Immunization and Vaccine-Preventable Diseases Practice Questions

Q: What is the recommended storage temperature range for vaccines?

+2°C to +8°C. **Explanation:** The correct storage temperature for most vaccines at the primary health center (PHC) and district level is **+2°C to +8°C**. This range is critical for maintaining the "Cold Chain," ensuring that vaccines do not lose their potency due to heat or freezing. **1. Why +2°C to +8°C is correct:** Most vaccines used in the Universal Immunization Programme (UIP), including T-series (DPT, Pentavalent, TT) and Hepatitis B, are **freeze-sensitive**. If stored below 0°C, these vaccines undergo irreversible denaturation. Conversely, live vaccines like Measles and BCG are **heat-sensitive** but stable at this range for short-term storage. The +2°C to +8°C range serves as the "gold standard" safety zone that prevents both freezing and heat-induced degradation. **2. Why other options are incorrect:** * **A & B (-4°C to 4°C):** These ranges involve temperatures at or below freezing. Freezing destroys the potency of adsorbed vaccines (like DPT and Hep B) by damaging the aluminum adjuvant. * **D (+4°C to +12°C):** This range is too warm. Many vaccines, particularly the Oral Polio Vaccine (OPV) and Measles, are highly thermolabile and would degrade rapidly at temperatures above 8°C. **3. High-Yield NEET-PG Clinical Pearls:** * **Most Heat Sensitive Vaccine:** OPV (requires -20°C for long-term storage). * **Most Heat Resistant Vaccine:** TT (Tetanus Toxoid). * **Most Freeze Sensitive Vaccine:** Hepatitis B (followed by DPT/Pentavalent). * **The Shake Test:** Used to check if a vaccine (DPT, TT, Hep B) has been damaged by freezing. If the vaccine settles faster than a control vial after shaking, it has been frozen and must be discarded. * **ILR (Ice-Lined Refrigerator):** The most important component of the cold chain at the PHC level, maintaining +2°C to +8°C even with limited power supply.

Q: All of the following are true regarding the Yellow Fever vaccine EXCEPT?

Route of administration is intramuscular.. The correct answer is **D (Route of administration is intramuscular)** because the Yellow Fever vaccine is traditionally administered via the **Subcutaneous (SC)** route, not intramuscularly. ### **Explanation of Options:** * **Option D (Correct Answer):** The 17D strain vaccine is administered subcutaneously, usually over the deltoid region. Intramuscular injection is avoided to minimize local reactions and because the vaccine was standardized for SC delivery. * **Option A:** The vaccine is indeed a **live attenuated** preparation (using the **17D strain** grown in chick embryos) and is **lyophilized** (freeze-dried), requiring reconstitution with cold sterile physiological saline. * **Option B:** While generally contraindicated, the WHO and National Guidelines state it **can be administered in pregnancy** during an outbreak or if travel to an endemic area is unavoidable, as the risk of the disease outweighs the theoretical risk of the vaccine. * **Option C:** For international travel (under International Health Regulations), the certificate becomes valid **10 days after vaccination** (the time required for protective antibodies to develop). ### **High-Yield Clinical Pearls for NEET-PG:** * **Strain:** 17D (D stands for Dakar, though the 17D lineage is the global standard). * **Validity:** Since 2016, the WHO has declared that a single dose provides **lifelong immunity**; boosters are no longer required for international travel. * **Contraindications:** Infants <6 months, individuals with symptomatic HIV/AIDS, thymic disorders, or **severe egg allergy** (as it is grown in chick embryos). * **Storage:** Must be kept between **0°C to +8°C** and protected from light. Once reconstituted, it must be used within 6 hours (or as per manufacturer instructions, often 30 minutes).

Q: How many fully frozen ice packs should a vaccine carrier contain?

4. **Explanation:** The correct answer is **4**. In the Universal Immunization Programme (UIP), a standard **vaccine carrier** is designed to maintain the cold chain during the transport of vaccines from the primary health center to outreach sessions. It is a small, insulated box with a capacity of approximately 1.6 to 2.4 liters. To ensure the internal temperature remains between +2°C and +8°C, it must be lined with **four conditioned (or fully frozen) ice packs**, placed against the four sides of the carrier. **Analysis of Options:** * **Option A (2):** This is insufficient to maintain the required temperature for the duration of a field session (usually 48–72 hours). Using only two packs would leave gaps, leading to rapid warming. * **Option B (4):** **Correct.** This is the standard requirement for a vaccine carrier. * **Option C (6):** This is the requirement for a **Cold Box (Small)**. Cold boxes are larger than vaccine carriers and require more ice packs (6 to 24 depending on size) to line the bottom and sides. * **Option D (8):** This exceeds the capacity of a standard vaccine carrier and would leave no room for the vaccine vials. **High-Yield NEET-PG Pearls:** * **Conditioning of Ice Packs:** Before placing ice packs in the carrier, they should be "conditioned" (kept at room temperature until water starts sloshing inside) to prevent freezing of DPT, TT, and Hepatitis B vaccines. * **Cold Box vs. Vaccine Carrier:** A Cold Box is used for bulk storage/transport (up to 5–7 days), while a Vaccine Carrier is for local transport (up to 48–72 hours). * **Day Carriers:** These are smaller and require only **2 ice packs**. Do not confuse "Vaccine Carrier" with "Day Carrier."

