Immunization and Vaccine-Preventable Diseases — MCQs

Immunization and Vaccine-Preventable Diseases Indian Medical PG Practice Questions and MCQs

Question 41: How many vaccine vials can a carrier transport daily?

A. 4 vials
B. 8 vials (Correct Answer)
C. 10 vials
D. 16-20 vials

Explanation: **Explanation:** The correct answer is **8 vials (Option B)**. This question pertains to the cold chain equipment used in the Universal Immunization Programme (UIP). **Why 8 vials is correct:** A **Vaccine Carrier** is a small, portable insulated container used to transport vaccines from the Primary Health Centre (PHC) to outreach sessions (sub-centers or village sites). It has a storage capacity of approximately **1.6 to 2.2 liters**. While it can physically hold more, standard guidelines specify it is designed to carry **16–20 vials** total; however, for a single day's immunization session, it is optimized to carry **8 vials** effectively while maintaining the required temperature (2°C to 8°C) using four conditioned ice packs. **Analysis of Incorrect Options:** * **Option A (4 vials):** This is the capacity of a **"Day Carrier."** Day carriers are smaller, use only two ice packs, and are used for very small sessions or for carrying vaccines to nearby houses during pulse polio rounds. * **Option C (10 vials):** This is a distractor and does not correspond to standard UIP equipment specifications. * **Option D (16-20 vials):** This represents the **maximum physical capacity** of a vaccine carrier if packed tightly. However, for daily operational use and to ensure proper air circulation and cooling, the standard functional answer for "daily transport" in exams is 8 vials. **High-Yield Clinical Pearls for NEET-PG:** * **Cold Chain Sequence:** Walk-in-Cooler (State/Regional) → ILR/Deep Freezer (District/PHC) → Vaccine Carrier (Outreach) → Day Carrier (Last mile). * **Ice Packs:** A vaccine carrier requires **4 conditioned ice packs**, whereas a day carrier requires **2**. * **Conditioning:** Ice packs must be "conditioned" (kept at room temperature until water sloshes inside) to prevent freezing sensitive vaccines like DPT, Hep B, and Pentavalent. * **Duration:** A vaccine carrier can maintain the cold chain for **24–48 hours** if unopened.

Question 42: Which of the following vaccines does not provide herd immunity?

A. Hepatitis A
B. Rabies (Correct Answer)
C. Measles
D. Diphtheria

Explanation: **Explanation:** **Herd immunity** (community immunity) occurs when a large portion of a population becomes immune to a disease, making spread from person to person unlikely. This protects individuals who are not immune (e.g., newborns or the immunocompromised). **Why Rabies is the Correct Answer:** Rabies is a **zoonotic disease** transmitted primarily through the bite of an infected animal (e.g., dogs). There is **no human-to-human transmission** of rabies. Since the vaccine prevents the disease in the individual but does not break a chain of human transmission, it does not provide herd immunity. To achieve herd immunity against rabies, the animal population (dogs) must be vaccinated, not the humans. **Analysis of Incorrect Options:** * **Hepatitis A:** Transmitted via the feco-oral route. Vaccination reduces the viral load and shedding in the community, providing indirect protection to the unvaccinated. * **Measles:** Highly contagious via respiratory droplets. The vaccine is highly effective at preventing transmission, and a high coverage (approx. 95%) is essential for herd immunity. * **Diphtheria:** Transmitted via respiratory droplets. While the vaccine is a toxoid (targeting the toxin), it significantly reduces the carriage of *Corynebacterium diphtheriae* in the pharynx, thereby contributing to herd immunity. **NEET-PG High-Yield Pearls:** * **Vaccines NOT providing Herd Immunity:** Rabies, Tetanus (non-communicable), and Injectable Polio Vaccine (IPV) (provides individual protection but does not prevent intestinal shedding/transmission as effectively as OPV). * **Herd Immunity Threshold:** This depends on the **Basic Reproduction Number ($R_0$)**. The formula is $H = 1 - (1/R_0)$. * **Measles** has the highest $R_0$ (12–18), requiring the highest herd immunity threshold (92–95%).

Question 43: What is the recommended minimum age for vaccination with the human papillomavirus (HPV) vaccine?

