Immunization and Vaccine-Preventable Diseases — MCQs

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

Question 381: Management of non-immunized diphtheria contacts includes all except:

A. Daily throat examination
B. Prophylactic penicillin
C. Daily throat swab culture (Correct Answer)
D. Weekly throat swab examination

Explanation: ***Daily throat swab culture*** - **Daily throat swab cultures** are not part of standard management for non-immunized diphtheria contacts as they are impractical, resource-intensive, and unnecessary. - Standard practice involves a **single throat/nasal culture** at the time of contact identification to detect carriers, not repeated daily cultures. - Daily clinical surveillance (visual examination) is sufficient for monitoring symptom development. *Daily throat examination* - **Daily clinical throat examination** is a crucial component of contact management for early detection of membrane formation or pharyngitis. - This allows prompt isolation and treatment if symptoms develop during the incubation period (2-5 days). - Visual inspection is practical and cost-effective for daily monitoring. *Prophylactic penicillin* - **Prophylactic antibiotics** (benzathine penicillin single dose IM or 7-10 days of oral erythromycin) are essential for all diphtheria contacts regardless of immunization status. - This eradicates potential colonization with *Corynebacterium diphtheriae* and prevents disease development. - Reduces transmission risk during the incubation period. *Weekly throat swab examination* - While **not part of routine management**, weekly swabs are more reasonable than daily cultures if extended monitoring is needed in special circumstances. - Standard protocol involves a **single culture** at identification, not repeated weekly sampling. - The key distinction: daily cultures are clearly excessive, making this the correct answer for what is NOT included in standard management.

Question 382: Mass vaccination is ineffective in inducing 'herd immunity' for:

A. Poliomyelitis
B. Tetanus (Correct Answer)
C. None of the options
D. Measles

Explanation: ***Tetanus (Correct Answer)*** - **Herd immunity** relies on reducing person-to-person transmission, which is not applicable to tetanus as it is acquired through **environmental exposure** (soil contaminated with *Clostridium tetani* spores), not human contact - Vaccination against tetanus provides **individual protection only** and does not prevent disease spread within a population, making mass vaccination ineffective for herd immunity - Tetanus is a **non-communicable disease** - immunity in others does not protect unvaccinated individuals *Poliomyelitis (Incorrect)* - Mass vaccination for poliomyelitis has been highly effective in establishing **herd immunity**, leading to near-global eradication - The vaccine prevents viral shedding and breaks the chain of transmission - High vaccination coverage protects unvaccinated individuals through reduced viral circulation *Measles (Incorrect)* - Mass vaccination against measles is extremely effective in inducing **herd immunity** due to its high transmissibility (R₀ = 12-18) - Requires **~95% vaccination coverage** to maintain herd immunity - Classic example where high vaccination rates protect vulnerable individuals who cannot be vaccinated *None of the options (Incorrect)* - This is incorrect because tetanus is a clear example where mass vaccination does **not** induce herd immunity - The disease's environmental transmission pattern makes herd immunity irrelevant for disease control

Question 383: The typical upper range of typhoid vaccine efficacy is -

A. 100%
B. 95%
C. 85% (Correct Answer)
D. 50%

Explanation: ***Correct: 85%*** - The **polysaccharide typhoid vaccine (Vi)** and the **oral live attenuated vaccine (Ty21a)** typically offer protection rates ranging from 50% to **85%**. - While varying depending on the study population and vaccine type, **85%** represents the higher end of the reported efficacy for current typhoid vaccines. - This is the typical **upper range** of protection achieved in clinical trials and field studies. *Incorrect: 100%* - **No vaccine** offers 100% efficacy, as individual immune responses and circulating pathogen strains can influence protection. - While highly effective, typhoid vaccines provide significant reduction in disease risk but not absolute immunity. *Incorrect: 95%* - While a very good efficacy rate, 95% is generally **higher than the typical upper range** observed in clinical trials for currently available typhoid vaccines. - This level of efficacy is more commonly associated with vaccines against diseases like measles or mumps. *Incorrect: 50%* - While **50% efficacy** falls within the lower range of protection for some typhoid vaccines (especially the oral live attenuated vaccine over a longer period), it is **not the typical upper range**. - The question asks for the typical *upper* range, indicating a higher level of protection achieved by these vaccines.

