Immunization and Vaccine-Preventable Diseases Practice Questions

Q: Which anti-rabies vaccine has been recommended by WHO?

HDCV. **Explanation:** The World Health Organization (WHO) recommends the use of **Modern Cell Culture Vaccines (CCVs)** and **Embryonated Egg-based Vaccines (EEVs)** for both pre-exposure and post-exposure prophylaxis. Among these, the **Human Diploid Cell Vaccine (HDCV)** is considered the "gold standard" due to its high immunogenicity and superior safety profile. **Analysis of Options:** * **HDCV (Correct):** Developed using the Pitman-Moore strain of the rabies virus grown in human diploid cells (MRC-5). It is highly effective and has the lowest rate of adverse neurological reactions. * **Ducek cell vaccine (Incorrect):** This is a distractor; there is no recognized rabies vaccine by this name. * **Chick fibroblast vaccine (Incorrect):** While Purified Chick Embryo Cell Vaccine (PCECV) is a WHO-recommended CCV, "Chick fibroblast vaccine" is an imprecise term. HDCV remains the primary reference vaccine. * **Sheep brain vaccine (Incorrect):** Also known as the **Semple vaccine**, this is a Nerve Tissue Vaccine (NTV). WHO has strictly advocated for the discontinuation of NTVs because they are less immunogenic and carry a high risk of severe neuroparalytic complications (e.g., Acute Disseminated Encephalomyelitis) due to the presence of myelin. **High-Yield Clinical Pearls for NEET-PG:** * **Current WHO Schedule (Intramuscular):** The Essen regimen (0, 3, 7, 14, and 28 days). * **Current WHO Schedule (Intradermal):** The updated Thai Red Cross regimen (2-2-2-0-2) is widely used in India for cost-effectiveness. * **Site of Injection:** Always the **deltoid muscle** in adults or the anterolateral thigh in children. **Never** in the gluteal region (lower neutralizing antibody titers). * **Category III Bites:** Require both vaccine and Rabies Immunoglobulin (RIG) infiltrated around the wound.

Q: Duration of immunity after typhoid vaccination is for?

3 years. **Explanation:** The duration of immunity for typhoid vaccines depends on the type of vaccine administered. For the most commonly used vaccines in public health programs—the **Vi polysaccharide vaccine** (injectable) and the **Ty21a vaccine** (oral)—the protective efficacy lasts for approximately **3 years**. 1. **Why 3 years is correct:** * **Vi Polysaccharide Vaccine:** Administered as a single subcutaneous or intramuscular dose. It provides about 70% protection, which wanes significantly after 3 years, necessitating a booster dose every 3 years. * **Ty21a (Live Attenuated) Vaccine:** Administered orally (3-4 doses). It provides comparable protection for 3 years, though some studies suggest slightly longer persistence in endemic areas due to natural boosting. 2. **Why other options are incorrect:** * **5-7 years:** While newer **Typhoid Conjugate Vaccines (TCV)**, like the PedaTyph or Typbar-TCV, show promise for longer-lasting immunity (potentially up to 5 years or more) and are recommended for infants, the standard benchmark for traditional vaccines remains 3 years. * **6 months:** This is too short for typhoid vaccines. This duration is more characteristic of the older, now-obsolete parenteral whole-cell killed vaccines which had high reactogenicity and short-lived protection. **High-Yield NEET-PG Pearls:** * **Typhoid Conjugate Vaccine (TCV):** The only typhoid vaccine licensed for children as young as **6 months** of age. It provides superior immunogenicity. * **Vi Vaccine Age:** Cannot be given to children **<2 years** (poor T-cell independent response). * **Ty21a Age:** Not recommended for children **<6 years**. * **Control Measure:** The most effective method for long-term typhoid control remains the improvement of sanitation and water supply, not just vaccination.

Q: Meningococcal vaccines should be stored at what temperature range?

