Immunization and Vaccine-Preventable Diseases — MCQs

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

Question 411: Incubation period of pertussis is-

A. 7-14 days (Correct Answer)
B. More than 28 days
C. 15-28 days
D. 1-7 days

Explanation: ***7-14 days*** - The typical incubation period for **pertussis**, or whooping cough, caused by **_Bordetella pertussis_**, is usually **7 to 14 days**, though it can range from 6 to 20 days. - This period is the time from exposure to the **onset of initial symptoms**, such as a runny nose and mild cough. *More than 28 days* - An incubation period of **more than 28 days** is uncharacteristic for pertussis, as symptoms typically manifest much sooner. - Such a long delay in symptom onset would suggest a different infectious agent or a different disease entirely. *15-28 days* - While up to 20 days is possible, an incubation period predominantly in the **15-28 day range** is less common for pertussis, with most cases presenting earlier. - This longer range is more characteristic of other infections like **hepatitis B** or **HIV**. *1-7 days* - An incubation period of **1-7 days** is generally too short for pertussis, which typically requires a longer time for bacterial replication and symptom development. - Shorter incubation periods are more typical for diseases caused by rapidly replicating pathogens or toxins, such as **influenza** or **food poisoning**.

Question 412: Most common route of administration for inactivated influenza vaccine

A. Intranasal
B. Subcutaneous
C. Oral
D. Intramuscular (Correct Answer)

Explanation: ***Intramuscular*** - Most **inactivated influenza vaccines (IIV)** are administered via the **intramuscular route**. - This route ensures effective delivery of the vaccine antigens to muscle tissue, where a strong **systemic immune response** can be generated. - The **deltoid muscle** is the preferred site for adults and older children. *Intranasal* - The **live attenuated influenza vaccine (LAIV)**, not the inactivated vaccine, is administered intranasally. - This route is used for LAIV to mimic natural infection and induce both systemic and **mucosal immunity**. - Intranasal route is **not used** for inactivated influenza vaccines. *Subcutaneous* - The **subcutaneous route** is not the standard route for inactivated influenza vaccines. - While it can be used in certain circumstances (e.g., patients with bleeding disorders), **intramuscular injection** is the preferred and most common route. *Oral* - **Oral administration** is not used for influenza vaccines. - This route is typically reserved for vaccines that need to elicit a strong **mucosal immune response** in the gut (e.g., oral polio vaccine, rotavirus vaccine).

Question 413: Which of the following about the Sabin vaccine is not true?

A. It is given intramuscularly (Correct Answer)
B. It contains all the 3 strains of polio virus
C. Three doses are given for primary immunization
D. It is given at intervals of 4-6 weeks

Explanation: ***It is given intramuscularly*** - The **Sabin vaccine** (Oral Polio Vaccine, OPV) is administered **orally**, not intramuscularly. - This route of administration allows it to induce **mucosal immunity** in the gut, which is crucial for blocking wild poliovirus transmission. *It is given at intervals of 4-6 weeks* - This statement is generally true; **OPV doses** are often given with an interval of 4-6 weeks to build robust immunity. - These intervals optimize the **immune response** to each dose of the live attenuated virus. *It contains all the 3 strains of polio virus* - Historically, the **trivalent Sabin vaccine** contained live attenuated forms of all three poliovirus serotypes (Types 1, 2, and 3). - However, due to the eradication of **wild poliovirus type 2**, many current formulations are now **bivalent** (containing types 1 and 3). *Three doses are given for primary immunization* - A primary course of **three doses** of Sabin vaccine is typically recommended for full protection against poliovirus. - This schedule ensures comprehensive and long-lasting **immunization**.

Question 414: Typhoid Vi polysaccharide vaccine is usually administered in children above the age of :

A. 1 year 6 months
B. 1 year
C. 2 years (Correct Answer)
D. 6 months

Explanation: ***2 years*** - The **Typhoid Vi polysaccharide vaccine** is generally recommended for children starting at **2 years of age** because younger children may have a suboptimal immune response to polysaccharide vaccines. - This age limit helps ensure better **immunogenicity** and protection in the vaccinated child. *1 year 6 months* - While some vaccines are given around this age, the **Typhoid Vi polysaccharide vaccine** is not typically administered at **1 year 6 months** due to concerns about vaccine efficacy in very young children. - Administering it before **2 years** may lead to a less robust and protective immune response. *1 year* - **One-year-olds** generally do not respond as effectively to **polysaccharide vaccines** as older children. - The immune system matures, and the response to this specific type of vaccine improves significantly after the age of **2 years**. *6 months* - Vaccinating an infant at **6 months** with the **Typhoid Vi polysaccharide vaccine** is not recommended. - The immune system of an infant at this age is still developing and would likely produce an inadequate and **short-lived immune response** to this vaccine.

