Immunization and Vaccine-Preventable Diseases Practice Questions

Q: After vaccination against Japanese encephalitis, when does immunity typically develop?

30 days. **Explanation:** The development of protective immunity following Japanese Encephalitis (JE) vaccination is a gradual process. In the context of the **live attenuated SA 14-14-2 vaccine** (the strain most commonly used in the Universal Immunization Programme in India), protective antibodies typically reach significant levels approximately **one month (30 days)** after the administration of a single dose. **Why 30 days is correct:** Immunological studies indicate that while seroconversion begins earlier, the peak primary immune response and the establishment of robust, protective neutralizing antibody titers (PRNT titers ≥1:10) generally stabilize around the 30-day mark. This duration allows for the necessary viral replication of the attenuated strain and subsequent B-cell activation and maturation. **Analysis of incorrect options:** * **7 and 10 days:** These timeframes are too short for a primary immune response to generate sufficient IgG titers for neurotropic viruses like JE. At this stage, the body is primarily in the innate and early IgM phase. * **21 days:** While some individuals may show immunity by three weeks, 30 days is the standard clinical benchmark used in public health guidelines and textbooks (like Park’s PSM) to ensure reliable protection. **High-Yield Clinical Pearls for NEET-PG:** * **Vaccine Strain:** The SA 14-14-2 is a live attenuated vaccine derived from primary hamster kidney cells. * **Schedule (UIP):** Two doses are given under the Universal Immunization Programme—the 1st dose at **9 months** (with Measles/MR) and the 2nd dose at **16–24 months** (with DPT booster). * **Route:** Subcutaneous (0.5 ml). * **Vector:** Transmitted by the **Culex tritaeniorhynchus** mosquito, which breeds in stagnant water (paddy fields). * **Reservoir:** Pigs (amplifier host) and Ardeid birds (natural reservoir). Humans are **dead-end hosts**.

Q: Which of the following vaccinations is absolutely contraindicated in pregnancy?

Yellow fever. **Explanation:** The core principle in obstetric immunization is that **Live Attenuated Vaccines** are generally contraindicated during pregnancy due to the theoretical risk of the vaccine virus crossing the placenta and causing fetal infection. **Yellow Fever (Option D)** is a live attenuated viral vaccine. It is absolutely contraindicated in pregnancy because of the potential risk of vertical transmission and fetal harm. It should only be considered in high-risk scenarios where travel to an endemic area is unavoidable and the risk of the disease outweighs the risk of vaccination. **Analysis of Incorrect Options:** * **Hepatitis B (Option A):** This is a **subunit (recombinant)** vaccine. It contains no live virus and is safe and recommended for pregnant women at high risk of infection. * **Cholera (Option B):** Modern cholera vaccines are **killed/inactivated** (oral or injectable). Inactivated vaccines are generally considered safe during pregnancy if the risk of exposure is high. * **Rabies (Option C):** This is an **inactivated** vaccine. Because rabies is 100% fatal, pregnancy is never a contraindication for post-exposure prophylaxis. It is safe for both mother and fetus. **High-Yield NEET-PG Pearls:** 1. **Live Vaccines Contraindicated:** Remember the mnemonic **"Rome Is My Very Best Vacation"** (Rubella, Oral Polio, Measles, Mumps, Varicella, BCG, Yellow Fever). 2. **Exception:** If a pregnant woman is traveling to a high-risk Yellow Fever zone, the vaccine may be given under strict medical supervision, but it remains the "most contraindicated" among the options provided. 3. **Safe Vaccines:** Tetanus, Diphtheria, and Pertussis (Tdap) are not only safe but routinely recommended during pregnancy (usually between 27–36 weeks) to provide passive immunity to the newborn.

Q: Who was the pioneer in the concept of specific protection by vaccine?

