Immunization and Vaccine-Preventable Diseases Practice Questions

Q: What does the sticker shown on a vaccine vial indicate?

Cold chain maintenance. ***Cold chain maintenance*** - The sticker is a **Vaccine Vial Monitor (VVM)** that uses heat-sensitive color changes to indicate if the vaccine has been exposed to excessive heat during storage or transport. - It provides a **cumulative heat exposure record** showing whether the **cold chain** has been maintained throughout the vaccine's journey from manufacturer to administration. *Efficacy* - Efficacy refers to how well a vaccine works in **controlled clinical trials** and is not indicated by any sticker on the vial. - This information is determined through **clinical studies** and documented in product literature, not visual indicators. *Expiry* - The **expiration date** is printed directly on the vaccine vial label as text, not indicated by a color-changing sticker. - VVM stickers complement but do not replace **expiry date information** which shows when the vaccine should no longer be used. *Viability* - Viability refers to whether vaccine components are **biologically active** and cannot be determined by external visual indicators alone. - This requires **laboratory testing** and sterility assessments that are not reflected in sticker technology.

Q: Vaccines at a Primary Health Centre (PHC) are stored in which of the following?

Ice-lined refrigerator (ILR). **Explanation:** The **Ice-lined Refrigerator (ILR)** is the backbone of the cold chain at the Primary Health Centre (PHC) level. It is specifically designed to maintain a stable temperature between **+2°C to +8°C**, which is the ideal range for storing most vaccines, including heat-sensitive ones like BCG and Measles, and frost-sensitive ones like DPT and Hepatitis B. The "ice-lining" (tubes or panels filled with water) ensures that even during a power failure of up to 24 hours, the internal temperature remains within the safe range. **Analysis of Options:** * **Ice-lined Refrigerator (ILR):** Correct. It is the primary storage equipment at PHCs and District levels for keeping vaccines at the required +2°C to +8°C. * **Deep Freezer:** Incorrect. At the PHC level, deep freezers are primarily used for **preparing ice packs** and storing OPV (if required). Storing frost-sensitive vaccines (Tseries) here would lead to loss of potency. * **Ice Box:** Incorrect. These are used for the **transportation** of vaccines from the PHC to outreach sessions (sub-centers/villages) or during short-term emergencies, but not for long-term storage at the facility. **High-Yield Clinical Pearls for NEET-PG:** * **Cold Chain Levels:** Regional/District levels use Walk-in-Coolers (WIC); PHCs use ILRs; Sub-centers use Vaccine Carriers. * **Placement in ILR:** Heat-sensitive vaccines (OPV, Measles) are kept at the bottom (coolest part), while freeze-sensitive vaccines (TT, DPT, Hep B) are kept at the top to prevent freezing. * **Monitoring:** Temperature should be recorded **twice daily**. * **Shake Test:** Used to determine if a freeze-sensitive vaccine (like DPT) has been damaged by sub-zero temperatures.

Q: What is the efficacy of the BCG vaccine for pulmonary tuberculosis?

0%. **Explanation:** The efficacy of the BCG (Bacillus Calmette-Guérin) vaccine is one of the most debated topics in preventive medicine due to its wide variability across different geographical regions. In the context of **Pulmonary Tuberculosis (TB)**, particularly in adults and in countries like India, multiple trials (most notably the Chingleput trial) have shown that the protective efficacy of BCG is **0%**. **Why the correct answer is 0%:** While BCG is highly effective against severe childhood forms of TB (disseminated and meningeal TB), it provides little to no protection against the adult pulmonary form of the disease. Factors contributing to this 0% efficacy include interference by environmental mycobacteria, genetic variations in the vaccine strain, and the nature of the immune response required to prevent reactivation of latent TB. **Analysis of Incorrect Options:** * **Options B, C, and D (25%, 33%, 50%):** While some international studies have shown varying degrees of protection (ranging from 0 to 80%), for the purpose of standard medical examinations and based on the landmark Indian trials, the efficacy for pulmonary TB is specifically cited as zero. These percentages do not represent the established consensus for pulmonary protection in endemic regions. **High-Yield Clinical Pearls for NEET-PG:** * **Protective Efficacy:** BCG is **80% effective** against TB Meningitis and Miliary TB in children. * **Strain:** The most common strain used in India is **Danis 1331**. * **Administration:** Given **Intradermally** (0.05 ml for neonates 1 month) using an **Omega syringe**. * **Phenomenon:** BCG is the only vaccine that leaves a permanent scar (at the insertion of the deltoid). * **Direct BCG:** Refers to giving the vaccine without a prior Mantoux test (standard practice in the National Immunization Schedule).

Q: Which of the following statements about tetanus is incorrect?