2-8 °C. ### Explanation **Correct Answer: C. 2-8 °C** **Underlying Medical Concept:** Most vaccines used in the Universal Immunization Programme (UIP) and clinical practice are thermolabile and require a strict "Cold Chain" to maintain potency. Meningococcal vaccines (both polysaccharide and conjugate versions) are **heat-sensitive** but, more importantly, **freeze-sensitive**. They must be stored in the refrigerator compartment (2-8 °C) and never in the freezer. Freezing can cause the antigen to precipitate or damage the adjuvant, leading to a loss of immunogenicity and potential increase in local adverse reactions. **Analysis of Incorrect Options:** * **A (-4 °C) & D (-20 °C):** These temperatures are below freezing. Storing Meningococcal vaccines here would lead to irreversible damage. Sub-zero temperatures (specifically -20 °C) are reserved for highly heat-sensitive vaccines like **OPV** (Oral Polio Vaccine) and **Yellow Fever** vaccine. * **B (0 °C):** This is the freezing point of water. Maintaining a vaccine exactly at 0 °C carries a high risk of accidental freezing due to thermostat fluctuations, making it an unsafe storage target. **High-Yield Clinical Pearls for NEET-PG:** * **Freeze-Sensitive Vaccines:** Remember the mnemonic **"DPT-Hep-M"** (DPT, DT, TT, Hepatitis B, and Meningococcal/Hib). These must **never** be frozen. * **The Shake Test:** If you suspect a freeze-sensitive vaccine (like Meningococcal or DPT) has been frozen, perform the **Shake Test**. If the vaccine settles faster than a control vial, it has been damaged and must be discarded. * **Storage Level:** In an Ice-Lined Refrigerator (ILR), Meningococcal vaccines are stored in the **basket** (top/middle) to keep them away from the colder bottom surface. * **Most Heat Sensitive:** OPV. * **Least Heat Sensitive:** TT (Tetanus Toxoid).

Q: Which of the following statements regarding tetanus is true?

Tetanus has no period of communicability.. ### Explanation **1. Why Option A is Correct:** Tetanus is caused by the neurotoxin of *Clostridium tetani*. Unlike many infectious diseases, it is **not transmitted from person to person**. The bacteria enter the body through contaminated wounds (soil, street dust, or animal feces). Since there is no horizontal transmission between humans, it is said to have **no period of communicability**. **2. Why the Other Options are Incorrect:** * **Option B:** India was declared to have achieved **Maternal and Neonatal Tetanus Elimination (MNTE)** by the WHO in **May 2015** (officially July 2016), not 2010. Note that "elimination" in this context refers to <1 case per 1,000 live births in every district; tetanus can never be "eradicated" because the spores persist in the soil. * **Option C:** Neonatal tetanus is traditionally known as the **"8th-day disease"** because symptoms typically appear about a week after birth due to umbilical cord contamination. * **Option D:** Tetanus toxoid is not a live vaccine and does not provide lifelong immunity with a single dose. The primary schedule followed by periodic boosters (every 10 years) is required to maintain protective antibody levels. **3. High-Yield NEET-PG Pearls:** * **Incubation Period:** Typically 6–10 days. The shorter the incubation period, the worse the prognosis. * **Clinical Hallmark:** *Trismus* (lockjaw) is the most common presenting symptom, followed by *risus sardonicus* (facial spasms) and *opisthotonus* (backward arching). * **Herd Immunity:** Tetanus is the only vaccine-preventable disease where **herd immunity does not exist**, as the protection is purely individual. * **Type of Immunity:** Tetanus toxoid provides **active immunity**, while Tetanus Immunoglobulin (TIG) provides **passive immunity**.

Q: For how long can vaccines be stored at a Primary Health Centre (PHC)?

30 days. ### Explanation **Correct Answer: D. 30 days** In the Indian Universal Immunization Programme (UIP) cold chain system, the duration of vaccine storage is determined by the level of the healthcare facility. A **Primary Health Centre (PHC)** is equipped with an **Ice-Lined Refrigerator (ILR)** and a Deep Freezer (small). According to standard guidelines, vaccines can be stored at the PHC level for a maximum of **one month (30 days)**. This duration ensures a balance between maintaining vaccine potency and managing supply logistics from the district level. **Analysis of Incorrect Options:** * **A & B (2 days / 7 days):** These durations are too short for a PHC. However, 48–72 hours is the typical duration vaccines are kept in **vaccine carriers** during outreach sessions or "sub-centre" activities. * **C (15 days):** While some regional guidelines previously suggested shorter intervals, the standard UIP protocol for PHCs remains 30 days. 15 days is not a standard benchmark for any specific level of the cold chain. **High-Yield Clinical Pearls for NEET-PG:** * **Storage Levels & Durations:** * **Regional/State Level (GMSD):** 3 months. * **District Level:** 1 month. * **PHC Level:** 1 month. * **Sub-centre/Session Site:** 48–72 hours (in vaccine carriers). * **Temperature Maintenance:** At the PHC, ILRs maintain a temperature of **+2°C to +8°C**, which is ideal for most vaccines (including Tseries, HepB, and DPT). * **The "Shake Test":** Used to determine if a freeze-sensitive vaccine (like DPT, TT, or Pentavalent) has been damaged by sub-zero temperatures. * **Most Heat Sensitive Vaccine:** Oral Polio Vaccine (OPV). * **Most Heat Resistant Vaccine:** Tetanus Toxoid (TT).