A. 11 years
B. 9 years (Correct Answer)
C. 15 years
D. 13 years

Explanation: **Explanation:** The Human Papillomavirus (HPV) vaccine is most effective when administered before the onset of sexual activity (pre-exposure). According to both the **World Health Organization (WHO)** and the **National Technical Advisory Group on Immunization (NTAGI)** in India, the recommended minimum age for vaccination is **9 years**. **Why 9 years is correct:** Clinical studies demonstrate that the immune response to the HPV vaccine is significantly more robust in younger adolescents (9–14 years) compared to older teens. Starting at age 9 allows for a two-dose schedule, which provides equivalent protection to a three-dose schedule in older individuals. **Analysis of Incorrect Options:** * **11 years (Option A):** While 11–12 years is the *routine* age for vaccination in many Western countries (like the US), it is not the *minimum* age. The vaccine is licensed and recommended starting from age 9. * **13 years & 15 years (Options C & D):** These are considered "catch-up" ages. While vaccination is still highly recommended at these ages, they are well beyond the earliest recommended window for initiating the series. **High-Yield NEET-PG Pearls:** * **Dosage Schedule:** * **9–14 years:** 2 doses (0 and 6 months). * **15–45 years:** 3 doses (0, 1–2, and 6 months). * **Cervavac:** India’s first indigenous quadrivalent HPV vaccine (qHPV) targeting types 6, 11, 16, and 18. * **Target Strains:** Types **16 and 18** are responsible for ~70% of cervical cancers; Types **6 and 11** cause genital warts. * **Primary Prevention:** HPV vaccination is a form of primary prevention against cervical, anal, and oropharyngeal cancers.

Question 44: What is the recommended vaccination strategy for rubella?

A. Women of reproductive age (15-49 years) (Correct Answer)
B. Infants
C. Adolescent girls
D. Children aged 1-14 years

Explanation: ### Explanation The primary objective of Rubella vaccination is not just to prevent the mild, self-limiting infection in children, but to prevent **Congenital Rubella Syndrome (CRS)**. When a non-immune pregnant woman contracts Rubella, the virus can cross the placenta, leading to severe fetal malformations, deafness, and cardiac defects. **Why Option A is Correct:** Targeting **women of reproductive age (15-49 years)** is the most effective strategy to provide immediate protection against CRS. By ensuring this cohort is immune, the risk of vertical transmission during pregnancy is eliminated. In the context of public health and NEET-PG, this is often referred to as the "selective" or "targeted" strategy to reduce the disease burden where it is most devastating. **Why Other Options are Incorrect:** * **B & D (Infants/Children):** While the Universal Immunization Programme (UIP) in India now uses the MR (Measles-Rubella) vaccine for children (9 months to 15 years) to build herd immunity, this is a long-term strategy. The immediate priority for preventing CRS remains the reproductive age group. * **C (Adolescent girls):** While important, this is a subset of the reproductive age group. Targeting the entire 15-49 age bracket ensures a wider safety net for all potential pregnancies. **High-Yield Clinical Pearls for NEET-PG:** * **Vaccine Type:** Live attenuated (RA 27/3 strain is most common). * **Contraindication:** Pregnancy. Women should be advised to **avoid pregnancy for 4 weeks (1 month)** after receiving the Rubella vaccine. * **CRS Triad (Gregg’s Triad):** Cataract, Sensorineural deafness, and Cardiac defects (Patent Ductus Arteriosus). * **Diagnostic Tip:** Rubella is also known as "German Measles" or "3-day measles."

Question 45: The influenza vaccine contains all strains of influenza virus except which one?

A. H1N1
B. H3N2
C. H2N1 (Correct Answer)
D. Influenza B

Explanation: **Explanation:** The influenza vaccine is designed to protect against the strains currently circulating in the human population that pose the greatest public health threat. **Why H2N1 is the Correct Answer:** The **H2N1** subtype is not a common human pathogen and is not included in the seasonal influenza vaccine. While H2N2 caused the "Asian Flu" pandemic in 1957, it has not circulated in humans since 1968. H2N1, specifically, is not a standard component of any WHO-recommended trivalent or quadrivalent vaccine formulation. **Analysis of Incorrect Options:** * **H1N1 (Option A):** This is a subtype of Influenza A. Since the 2009 pandemic, the H1N1 strain (specifically A/pdm09) has been a core component of the seasonal vaccine. * **H3N2 (Option B):** This is another subtype of Influenza A that causes significant morbidity and mortality, especially in the elderly. It is a standard component of both trivalent and quadrivalent vaccines. * **Influenza B (Option D):** Influenza B viruses are included in all seasonal vaccines. Trivalent vaccines contain one lineage (Victoria or Yamagata), while quadrivalent vaccines contain both. **High-Yield NEET-PG Pearls:** 1. **Composition:** The **Quadrivalent vaccine** (most common today) contains two Influenza A strains (H1N1, H3N2) and two Influenza B lineages (Victoria, Yamagata). 2. **Antigenic Shift vs. Drift:** *Drift* (point mutations) causes seasonal epidemics; *Shift* (genetic reassortment) causes pandemics. 3. **Timing:** Because the virus undergoes frequent antigenic drift, the WHO reviews and updates the vaccine composition twice a year (Northern and Southern Hemisphere recommendations). 4. **Contraindication:** Severe egg allergy is a traditional precaution (though cell-based vaccines now exist).

