Immunization and Vaccine-Preventable Diseases — MCQs

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

Question 441: Under the eradication of congenital rubella syndrome program, the first priority group for rubella vaccination is

A. All female children at one year
B. All non pregnant women
C. All adolescent non pregnant girls 15 to 24 years of age
D. All non pregnant women of age 15 to 34 (Correct Answer)

Explanation: ***All non pregnant women of age 15 to 34*** - This age group represents the most significant **childbearing potential**, making vaccination crucial to prevent **congenital rubella syndrome (CRS)** in future pregnancies. - Vaccinating women in this age range directly addresses the primary goal of the eradication program by reducing the risk of rubella infection during pregnancy. *All female children at one year* - While important for childhood immunity, vaccinating at one year is not the highest priority for the **eradication of CRS**, as these children are not yet at risk of childbearing. - The immediate focus for CRS eradication is on women who are or will soon be of **childbearing age**. *All non pregnant women* - This option is too broad and includes women beyond **childbearing age** (e.g., post-menopausal), for whom the risk of CRS is no longer relevant. - When prioritizing resources, it's more effective to target the specific age group at risk of transmitting rubella to their fetuses. *All adolescent non pregnant girls 15 to 24 years of age* - This group is certainly important, but it omits women from **25 to 34 years of age** who also have significant childbearing potential. - To maximize the impact on CRS eradication, the recommended age range is typically broader, encompassing the full period of high fertility.

Question 442: Which of the following statements about the diphtheria vaccine is true?

A. For infant DPT is the vaccine of choice
B. Can be given as pentavalent vaccine (Correct Answer)
C. First dose is given at 4 weeks of age
D. None of the options

Explanation: ***Can be given as pentavalent vaccine*** - The diphtheria vaccine is commonly administered as part of a **pentavalent vaccine**, which also includes tetanus, pertussis, Haemophilus influenzae type b (Hib), and hepatitis B. - This combination vaccine simplifies the immunization schedule and provides protection against multiple diseases with fewer injections. *For infant DPT is the vaccine of choice* - While DPT (diphtheria, pertussis, tetanus) was historically used, many countries have transitioned to the **pentavalent vaccine** for infants. - The pentavalent vaccine offers broader protection by adding Hib and hepatitis B, making it the preferred choice in many regions. *First dose is given at 4 weeks of age* - The first dose of the **diphtheria vaccine** (often as part of the pentavalent vaccine) is typically given at **6 weeks of age**, not 4 weeks. - This timing aligns with established immunization schedules globally, such as those recommended by the WHO. *None of the options* - This statement is incorrect because the option regarding the diphtheria vaccine being given as a pentavalent vaccine is true. - The use of combination vaccines like the pentavalent vaccine is a standard and effective immunization strategy.

Question 443: Minimum accepted interval between two doses of DPT vaccine in the primary series?

A. 2 weeks
B. 4 weeks (Correct Answer)
C. 6 weeks
D. 8 weeks

Explanation: ***4 weeks*** - A minimum interval of **4 weeks (28 days)** is required between doses of most inactivated vaccines, including DPT, to allow for an adequate immune response to the previous dose. - This interval ensures optimal **immunogenicity** and sufficient time for antibody production, while also preventing immune interference. *2 weeks* - An interval of **2 weeks** is generally considered too short for most inactivated vaccines like DPT. - This short interval may lead to a suboptimal immune response or **immune interference**, rendering subsequent doses less effective. *6 weeks* - While an interval of **6 weeks** would be acceptable for DPT, it is not the *minimum* accepted interval. - Extending the interval beyond the minimum does not typically harm the immune response but might delay the completion of the primary vaccination series. *8 weeks* - An interval of **8 weeks** is also acceptable for DPT but is not the *minimum* required. - This longer interval may be used in specific schedules but does not represent the earliest possible time for the next dose.