Chinese. **Explanation:** The concept of **Specific Protection** refers to measures taken to prevent the occurrence of a specific disease. The historical pioneer of this concept is the **Chinese**, who practiced **Variolation** as early as the 10th century. This involved the deliberate inoculation of material from smallpox pustules (via inhalation or skin scratching) into healthy individuals to induce a mild form of the disease, thereby granting lifelong immunity. This predates Edward Jenner’s cowpox vaccine (1796) by centuries. **Analysis of Options:** * **Chinese (Correct):** Credited with the earliest form of immunization (variolation) against smallpox, establishing the foundation for specific protection. * **Robert Koch:** Known as the "Father of Bacteriology." He discovered the causative agents of Anthrax, Cholera, and Tuberculosis (Koch’s Postulates) but was not the pioneer of vaccination. * **Ambroise Paré:** A French surgeon considered the "Father of Modern Surgery." He revolutionized the treatment of wounds but had no role in the development of vaccines. * **Louis Pasteur:** Known as the "Father of Microbiology." While he developed vaccines for Anthrax and Rabies and coined the term "Vaccine" (in honor of Jenner), he was not the first to practice the concept of specific protection. **NEET-PG High-Yield Pearls:** * **Levels of Prevention:** Specific protection is a component of **Primary Prevention**. * **Edward Jenner:** Performed the first scientific vaccination (using cowpox for smallpox) in 1796. * **Louis Pasteur:** Developed the first **live attenuated vaccines**. * **Smallpox:** The only human disease to be globally eradicated (declared by WHO on May 8, 1980).

Q: All of the following are true of the BCG vaccine except:

Administered subcutaneously. **Explanation:** The BCG (Bacillus Calmette-Guérin) vaccine is a **live attenuated vaccine** derived from *Mycobacterium bovis*. The correct answer is **B** because BCG is strictly administered via the **intradermal route**, not subcutaneously. 1. **Why Option B is correct (The Exception):** BCG must be given intradermally (usually over the left deltoid) using an insulin or tuberculin syringe (26G). If injected subcutaneously, it can lead to severe local complications such as abscess formation or regional lymphadenitis. 2. **Why other options are incorrect:** * **Option A:** The standard dose for infants over 4 weeks of age is **0.1 ml**. (Note: For neonates below 4 weeks, the dose is 0.05 ml to prevent excessive scarring). * **Option C:** The **Danish 1331 strain** is the most commonly used strain globally and in India for vaccine production. * **Option D:** BCG is a classic example of a **live attenuated bacterial vaccine**. **High-Yield Clinical Pearls for NEET-PG:** * **Diluent:** Normal Saline (NS) is used. Distilled water is avoided as it causes irritation. * **Storage:** It is heat-sensitive and light-sensitive; supplied in dark-colored ampoules and must be used within 4–6 hours of reconstitution. * **Phenomenon:** A papule forms at 2–3 weeks, followed by a crust/ulcer at 5–6 weeks, eventually leaving a permanent **pitted scar** by 6–12 weeks. * **Protective Effect:** It provides high protection against disseminated forms (Miliary TB and TB Meningitis) but has variable efficacy (0–80%) against adult pulmonary TB.

Q: What is the ideal recommended time for observation following immunization for adverse events following immunization (AEFI)?

30 minutes. **Explanation:** The correct answer is **30 minutes (Option B)**. **1. Why it is correct:** The primary purpose of post-vaccination observation is the early detection and management of immediate **anaphylactic reactions**. Anaphylaxis is a life-threatening, Type-I hypersensitivity reaction that typically occurs within minutes of exposure to an allergen. According to the **Universal Immunization Programme (UIP)** and **WHO guidelines**, every vaccine recipient must be observed for at least 30 minutes at the session site. This "waiting period" ensures that if a severe allergic reaction occurs, trained healthcare personnel can intervene immediately with Adrenaline (1:1000). **2. Why other options are incorrect:** * **15 minutes (Option A):** While some mild reactions occur early, 15 minutes is insufficient to capture the majority of immediate-onset anaphylactic events. * **45 minutes & 1 hour (Options C & D):** While longer observation is safer, it is logistically impractical for mass immunization campaigns and routine clinics. 30 minutes is the established gold standard that balances safety with public health efficiency. **3. High-Yield Clinical Pearls for NEET-PG:** * **Drug of Choice for Anaphylaxis:** Adrenaline (Epinephrine) 1:1000 concentration, administered **Intramuscularly (IM)** in the anterolateral aspect of the thigh. * **AEFI Surveillance:** AEFI is defined as any untoward medical occurrence following immunization, which does not necessarily have a causal relationship with the vaccine. * **Cold Chain:** Most UIP vaccines are stored between **+2°C to +8°C**. * **Most Heat Sensitive Vaccine:** Oral Polio Vaccine (OPV). * **Most Freeze Sensitive Vaccine:** Hepatitis B and DPT/Pentavalent.