Question 46: All of the following is true about Hepatitis B Vaccination except?

A. Surgeons and healthcare workers must be vaccinated.
B. It is recommended to be given immediately at birth.
C. It is a live attenuated vaccine. (Correct Answer)
D. Booster dose is indicated if there are poor titres.

Explanation: **Explanation:** **1. Why Option C is the Correct Answer (The False Statement):** Hepatitis B vaccine is **not** a live attenuated vaccine. It is a **Recombinant DNA vaccine** (Subunit vaccine). It is produced by inserting the gene for Hepatitis B surface antigen (HBsAg) into common baker’s yeast (*Saccharomyces cerevisiae*). The yeast then produces pure HBsAg, which is harvested and used as the immunogen. **2. Analysis of Other Options:** * **Option A:** Healthcare workers (HCWs), especially surgeons and laboratory staff, are at high risk for occupational exposure to blood-borne pathogens. Vaccination is mandatory to prevent horizontal transmission. * **Option B:** Under the National Immunization Schedule (NIS), a **birth dose** is recommended within 24 hours to prevent mother-to-child (vertical) transmission, which carries a high risk of chronic carrier status. * **Option C:** While routine boosters are not recommended for the general population, a booster dose is indicated for individuals (especially HCWs) who fail to achieve protective antibody levels (**Anti-HBs titres < 10 mIU/mL**) after the primary series. **3. High-Yield Clinical Pearls for NEET-PG:** * **Type:** First-generation vaccines were plasma-derived; current (second-generation) vaccines are recombinant. * **Route & Site:** Intramuscular (IM). In infants, it is given in the **Anterolateral aspect of the thigh**; in adults, the **Deltoid**. *Note: Never give it in the gluteal region as it results in lower immunogenicity due to fat deposition.* * **Schedule:** 0, 1, and 6 months (standard) or as part of the Pentavalent vaccine (6, 10, 14 weeks). * **Efficacy:** Highly effective; 95% of vaccinees develop protective immunity. Non-responders are more common among smokers, the obese, and the elderly.

Question 47: How much time does it take for the finding shown below, after BCG vaccination?

A. 1-2 days
B. 1-2 weeks
C. 2-4 weeks
D. 6-12 weeks (Correct Answer)

Explanation: ***6-12 weeks*** - The **BCG scar formation** occurs at 6-12 weeks post-vaccination, representing the final stage of the immune response and successful immunization. - This timeframe allows for complete **granulomatous inflammation** and subsequent healing, resulting in a characteristic **permanent scar**. *1-2 days* - This represents the immediate **injection site reaction** with minimal inflammation and **erythema**. - Too early for any significant **cell-mediated immune response** or meaningful BCG-related changes. *1-2 weeks* - Shows early **inflammatory response** with **induration** and **erythema** but no ulceration or significant tissue reaction. - Represents the **initial cellular infiltration** phase, not the complete immunological process. *2-4 weeks* - Characterized by **papule formation** and possible **ulceration** as the immune response intensifies. - Still represents an **intermediate stage** before complete healing and scar formation occurs.

Question 48: What immunization is typically given at 9 months of age?

A. Measles (Correct Answer)
B. DPT
C. BCG
D. All of the above

Explanation: **Explanation:** Under the National Immunization Schedule (NIS) in India, the **9th month** marks a critical transition from primary infancy vaccinations to the introduction of live-attenuated viral vaccines. **1. Why Measles is Correct:** The first dose of the **Measles-Rubella (MR)** vaccine is administered at 9 completed months (up to 12 months). It is not given earlier because maternal antibodies (IgG) persist in the infant’s circulation for several months, which can neutralize the vaccine virus and prevent an adequate immune response. By 9 months, these maternal antibodies have waned sufficiently to allow for successful seroconversion. **2. Why Other Options are Incorrect:** * **BCG (Bacillus Calmette–Guérin):** This is administered **at birth** (or as soon as possible up to 1 year). It is a live bacterial vaccine used to prevent severe forms of childhood tuberculosis. * **DPT (Diphtheria, Pertussis, Tetanus):** The primary series of DPT (given as part of the Pentavalent vaccine) is administered at **6, 10, and 14 weeks**. A DPT booster is later given at 16–24 months, not at 9 months. **3. NEET-PG High-Yield Pearls:** * **Vitamin A:** The 1st dose of Vitamin A (1 lakh IU) is administered concurrently with the MR vaccine at 9 months. * **JE Vaccine:** In endemic districts, the 1st dose of the Japanese Encephalitis (JE) vaccine is also given at 9 months. * **PCV Booster:** The booster dose of the Pneumococcal Conjugate Vaccine (PCV) is scheduled at 9 months. * **Route:** MR vaccine is administered **Subcutaneously** in the right upper arm.