Herd immunity is present for tetanus.. **Explanation:** **1. Why Option B is the Correct Answer (Incorrect Statement):** Herd immunity occurs when a large portion of a population is immune to an infectious disease, thereby providing indirect protection to those who are not immune by reducing the chain of transmission. **Tetanus is the only vaccine-preventable disease for which herd immunity does not exist.** This is because *Clostridium tetani* is an environmental saprophyte found in soil and animal feces; it is not transmitted from person to person. Vaccination protects only the individual immunized and does not reduce the risk of exposure for others. **2. Analysis of Other Options:** * **Option A:** While the primary series provides initial immunity, antitoxin levels decline over time. For sustained protection, booster doses are recommended every 10 years, but in high-risk scenarios or specific national guidelines, a 5-year interval is often cited for maintaining optimal titers. * **Option C:** Tetanus **cannot be eradicated** because the spores are ubiquitous in the environment (soil). Eradication is only possible for diseases with an exclusive human reservoir (e.g., Smallpox, Polio). * **Option D:** The WHO defines the **Elimination of Neonatal Tetanus** as an incidence of **less than 1 case per 1,000 live births** in every district of a country. India achieved this milestone in 2015. **High-Yield Clinical Pearls for NEET-PG:** * **Type of Immunity:** Tetanus toxoid provides **Active Artificial Immunity**. * **Neonatal Tetanus:** Also known as the "8th-day disease." * **Maternal Immunization:** Two doses of Td (Tetanus-diphtheria) are given during pregnancy to prevent neonatal tetanus via transplacental transfer of IgG antibodies. * **Portal of Entry:** Most common in India is through the umbilical cord stump (Neonatal) or injury/otitis media (Adult).

Q: Which vaccine is recommended for healthcare workers?

Hepatitis B Virus (HBV). **Explanation:** **Hepatitis B Virus (HBV)** is the correct answer because healthcare workers (HCWs) are at a high occupational risk of exposure to blood-borne pathogens via needle-stick injuries or mucosal splashes. HBV is highly infectious; the risk of transmission after a percutaneous injury from an HBeAg-positive source is approximately 30%. The HBV vaccine is a recombinant DNA vaccine that is safe, effective, and universally recommended for all HCWs to prevent chronic infection and its complications (cirrhosis and hepatocellular carcinoma). **Analysis of Incorrect Options:** * **HIV (Option A):** Currently, there is no approved vaccine for HIV due to the virus's high mutation rate and complex evasion of the immune system. Prevention relies on Post-Exposure Prophylaxis (PEP) and universal precautions. * **Hepatitis C (Option C):** There is no vaccine available for HCV. Like HIV, prevention in healthcare settings depends on stringent infection control and prompt management of occupational exposure. * **Cholera (Option D):** This is a water-borne disease. While oral cholera vaccines exist, they are primarily used for travelers to endemic areas or during outbreaks in areas with poor sanitation. It is not a routine occupational requirement for HCWs. **High-Yield Clinical Pearls for NEET-PG:** * **HBV Schedule:** The standard adult schedule is 0, 1, and 6 months (Intramuscular, Deltoid muscle). * **Post-Vaccination Testing:** Anti-HBs titers should be checked 1–2 months after the third dose. A titer **≥10 mIU/mL** indicates adequate protection. * **Non-responders:** If titers are <10 mIU/mL after the first series, a second 3-dose series is recommended. * **Rule of 3s (Transmission risk after needle-stick):** HBV (30%), HCV (3%), HIV (0.3%).

Q: What is the most common cause of vaccine failure?

Maternally derived antibodies. ### Explanation **Correct Answer: D. Maternally derived antibodies** The most common cause of vaccine failure globally is the presence of **maternally derived antibodies (MDAs)**. During pregnancy, IgG antibodies are transferred across the placenta to the fetus, providing passive immunity. However, these circulating antibodies can neutralize the antigens in a vaccine (especially live-attenuated vaccines like Measles) before the infant’s own immune system can mount a primary response. This is why the Measles vaccine is strategically delayed until 9 months of age in endemic areas, as administering it earlier often leads to vaccine failure due to high MDA titers. **Why other options are incorrect:** * **A. Improper storage:** While a major concern for vaccine **potency** (especially regarding the "Cold Chain"), it is a logistical failure rather than the most frequent biological cause of failure in a correctly administered dose. * **B. Improper administration:** While incorrect routes or sites can reduce efficacy, standardized training under the Universal Immunization Programme (UIP) makes this less common than the physiological interference of MDAs. * **C. Improper manufacturing:** Vaccines undergo rigorous quality control and WHO pre-qualification; manufacturing defects are rare and usually lead to batch recalls rather than routine vaccine failure. **High-Yield Clinical Pearls for NEET-PG:** * **Primary Vaccine Failure:** Failure of the vaccine to elicit an initial immune response (e.g., due to MDAs or poor cold chain). * **Secondary Vaccine Failure:** Waning of immunity over time after an initial successful response (requires booster doses). * **Most Heat-Sensitive Vaccine:** Oral Polio Vaccine (OPV). * **Most Heat-Resistant Vaccine:** Hepatitis B / Tetanus Toxoid (TT). * **Measles Vaccine:** The classic example of a vaccine whose timing is dictated by the disappearance of maternal antibodies.