Question 384: The schedule of HDCV in rabies is:

A. 3, 7, 14, 16, 18
B. 0, 3, 7, 14, 28 (Correct Answer)
C. 0, 3, 14, 28, 90
D. 0, 7, 14, 16, 18

Explanation: ***0, 3, 7, 14, 28*** - This schedule represents the **standard post-exposure prophylaxis (PEP)** for rabies using **Human Diploid Cell Vaccine (HDCV)**, administered on days 0, 3, 7, 14, and 28. - This regimen ensures adequate **antibody production** to neutralize the rabies virus after potential exposure. *3, 7, 14, 16, 18* - This schedule is **not a recognized or standard** vaccination protocol for rabies with HDCV. - Deviations from the recommended schedule can compromise the **efficacy of post-exposure prophylaxis**. *0, 3, 14, 28, 90* - While days 0, 3, 14, and 28 are part of some rabies vaccination protocols, the addition of a dose on **day 90** is not typically part of the standard HDCV PEP schedule. - An extended schedule like this might be considered in specific, rare circumstances or for **pre-exposure prophylaxis**, but it's not the primary PEP. *0, 7, 14, 16, 18* - This schedule is **not a standard or approved** regimen for rabies post-exposure prophylaxis using HDCV. - The inclusion of days 16 and 18 is arbitrary and does not align with the established scientific basis for **optimal immune response**.

Question 385: Which is not given at the time of birth?

A. Hepatitis B
B. HiB (Correct Answer)
C. OPV
D. BCG

Explanation: ***HiB*** - The **Haemophilus influenzae type b (Hib)** vaccine is given as part of the **pentavalent vaccine** starting at **6 weeks of age**, with subsequent doses at 10 and 14 weeks in the Indian National Immunization Schedule. - It is not administered at birth because maternal antibodies present in newborns can interfere with the vaccine's effectiveness, and optimal immune response is achieved when vaccination begins at 6 weeks. *Hepatitis B* - The **Hepatitis B vaccine** is routinely given at birth (Hepatitis B-0), preferably within the first 12-24 hours, to protect against perinatal transmission. - Early vaccination is crucial for preventing chronic infection in infants born to mothers with Hepatitis B infection. *OPV* - The **oral polio vaccine (OPV-0)** is given at birth as a "zero dose" to provide early protection against polio. - This initial birth dose helps establish gut immunity before the standard primary series at 6, 10, and 14 weeks. *BCG* - The **Bacille Calmette-Guérin (BCG) vaccine** for tuberculosis is given at birth in India due to the high prevalence of tuberculosis. - Its purpose is to protect infants and young children from severe forms of the disease, such as tuberculous meningitis and disseminated TB.

Question 386: Hepatitis A vaccine schedule - True is ?

A. Single dose of live attenuated vaccine
B. Recommended at the age of 12 months
C. None are true
D. 2 doses of inactivated vaccine 6-18 months apart (Correct Answer)

Explanation: ***2 doses of inactivated vaccine 6-18 months apart*** - The Hepatitis A vaccine is an **inactivated (killed)** vaccine, and the standard schedule involves **two doses** given **6 to 18 months apart** for lasting protection. - This regimen ensures a robust and sustained **antibody response**, providing long-term immunity against Hepatitis A virus infection. - This option correctly describes both the **vaccine type** and the **complete dosing schedule**. *Single dose of live attenuated vaccine* - The Hepatitis A vaccine is an **inactivated vaccine**, not a live attenuated one. - A single dose does not provide the same level of long-term protection as the recommended two-dose schedule. *Recommended at the age of 12 months* - While this statement is factually true (Hepatitis A vaccine is recommended for children starting at **12-23 months of age** as per IAP guidelines), it only addresses the **timing of initiation**, not the complete vaccine schedule. - The question asks about the vaccine schedule, which encompasses the **type of vaccine** and **number of doses with intervals**, making the first option more comprehensive and specific. *None are true* - The first option accurately describes the type and complete schedule of the Hepatitis A vaccine. - Therefore, it is incorrect to state that none of the given options are true.

Question 387: A full course of immunization against tetanus with 3 doses of tetanus toxoid confers immunity for how many years?

A. 5
B. 10 (Correct Answer)
C. 15
D. 20

Explanation: ***10*** - A complete primary series of tetanus toxoid immunizations (3 doses) provides protection against **tetanus** for approximately **10 years**. - Subsequent booster doses are recommended every 10 years to maintain adequate immunity. *5* - While some vaccines offer shorter protection, a full course of **tetanus toxoid** provides immunity for a longer duration than 5 years. - A 5-year interval is often considered for individuals with a **tetanus-prone wound** if their last dose was more than 5 years ago, but not for routine primary immunization. *15* - The standard recommendation for **booster doses** and the duration of protection after a primary series of tetanus toxoid is typically 10 years, not 15 years. - Extending the interval between doses beyond 10 years for routine boosters could reduce overall protection. *20* - A 20-year duration of immunity is significantly longer than the established protection period for a full course of **tetanus toxoid immunization**. - No current guidelines support a 20-year interval for routine tetanus vaccination.

