by freezing. * **Other Adjuvants:** While Aluminium is the most common, others include **MF59** (oil-in-water emulsion) and **AS04** (used in HPV vaccines).

Question 1

Which of the following is NOT a criterion for measles elimination?

Accepted Answer

Sporadic imported cases are permitted

Answer

Absence of endemic measles transmission

Answer

Documentation of no indigenous cases for more than 12 months

Answer

Incidence of less than 1 case per 100,000 population per year

Question 2

The MMR vaccine is controversially associated with which of the following conditions?

Accepted Answer

Autism

Answer

Attention-Deficit/Hyperactivity Disorder (ADHD)

Answer

Dyslexia

Answer

Schizophrenia

Question 3

Which of the following diseases is NOT typically prevented by maternal antibodies?

Accepted Answer

Whooping cough

Answer

Polio

Answer

Diphtheria

Answer

Tetanus

Question 4

Which of the following is NOT a cholera vaccine?

Accepted Answer

Ty21a

Answer

CVD-103-HgR

Answer

WC-rBS

Answer

mORC-Vax

Question 5

Which of the following is NOT true regarding acute flaccid paralysis surveillance in the National Polio Eradication Programme?

Accepted Answer

A 30-day follow-up examination is required for all reported cases.

Answer

Acute flaccid paralysis is defined in a child less than 15 years of age.

Answer

All cases of AFP should be reported irrespective of diagnosis, within 6 weeks of onset of stool.

Answer

Two stool specimens should be collected within 14 days of paralysis onset and at least 24 hours apart.

Question 6

Which vaccine is most sensitive to heat?

Accepted Answer

OPV

Answer

Measles

Answer

Hepatitis B

Answer

DPT

Question 7

Which of the following is NOT a true statement regarding the Haemophilus influenzae type b (Hib) vaccine?

Accepted Answer

It protects against non-encapsulated strains of Haemophilus influenzae.

Answer

Catch-up vaccination is recommended before the age of 5 years.

Answer

It can be administered to infants less than 6 months of age.

Answer

It should be given at least 2 weeks prior to splenectomy.

Question 8

Which of the following statements regarding vaccine reconstitution is FALSE?

Accepted Answer

JE vaccine is reconstituted with sterile water.

Answer

Yellow fever vaccine is reconstituted with cold physiological saline.

Answer

Measles vaccine is reconstituted with distilled water.

Answer

BCG vaccine is reconstituted with normal saline.

Question 9

Booster dose of Tetanus toxoid should be given every?

Accepted Answer

5 years

Answer

1 year

Answer

10 years

Answer

15 years

Question 10

What is the adjuvant used in the DPT vaccine?

Accepted Answer

Aluminium

Answer

Zinc

Answer

Copper

Answer

Magnesium

Immunization and Vaccine-Preventable Diseases — MCQs

Immunization and Vaccine-Preventable Diseases — MCQs

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