Q: Bivalent oral polio vaccine contains which strains of poliovirus?

1 and 3. **Explanation:** The correct answer is **C (1 and 3)**. The **Bivalent Oral Polio Vaccine (bOPV)** was introduced globally as part of the "Polio Endgame Strategy" following the eradication of Wild Poliovirus Type 2 (WPV2), which was last detected in 1999 and declared eradicated in 2015. 1. **Why Option C is correct:** bOPV contains live-attenuated Sabin strains of **Poliovirus Type 1 and Type 3**. Since Type 2 was eradicated, its inclusion in the oral vaccine was discontinued to prevent cases of Vaccine-Derived Poliovirus Type 2 (VDPV2) and Vaccine-Associated Paralytic Polio (VAPP). 2. **Why Options A, B, and D are incorrect:** * **Option A & B:** These include Type 2. The switch from Trivalent OPV (tOPV, containing 1, 2, and 3) to bOPV occurred in April 2016. Type 2 is now only covered via the **Inactivated Polio Vaccine (IPV)** to maintain immunity without the risk of shedding live virus. * **Option D:** There are only three known serotypes of poliovirus (1, 2, and 3); Type 4 does not exist. **High-Yield Clinical Pearls for NEET-PG:** * **The Switch:** India switched from tOPV to bOPV on **April 25, 2016**. * **WPV Status:** Type 2 (1999) and Type 3 (2012) have been eradicated globally. Only Type 1 remains endemic (primarily in Afghanistan and Pakistan). * **VAPP vs. VDPV:** VAPP is a rare adverse event in the vaccine recipient; VDPV occurs due to prolonged circulation of the vaccine virus in under-immunized communities. Type 2 was responsible for >90% of VDPV cases. * **Current Schedule (Universal Immunization Programme):** bOPV at 6, 10, and 14 weeks (plus booster at 16-24 months) and Fractional IPV (fIPV) at 6 and 14 weeks (intradermal).

Q: If convulsions are present, which vaccine should not be administered?

DPT. **Explanation:** The correct answer is **DPT (Diphtheria, Pertussis, and Tetanus)**. The primary reason for this contraindication is the **Whole-cell Pertussis (wP)** component of the vaccine. Pertussis antigens are known to be neurotoxic and can trigger neurological complications, including febrile seizures, encephalopathy, or prolonged convulsions. **Why DPT is the correct answer:** In clinical practice, a history of uncontrolled seizures, progressive neurological disorders, or an evolving neurological condition is a **strict contraindication** for the pertussis component. If a child has a history of convulsions, the "Triple Vaccine" (DPT) is withheld and replaced with **DT (Diphtheria and Tetanus)** to avoid aggravating the neurological state. **Why other options are incorrect:** * **Oral Polio (OPV):** This is a live attenuated vaccine. Its primary contraindications are immunodeficiency states (e.g., HIV, hypogammaglobulinemia) or household contact with an immunocompromised person. It has no association with convulsions. * **BCG:** This is contraindicated in individuals with generalized eczema, skin infections at the site of injection, or severe immunodeficiency. It does not affect the central nervous system. * **Tetanus Toxoid (TT):** TT is generally safe. It is the pertussis component in the DPT combination that is the culprit, not the tetanus component. **High-Yield Clinical Pearls for NEET-PG:** * **Absolute Contraindication for Pertussis:** Encephalopathy within 7 days of a previous dose. * **Alternative:** In children with a history of seizures where pertussis coverage is still desired, **acellular Pertussis (aP)** is preferred over whole-cell (wP) as it has a significantly lower risk of febrile seizures. * **DT vs. DPT:** If a child is over 7 years old or has neurological contraindications, the Pertussis component is dropped, and DT/Td is administered.