Q: All are true about the Hepatitis B vaccine except?

It is a polysaccharide-based vaccine.. **Explanation:** The Hepatitis B vaccine is a **recombinant DNA subunit vaccine**, not a polysaccharide vaccine. This is the fundamental reason why Option B is the correct "except" choice. 1. **Why Option B is Correct (The False Statement):** Polysaccharide vaccines (like PPSV23 or Typhoid Vi) are derived from the sugar coating of bacteria. Hepatitis B is a virus, and its vaccine is composed of a **protein** (HBsAg). It is produced using recombinant technology where the HBsAg gene is inserted into *Saccharomyces cerevisiae* (yeast). 2. **Why Option A is Incorrect (True Statement):** This describes the recombinant process. The yeast cell acts as a factory to produce large quantities of the viral surface protein. 3. **Why Option C is Incorrect (True Statement):** The vaccine contains only the surface antigen (HBsAg). Because it lacks the viral DNA (core), it is non-infectious and cannot cause Hepatitis B. 4. **Why Option D is Incorrect (True Statement):** In the National Immunization Schedule (NIS), the intramuscular (IM) injection site for infants is the **anterolateral aspect of the mid-thigh**. In adults, the deltoid is preferred. The gluteal region is avoided as it may lead to lower immunogenicity due to injection into fatty tissue. **High-Yield Clinical Pearls for NEET-PG:** * **Schedule (NIS):** 0, 6, 10, and 14 weeks (Birth dose + 3 doses of Pentavalent). * **Storage:** It is **freeze-sensitive**; store at +2°C to +8°C. Do not freeze (Shake test is used if freezing is suspected). * **Efficacy:** A protective antibody titer is defined as **≥10 mIU/mL** of Anti-HBs. * **Non-responders:** Approximately 5–10% of individuals do not develop immunity; risk factors include smoking, obesity, and old age.

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.

Question 1

What is the recommended storage temperature range for vaccines?

Accepted Answer

+2°C to +8°C

Answer

-4°C to 0°C

Answer

0°C to 4°C

Answer

+4°C to +12°C

Question 2

What is true regarding the elimination of neonatal tetanus?

Accepted Answer

Rate of neonatal tetanus is less than 0.1/1000 live births.

Answer

Rate of neonatal tetanus is more than 1/1000 live births.

Answer

Percentage of deliveries attended by healthcare professionals is less than 50%.

Answer

Percentage of deliveries attended by healthcare professionals is more than 50%.

Question 3

All of the following are true regarding the Yellow Fever vaccine EXCEPT?

Accepted Answer

Route of administration is intramuscular.

Answer

It is a live attenuated, lyophilized vaccine.

Answer

It can be administered in pregnancy.

Answer

WHO recommended validity of vaccination certificate for international travel is from 10 days after vaccination.

Question 4

How many fully frozen ice packs should a vaccine carrier contain?

Accepted Answer

4

Answer

2

Answer

6

Answer

8

Question 5

All are true about the Hepatitis B vaccine except?

Accepted Answer

It is a polysaccharide-based vaccine.

Answer

It is made by inserting the segment of the hepatitis B virus gene into a yeast cell.

Answer

The Hepatitis B Vaccine is identical to the natural hepatitis B surface antigen but does not contain virus DNA.

Answer

The vaccine should be given at the anterolateral side of the left mid-thigh.

Question 6

All of the following are true about Yellow Fever except:

Accepted Answer

Aedes aegypti index should not be more than 10% to ensure freedom from Yellow Fever

Answer

Incubation period is 3-6 days

Answer

Validity of International Certificate of Vaccination lasts up to 10 years

Answer

Urban form is controlled by 17D vaccine

Question 7

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 8

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

Accepted Answer

Whooping cough

Answer

Polio

Answer

Diphtheria

Answer

Tetanus

Question 9

OPV can be used if the vaccine vial monitor (VVM) is showing which of the following conditions?

Accepted Answer

The color of the outer circle is darker than the inner square.

Answer

The color of the outer circle is the same as the inner square.

Answer

The color of the outer circle is lighter than the inner square.

Answer

None of the above.

Question 10

Which of the following is NOT a cholera vaccine?

Accepted Answer

Ty21a

Answer

CVD-103-HgR

Answer

WC-rBS

Answer

mORC-Vax

Immunization and Vaccine-Preventable Diseases — MCQs

Immunization and Vaccine-Preventable Diseases — MCQs

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