Question 444: Reconstituted measles vaccine should be used within -

A. 1 hour
B. 6 hours (Correct Answer)
C. 3 hours
D. 12 hours

Explanation: ***6 hours*** - Reconstituted measles vaccine should be used within **6 hours** of reconstitution, provided it has been kept between **+2°C and +8°C** and protected from sunlight. - This time limit helps ensure the vaccine's **potency and efficacy** as the live attenuated virus degrades rapidly once diluted. *1 hour* - A 1-hour window is generally too short for efficient use, especially in mass vaccination settings, and is not the recommended standard for measles vaccine. - While some vaccines might have a shorter use-by time, the measles vaccine's stability allows for a longer period. *3 hours* - Although it falls within the 6-hour limit, 3 hours is not the maximum recommended time for reconstituted measles vaccine use. - Adhering to the full 6-hour window allows for better logistical planning and resource utilization during vaccination campaigns. *12 hours* - Using reconstituted measles vaccine beyond 6 hours increases the risk of **loss of potency** due to degradation of the live attenuated virus. - This could lead to vaccine failure and inadequate immune response in the vaccinated individual.

Question 445: Which is the only infectious disease that has been eradicated worldwide?

A. Polio
B. Diphtheria
C. Measles
D. Smallpox (Correct Answer)

Explanation: ***Smallpox*** - **Smallpox** was declared eradicated by the World Health Organization in **1980**, following a successful global vaccination campaign. - This was possible due to its **human-only reservoir**, characteristic clinical features, and an effective vaccine. *Polio* - While significant progress has been made towards **polio eradication**, it is not yet fully eradicated, with cases still reported in a few endemic countries. - The disease is caused by the **poliovirus** and is preventable by vaccination, but challenges like vaccine hesitancy and conflict impede full eradication. *Diphtheria* - **Diphtheria** is a serious bacterial infection that is preventable by vaccination and has seen a drastic reduction in cases, but it has not been eradicated worldwide. - Outbreaks still occur in regions with low vaccination coverage, demonstrating its continued presence. *Measles* - **Measles** is a highly contagious viral disease that is preventable by a safe and effective vaccine, but it is far from eradicated. - Outbreaks regularly occur in many parts of the world, especially in areas with suboptimal vaccination rates.

Question 446: What is the minimum interval between the administration of two live vaccines, such as MMR and Varicella?

A. 4 weeks (Correct Answer)
B. 6 weeks
C. 2 weeks
D. 8 weeks

Explanation: ***4 weeks*** - Administering live vaccines simultaneously is generally recommended; however, if not given on the same day, a minimum interval of **4 weeks (28 days)** is necessary. - This interval allows the immune system to fully respond to the first vaccine, preventing potential interference with the replication and efficacy of the second live vaccine. - **Standard recommendation** by CDC, WHO, and IAP for spacing non-simultaneous live vaccines. *2 weeks* - A 2-week interval is generally **too short** for optimal immune response and to prevent potential interference between two live vaccines. - Insufficient time might lead to **reduced seroconversion rates** for the second vaccine, as the immune system is still processing the first. *6 weeks* - While a 6-week interval is safe and effective, it is **not the minimum required interval** between two live vaccines if not given on the same day. - Waiting longer than necessary may **delay protection** against preventable diseases without providing additional immunological benefit compared to the 4-week interval. *8 weeks* - An 8-week interval is also safe but **exceeds the minimum recommended timeframe** for live vaccine administration if not co-administered. - Prolonging the interval beyond 4 weeks **does not enhance efficacy** and may leave the individual susceptible to disease for a longer period.

Question 447: Which of the following is NOT a criterion for measles elimination?

A. Absence of continuous measles virus transmission
B. Incidence rate < 1 per million population
C. High vaccination coverage (>95%)
D. Transmission at low level (Correct Answer)

Explanation: ***Transmission at low level*** - Measles **elimination** strictly requires the **absence of endemic measles virus transmission**, not merely a low level of transmission. - Low-level transmission indicates ongoing circulation of the virus, which is incompatible with the definition of elimination. *Absence of continuous measles virus transmission* - This is a fundamental criterion for measles elimination, signifying that **endemic transmission has been interrupted** for at least 12 months in the presence of a well-performing surveillance system. - It means that any detected cases are either **imported** or linked to an imported source, without sustained local spread. *Incidence rate < 1 per million population* - This **epidemiological indicator** is the WHO-defined threshold to demonstrate that the interruption of endemic transmission (elimination) has been achieved and sustained. - A rate this low confirms that local transmission chains are either nonexistent or very short-lived due to high population immunity. *High vaccination coverage (>95%)* - Achieving and maintaining high vaccination coverage, especially with two doses of measles-containing vaccine, is crucial for establishing and sustaining **herd immunity**. - High coverage at both national and subnational levels is essential to prevent outbreaks and ensure the long-term success of elimination efforts.