Question 49: What is true about the DPT vaccine?

A. Has an efficacy greater than 95%
B. Prevents the development of a carrier state (Correct Answer)
C. Prevents the development of Diphtheria
D. Should be stored at -4 degrees Celsius

Explanation: ### Explanation **Correct Answer: B. Prevents the development of a carrier state** The Diphtheria component of the DPT vaccine is a **toxoid**. While toxoids primarily induce antitoxic immunity (protecting against the systemic effects of the toxin), the DPT vaccine is unique in its epidemiological impact. By inducing high levels of circulating antibodies, it significantly reduces the colonization of *Corynebacterium diphtheriae* in the nasopharynx. This effectively **prevents the development of a carrier state** in immunized individuals, thereby breaking the chain of transmission in the community. **Analysis of Incorrect Options:** * **Option A:** The efficacy of the Pertussis component is generally lower, ranging from **70% to 80%**. It is not >95%. * **Option C:** This is a common distractor. The vaccine prevents the **clinical disease** (the manifestations caused by the toxin) rather than the infection itself. However, in the context of NEET-PG, the prevention of the "carrier state" is the more specific and classically tested epidemiological attribute of DPT. * **Option D:** DPT is a **freeze-sensitive vaccine**. It must be stored in the **ILR (Ice-Lined Refrigerator) at +2°C to +8°C**. Storing it at -4°C would cause the vaccine to freeze, leading to the denaturation of the adjuvant (aluminum salts) and loss of potency. **High-Yield Clinical Pearls for NEET-PG:** * **The Shake Test:** Used to check if a DPT/Pentavalent vaccine has been damaged by freezing. If the vaccine is "frozen and thawed," it will show rapid sedimentation. * **Site of Injection:** Intramuscular (IM) in the **anterolateral aspect of the mid-thigh** (never the gluteal region in infants due to risk of sciatic nerve injury). * **Contraindication:** A history of encephalopathy within 7 days of a previous dose is an absolute contraindication for the Pertussis component (switch to DT). * **Composition:** Diphtheria Toxoid, Tetanus Toxoid, and Killed *B. pertussis* bacilli.

Question 50: All of the following are contraindications to pertussis-containing vaccines EXCEPT?

A. Uncontrolled epilepsy
B. Anaphylactic reaction to a previous dose
C. Egg allergy (Correct Answer)
D. Progressive encephalopathy

Explanation: **Explanation:** The correct answer is **Egg allergy**. Pertussis-containing vaccines (like DPT or DTaP) are not grown in eggs; they are bacterial vaccines. Therefore, an egg allergy is **not** a contraindication. In contrast, vaccines like Influenza, Yellow Fever, and MMR (though MMR is generally safe) are related to egg proteins. **Analysis of Options:** * **Uncontrolled Epilepsy:** Pertussis vaccine is associated with a risk of febrile seizures. In children with evolving or unstable neurological disorders (like uncontrolled epilepsy), the vaccine is deferred until the condition is stabilized to avoid diagnostic confusion regarding the cause of seizures. * **Anaphylactic Reaction:** This is a universal contraindication for any vaccine. If a patient develops a life-threatening allergic reaction to a previous dose or any component of the vaccine, further doses are strictly prohibited. * **Progressive Encephalopathy:** This is an absolute contraindication. If a child has an undiagnosed, evolving neurological condition or develops encephalopathy within 7 days of a previous dose (not attributable to another cause), subsequent pertussis doses must be withheld. **High-Yield Clinical Pearls for NEET-PG:** * **Absolute Contraindications for Pertussis:** 1. Anaphylaxis to vaccine components. 2. Encephalopathy within 7 days of a previous dose. * **Precautions (Deferral):** Fever >40.5°C, collapse/shock-like state (HIE), or persistent crying (>3 hours) within 48 hours of a previous dose. * **Safe to Administer:** Stable neurological conditions (e.g., well-controlled seizures, cerebral palsy), family history of seizures, and minor acute illnesses. * **Switching:** If pertussis is contraindicated, the immunization series should be completed with **DT (Diphtheria and Tetanus)** instead of DPT.

Practice by Chapter

Principles of Immunization

Practice Questions

Types of Vaccines

Practice Questions

Universal Immunization Program

Practice Questions

Cold Chain System

Practice Questions

Vaccine Storage and Handling

Practice Questions

Adverse Events Following Immunization

Practice Questions

National Immunization Schedule

Practice Questions

Polio Eradication

Practice Questions

Measles Elimination

Practice Questions

Tetanus Control

Practice Questions

New and Underutilized Vaccines

Practice Questions

Vaccination Coverage Assessment

Practice Questions

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