Question 388: CYD-TDV vaccine is used for which of the following infections?

A. Dengue (Correct Answer)
B. Japanese encephalitis
C. Yellow fever
D. Malaria

Explanation: ***Dengue*** - CYD-TDV, also known as **Dengvaxia**, is the first vaccine approved for the prevention of **dengue disease** caused by all four serotypes in individuals aged 9 to 45 years. - Its use is specifically recommended for individuals with confirmed prior **dengue infection** due to concerns about increased risk of severe dengue in seronegative individuals receiving the vaccine. *Japanese encephalitis* - Vaccines for Japanese encephalitis are distinct and include inactivated (e.g., **IXIARO**, **JE-VAX**) and live-attenuated (e.g., **SA14-14-2**) formulations. - These vaccines target the **Japanese encephalitis virus** and are used in regions where the disease is endemic. *Yellow fever* - The vaccine for yellow fever is a **live-attenuated vaccine** (e.g., **YF-Vax**, **Stamaril**) and is commonly administered to travelers to endemic areas and residents of those regions. - It provides effective protection against the **yellow fever virus** and is not related to CYD-TDV. *Malaria* - The RTS,S/AS01 (or **Mosquirix**) vaccine is the first and only malaria vaccine to have received a positive scientific opinion from a regulatory authority for use outside of sub-Saharan Africa. - Malaria is caused by **Plasmodium parasites**, not a virus, and its vaccine development is ongoing and distinct from viral vaccines like CYD-TDV.

Question 389: An event that is caused by an error in vaccine preparation, handling, or administration is called as:

A. Programme error (Correct Answer)
B. Injection reaction
C. Coincidental event
D. Vaccine reaction

Explanation: ***Programme error*** - A **programme error** refers to an unintended event that occurs due to mistakes in **vaccine handling, storage, preparation, or administration**, rather than an inherent property of the vaccine itself. - This type of error can lead to **adverse events** ranging from local reactions (e.g., abscesses) to systemic effects if the vaccine is improperly prepared or administered (e.g., incorrect site, dose, or expired product). *Injection reaction* - An **injection reaction** is a common, mild, and usually transient side effect directly caused by the **injection process** itself, regardless of the vaccine substance. - Examples include **pain, redness, or swelling** at the injection site, or fainting due to anxiety (vasovagal syncope), which are expected reactions and not due to a preparation error. *Coincidental event* - A **coincidental event** is an adverse health event that happens to occur **around the time of vaccination** but is not causally related to the vaccine or the vaccination process. - These events would have occurred regardless of vaccination and are often related to **pre-existing conditions** or other independent factors. *Vaccine reaction* - A **vaccine reaction** (or vaccine adverse event) is an adverse effect inherently caused by the **vaccine's biological properties** when administered correctly. - This refers to the body's expected immune or physiological response to the vaccine components, such as **fever, malaise, or mild localized swelling**, not errors in administration.

Question 390: Which vaccine has the maximum efficacy among the following?

A. TT
B. OPV
C. Measles (Correct Answer)
D. BCG

Explanation: ***Measles*** - The measles vaccine (usually MMR or monovalent measles) has an **extremely high efficacy rate**, often exceeding 97% after two doses in preventing measles infection. - This high efficacy contributes significantly to the success of measles elimination programs globally. *TT (Tetanus Toxoid)* - The tetanus toxoid vaccine is highly effective in preventing tetanus, usually around **80-99% efficacy**, after a full primary series and boosters. - However, its efficacy is generally considered slightly lower or comparable to measles, especially when considering sustained, lifelong protection which requires boosters. *OPV (Oral Polio Vaccine)* - OPV offers good protection against polio, with **efficacy rates typically around 90-95%** after multiple doses. - While effective, its efficacy can be influenced by factors like concurrent intestinal infections, slightly reducing its effectiveness in some populations compared to the consistency of the measles vaccine. *BCG (Bacillus Calmette-Guérin)* - BCG vaccine's efficacy against **pulmonary tuberculosis** in adults is highly variable and ranges from 0% to 80%, depending on the geographical location and population studied. - It is more consistently effective in preventing severe forms of tuberculosis, such as **meningeal TB** and **miliary TB**, in children, but its overall efficacy against all forms of TB is generally lower than other common vaccines.

Practice by Chapter

Principles of Immunization

Practice Questions

Types of Vaccines

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Universal Immunization Program

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Cold Chain System

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Vaccine Storage and Handling

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Adverse Events Following Immunization

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National Immunization Schedule

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Polio Eradication

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Measles Elimination

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Tetanus Control

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New and Underutilized Vaccines

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Vaccination Coverage Assessment

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