Question 448: In a 10-year-old school child, which of the following vaccines is given as a part of the school immunization program?

A. Measles vaccine
B. Rotavirus vaccine
C. TT/Td vaccine (Correct Answer)
D. Hepatitis B vaccine

Explanation: ***TT/Td vaccine*** - The **tetanus toxoid (TT)** or **tetanus and diphtheria (Td) vaccine** is commonly administered to school-aged children as a booster to maintain immunity against these diseases. - This is part of many national immunization programs, including those in schools, to ensure continued protection beyond early childhood vaccinations. *Measles vaccine* - The **measles vaccine (MMR)** is typically given at 9-12 months and a second dose around 4-6 years of age, much earlier than 10 years. - While essential, it's usually completed before a child reaches the age of 10 for primary vaccination. *Rotavirus vaccine* - The **rotavirus vaccine** is administered to infants, usually before 6 months of age, to protect against severe rotavirus gastroenteritis. - It is not part of school immunization programs for 10-year-olds. *Hepatitis B vaccine* - The **Hepatitis B vaccine** is typically given at birth and completed during infancy, with a series of doses before 1 year of age. - While crucial for early protection, it is not a routine vaccination for 10-year-olds within a school immunization program unless for catch-up reasons.

Question 449: Which vaccine is recommended to be given every year?

A. Hepatitis A vaccine
B. Varicella (Chickenpox) vaccine
C. Influenza vaccine (Correct Answer)
D. Hepatitis B vaccine

Explanation: ***Influenza vaccine*** - The **influenza virus** constantly mutates, leading to new strains emerging each year. - Annual vaccination is recommended to provide protection against the most prevalent strains predicted for the upcoming flu season. - This is the only vaccine that requires yearly administration due to **antigenic drift**. *Hepatitis A vaccine* - The Hepatitis A vaccine provides **long-term immunity** after a two-dose series. - It does not require annual administration after the initial series is completed. *Varicella (Chickenpox) vaccine* - The Varicella vaccine (typically a two-dose series) offers **durable immunity** against chickenpox. - Annual vaccination is not necessary as protection typically lasts for many years. *Hepatitis B vaccine* - The Hepatitis B vaccine series (usually three doses) provides **long-lasting protection** against the Hepatitis B virus. - Routine annual boosters are not required for individuals who have completed the primary series.

Question 450: A patient with the following feature shown in the image. The patient reports having another 3-year-old sibling at home, who is fully immunized as per the immunization schedule. What is the best measure to prevent diphtheria in the sibling of the child with diphtheria?

A. Give diphtheria toxoid booster
B. Give a full course of DPT vaccine
C. Give prophylactic erythromycin (Correct Answer)
D. Nothing is required to be done

Explanation: ***Correct: Give prophylactic erythromycin*** - Erythromycin is the **recommended antimicrobial prophylaxis** for close contacts of diphtheria patients to eradicate *Corynebacterium diphtheriae* carriage. - This prevents asymptomatic carriers from transmitting the bacteria, even if vaccinated, as vaccination provides immunity against the toxin, not necessarily against carriage. *Incorrect: Give diphtheria toxoid booster* - While immunization reduces the risk of symptomatic diphtheria disease by inducing **antitoxin immunity**, it does not reliably prevent nasal or pharyngeal carriage of the bacteria. - A booster might be considered if the last dose was more than 5 years ago, but it is not the primary immediate measure to prevent transmission from a known contact. *Incorrect: Give a full course of DPT vaccine* - The patient's sibling is already reported to be **fully immunized**, implying they have received the appropriate doses of the DPT vaccine according to the immunization schedule. - Giving a full course when already immunized would be redundant and ineffective to prevent immediate exposure and potential carriage. *Incorrect: Nothing is required to be done* - Close contacts of diphtheria cases are at **high risk of acquiring and transmitting the infection**, even if they are fully immunized, as immunization protects against the toxin but not necessarily carriage. - Failure to intervene would allow potential colonization and transmission, posing a risk to the community and the contact themselves.

Practice by Chapter

Principles of Immunization

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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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