Q: At what temperature should the measles vaccine be stored at a primary health care centre?

+2°C to 8°C. **Explanation:** The correct answer is **C (+2°C to 8°C)**. In the Universal Immunization Programme (UIP) in India, the storage temperature for vaccines at the peripheral level (Primary Health Centres and Community Health Centres) is standardized. While the measles vaccine is heat-sensitive and can be stored at sub-zero temperatures at higher levels of the cold chain (like GMSDs or State stores), it is stored in the **ILR (Ice-Lined Refrigerator)** at **+2°C to 8°C** at the PHC level to ensure operational uniformity and to prevent accidental freezing of other co-stored vaccines. **Analysis of Incorrect Options:** * **A (-20°C):** This is the storage temperature for the **OPV (Oral Polio Vaccine)** at the district level and for measles at the national/regional level. However, at the PHC level, deep freezers are primarily used for preparing ice packs, not for vaccine storage. * **B (0°C):** This is not a standard storage temperature for any vaccine in the cold chain. * **D (Room Temperature):** Measles is a live-attenuated vaccine and is highly heat-sensitive. Exposure to room temperature leads to rapid loss of potency. **High-Yield Clinical Pearls for NEET-PG:** * **Most Heat-Sensitive Vaccine:** OPV (followed by Measles). * **Most Heat-Resistant Vaccine:** TT (Tetanus Toxoid). * **Freeze-Sensitive Vaccines:** Hep B, DPT, Pentavalent, and TT. These must **never** be frozen (the "Shake Test" is used to check if they have been damaged by freezing). * **Reconstitution Rule:** Once reconstituted, the measles vaccine must be used within **4 hours** or discarded. It must be kept on an ice pad during the session. * **VVM (Vaccine Vial Monitor):** Always check the VVM before administration. If the inner square matches or is darker than the outer circle, the vaccine must be discarded.

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.

Question 1

What does the sticker shown on a vaccine vial indicate?

Accepted Answer

Cold chain maintenance

Answer

Efficacy

Answer

Expiry

Answer

Viability

Question 2

Vaccines at a Primary Health Centre (PHC) are stored in which of the following?

Accepted Answer

Ice-lined refrigerator (ILR)

Answer

Ice box

Answer

Deep freezer

Answer

None of the above

Question 3

What is the efficacy of the BCG vaccine for pulmonary tuberculosis?

Accepted Answer

0%

Answer

25%

Answer

33%

Answer

50%

Question 4

All of the following are contraindicated during pregnancy except?

Accepted Answer

Rabies vaccine

Answer

Measles vaccine

Answer

Mumps vaccine

Answer

HPV vaccine

Question 5

Which of the following statements about tetanus is incorrect?

Accepted Answer

Herd immunity is present for tetanus.

Answer

Tetanus protection requires booster doses every 5 years if previously immunized.

Answer

Tetanus cannot be eradicated.

Answer

Elimination of tetanus is defined as less than 1 case per 1,000 live births.

Question 6

Which vaccine is recommended for healthcare workers?

Accepted Answer

Hepatitis B Virus (HBV)

Answer

Human Immunodeficiency Virus (HIV)

Answer

Hepatitis C Virus (HCV)

Answer

Cholera

Question 7

What is the most common cause of vaccine failure?

Accepted Answer

Maternally derived antibodies

Answer

Improper storage

Answer

Improper administration

Answer

Improper manufacturing

Question 8

Under the National Polio Eradication Programme, a case of Acute Flaccid Paralysis 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 stool

Question 9

At what temperature should the measles vaccine be stored at a primary health care centre?

Accepted Answer

+2°C to 8°C

Answer

-20°C

Answer

0°C

Answer

Any temperature not exceeding room temperature

Question 10

Which anti-rabies vaccine has been recommended by WHO?

Accepted Answer

HDCV

Answer

Ducek cell vaccine

Answer

Chick fibroblast vaccine

Answer

Sheep brain vaccine

Immunization and Vaccine-Preventable Diseases — MCQs

Immunization and Vaccine-Preventable Diseases — MCQs

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