Q: Thrombocytopenia is an adverse reaction of which vaccine?

MMR. **Explanation:** The correct answer is **MMR (Measles, Mumps, and Rubella)**. **Why MMR is the correct answer:** Immune Thrombocytopenic Purpura (ITP) is a recognized, though rare, adverse event following immunization (AEFI) specifically associated with the **Measles** component of the MMR vaccine. The underlying mechanism is believed to be **molecular mimicry**, where vaccine-induced antibodies cross-react with surface antigens on the patient’s platelets, leading to their destruction in the spleen. This typically occurs within 6 weeks of vaccination and is usually self-limiting. **Why other options are incorrect:** * **BCG:** Common adverse effects include local lymphadenitis and cold abscesses. It is not associated with platelet disorders. * **DPT:** Known for local reactions (pain, swelling) and systemic reactions like fever or persistent crying. The Pertussis component is rarely linked to encephalopathy, but not thrombocytopenia. * **Hep B:** The most significant (though rare) serious adverse effect is anaphylaxis. It is also occasionally linked to hypersensitivity reactions, but thrombocytopenia is not a characteristic feature. **High-Yield Clinical Pearls for NEET-PG:** * **Risk Ratio:** The risk of thrombocytopenia after MMR vaccination is approximately 1 in 30,000 doses—significantly lower than the risk of thrombocytopenia following a natural Measles or Rubella infection. * **Other MMR Side Effects:** Febrile seizures (due to the Measles component) and transient arthralgia (due to the Rubella component). * **Contraindication:** MMR is a **Live Attenuated Vaccine** and is contraindicated in pregnancy and severely immunocompromised individuals. * **Storage:** MMR is highly heat-sensitive and must be stored at +2°C to +8°C, protected from light.

Question 1

After vaccination against Japanese encephalitis, when does immunity typically develop?

Accepted Answer

30 days

Answer

7 days

Answer

10 days

Answer

21 days

Question 2

Which of the following vaccinations is absolutely contraindicated in pregnancy?

Accepted Answer

Yellow fever

Answer

Hepatitis-B

Answer

Cholera

Answer

Rabies

Question 3

Who was the pioneer in the concept of specific protection by vaccine?

Accepted Answer

Chinese

Answer

Robert Koch

Answer

Ambroise Paré

Answer

Louis Pasteur

Question 4

All of the following are true of the BCG vaccine except:

Accepted Answer

Administered subcutaneously

Answer

Dose is 0.1 ml

Answer

Uses the Danish 1331 strain

Answer

It is a live attenuated vaccine

Question 5

What is the ideal recommended time for observation following immunization for adverse events following immunization (AEFI)?

Accepted Answer

30 minutes

Answer

15 minutes

Answer

45 minutes

Answer

1 hour

Question 6

Which of the following vaccines is not given to an unimmunized 8-year-old male child?

Accepted Answer

Acellular pertussis vaccine

Answer

Inactivated polio vaccine

Answer

Hepatitis B vaccine

Answer

Measles vaccine

Question 7

Reverse Cold Chain is used for what purpose?

Accepted Answer

Transportation of poliomyelitis stool samples from the field to the laboratory

Answer

Transportation of vaccines at +2 to +8 degrees Celsius from PHC to sub-centre

Answer

Transportation of Oral Polio vaccine at -20 to -40 degrees Celsius

Answer

None of the above

Question 8

Thrombocytopenia is an adverse reaction of which vaccine?

Accepted Answer

MMR

Answer

BCG

Answer

DPT

Answer

Hep B

Question 9

A resident sustains a needle-stick injury from a patient positive for HBsAg and HBeAg who is not immunized. What is the appropriate management?

Accepted Answer

Combined active and passive immunization

Answer

No intervention needed

Answer

Active immunization only

Answer

Passive immunization only

Question 10

Toxic shock syndrome is mostly associated with which vaccine?

Accepted Answer

Measles

Answer

Mumps

Answer

Salk

Answer

Tetanus

Immunization and Vaccine-Preventable Diseases — MCQs

Immunization and Vaccine-Preventable Diseases — MCQs

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