Q: All of the following statements regarding the Salk vaccine are true EXCEPT:

OPV cannot be given as a booster dose.. **Explanation:** The **Salk vaccine (Inactivated Poliovirus Vaccine - IPV)** is a killed vaccine administered parenterally. The question asks for the "Except" statement, making Option A the correct answer because it is a **false** statement. **1. Why Option A is the correct answer (False statement):** OPV **can** be given as a booster dose even if the primary immunization was done with IPV. In fact, the current National Immunization Schedule (NIS) in India utilizes a sequential schedule or fractional IPV (fIPV) alongside OPV to provide both systemic and mucosal immunity. Using OPV as a booster helps provide intestinal immunity which IPV lacks. **2. Analysis of Incorrect Options (True statements regarding IPV):** * **Option B:** Injections (including IPV) during a polio epidemic can trigger **"Provocative Paralysis"** in a child already incubating the wild poliovirus. This is why routine intramuscular injections are often discouraged during active outbreaks. * **Option C:** Since IPV is an injectable killed vaccine, it induces high titers of **circulating IgG antibodies** (humoral immunity) but fails to induce significant **Secretory IgA** in the gut (local immunity). * **Option D:** Because IPV lacks local gut immunity, it **does not prevent the multiplication** of the wild virus in the intestinal tract. Consequently, an IPV-vaccinated individual can still shed the virus in feces and contribute to community transmission. **High-Yield NEET-PG Pearls:** * **Sabin (OPV):** Live attenuated; induces both systemic (IgG) and local (IgA) immunity; prevents subclinical infection; risk of VAPP/VDPV. * **Salk (IPV):** Killed; induces only systemic (IgG) immunity; safer (no risk of VAPP); does not stop community spread. * **Current Schedule:** India uses **fractional IPV (0.1 ml, intradermal)** at 6, 14 weeks, and 9 months of age.

Question 1

Which anti-rabies vaccine has been recommended by WHO?

Accepted Answer

HDCV

Answer

Ducek cell vaccine

Answer

Chick fibroblast vaccine

Answer

Sheep brain vaccine

Question 2

What is true about the Oral Polio Vaccine?

Accepted Answer

Causes poliomyelitis in recipients

Answer

Causes poliomyelitis in contacts of non-recipients

Answer

Causes Guillain-barre syndrome

Answer

Causes vomiting and fever

Question 3

A 5-year-old boy presents with a bleeding wound from a bite by his pet dog, which was fully vaccinated. He previously completed anti-rabies immunization in December 2018. What post-exposure prophylaxis against rabies is recommended for this patient?

Accepted Answer

Single site, 2 doses on day 0 and 3

Answer

No anti-rabies vaccine required

Answer

Single site, 4 doses on day 0, 3, 7, and 28

Answer

Rabies immunoglobulin and 4 doses of vaccine

Question 4

Duration of immunity after typhoid vaccination is for?

Accepted Answer

3 years

Answer

5 years

Answer

7 years

Answer

6 months

Question 5

Meningococcal vaccines should be stored at what temperature range?

Accepted Answer

2-8 °C

Answer

-4 °C

Answer

0 °C

Answer

-20 °C

Question 6

Which of the following statements regarding tetanus is true?

Accepted Answer

Tetanus has no period of communicability.

Answer

Tetanus was eliminated from India in 2010.

Answer

Tetanus is also known as 'second day disease'.

Answer

A single dose of tetanus toxoid provides lifelong immunity.

Question 7

For how long can vaccines be stored at a Primary Health Centre (PHC)?

Accepted Answer

30 days

Answer

2 days

Answer

7 days

Answer

15 days

Question 8

Bivalent oral polio vaccine contains which strains of poliovirus?

Accepted Answer

1 and 3

Answer

1, 8c, 2

Answer

2 and 3

Answer

3 and 4

Question 9

If convulsions are present, which vaccine should not be administered?

Accepted Answer

DPT

Answer

Oral Polio

Answer

BCG

Answer

Tetanus toxoid

Question 10

All of the following statements regarding the Salk vaccine are true EXCEPT:

Accepted Answer

OPV cannot be given as a booster dose.

Answer

Injections during an epidemic can cause paralysis.

Answer

It induces circulating antibody but no local immunity.

Answer

It does not prevent multiplication of wild virus in the gut.

Immunization and Vaccine-Preventable Diseases — MCQs

Immunization and Vaccine-Preventable Diseases — MCQs

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