Question 415: Commonest age group for diphtheria is -

A. 6-10 Years
B. 1-2 Years
C. 1-5 Years (Correct Answer)
D. 5-10 Years

Explanation: ***1-5 Years*** - Diphtheria primarily affects children due to their developing immune systems and higher exposure risk in communities. - This age group is particularly vulnerable before completing their full vaccination series or if vaccination coverage is low. *6-10 Years* - While diphtheria can occur in this age group, it is less common than in younger children due to increased immunity from prior exposure or vaccination. - Most children would have received several doses of the diphtheria vaccine by this age. *1-2 Years* - This age group is susceptible to diphtheria, but the peak incidence typically extends beyond 2 years, encompassing the preschool years. - The risk remains high in this age group, but the broader 1-5 year range captures the highest prevalence. *5-10 Years* - This age range includes some of the peak years for diphtheria, but the highest incidence is generally observed earlier, between 1 and 5 years, before substantial booster immunity is achieved. - The susceptibility decreases with increasing age as immunity builds up.

Question 416: As per the Indian immunization schedule (IAP), at what age is the Hepatitis A vaccine recommended?

A. 2 years
B. 5 years
C. 1 year (Correct Answer)
D. 10 years

Explanation: ***1 year*** - The **Hepatitis A vaccine** is recommended as a 2-dose series for all children, with the first dose typically administered between **12 and 23 months of age**. - This timing ensures early protection against **Hepatitis A virus infection**, which can cause liver inflammation. *2 years* - While some vaccinations might be administered around this age, the **initial dose of hepatitis A** is generally given earlier. - Delaying the first dose until 2 years would miss the recommended primary vaccination window for most children. *5 years* - By 5 years of age, children should have already completed their **Hepatitis A vaccine series**. - Vaccination at this age would only be for those who somehow missed the recommended earlier doses. *10 years* - The Hepatitis A vaccine is not primarily recommended at 10 years of age for routine childhood immunization. - Vaccination at this age would typically only occur if a child had not previously received the vaccine, often due to travel to endemic areas or other specific risk factors.

Question 417: Which vaccine requires annual updates due to frequent antigenic changes?

A. Measles
B. Rubella
C. Influenza (Correct Answer)
D. BCG

Explanation: ***Influenza*** - The influenza virus undergoes frequent **antigenic drift** and **antigenic shift**, which are changes in its surface proteins (hemagglutinin and neuraminidase). - These constant changes necessitate annual updates to the influenza vaccine to match the circulating strains predicted for the upcoming flu season. *Measles* - The measles virus is **antigenically stable**, meaning it does not frequently change its surface proteins. - Due to its stability, a highly effective and long-lasting vaccine can be produced, and annual updates are not required. *Rubella* - The rubella virus is also **antigenically stable**, similar to measles. - A single vaccine, usually given as part of the MMR (Measles, Mumps, Rubella) vaccine, provides long-term immunity without the need for annual revision. *BCG* - The Bacillus Calmette-Guérin (BCG) vaccine targets *Mycobacterium tuberculosis* and is not subject to frequent antigenic changes. - It is a live-attenuated vaccine that provides long-lasting immunity, and annual boosters or updates are not necessary.

Question 418: A 5-year-old unimmunized child developed diphtheria. He has a 3-year-old immunized sibling contact, who received the last booster 18 months back. What should be done with the contact?

A. No vaccine needed
B. Three doses of conjugate vaccine
C. Two doses of polysaccharide vaccine
D. Single dose of toxoid vaccine (Correct Answer)

Explanation: ***Single dose of toxoid vaccine*** - In the context of this question, this is the **best available option** among the choices provided. - For a close contact of diphtheria who was immunized but received their last booster **18 months ago**, guidelines recommend a **booster dose if more than 5 years** have elapsed since the last dose. - However, some protocols recommend a booster for **close contacts regardless of timing** to ensure maximum protection. - **Important note**: The PRIMARY management for diphtheria close contacts is **antibiotic prophylaxis** (Erythromycin 40-50 mg/kg/day for 7 days or single-dose Azithromycin) plus surveillance for 7 days, which is not mentioned in the available options. *No vaccine needed* - This is incorrect because as a **close contact of an active diphtheria case**, prophylactic measures are required. - Even though the child received a booster 18 months ago, additional protection through either antibiotics (primary) or a booster dose may be recommended. - Close contacts require active intervention to prevent secondary transmission. *Three doses of conjugate vaccine* - This represents a **complete primary series**, which is not appropriate for an already immunized child. - The child has already completed primary immunization and received boosters; they do not need to restart the vaccination schedule. - **Conjugate vaccines** (like Hib conjugate) are different formulations, though DTaP is technically a conjugated form of diphtheria toxoid. *Two doses of polysaccharide vaccine* - **Polysaccharide vaccines** are not used for diphtheria prevention. - Diphtheria vaccines are **toxoid-based** (inactivated diphtheria toxin), not polysaccharide-based. - This option represents an incorrect vaccine type for diphtheria prophylaxis.

Question 419: BCG is maximally protective against:

A. CNS and Disseminated TB (Correct Answer)
B. Pulmonary TB
C. Extra pulmonary TB
D. Pulmonary and CNS TB

Explanation: ***CNS and Disseminated TB*** - **BCG vaccination** is highly effective in preventing severe forms of tuberculosis, specifically **meningeal TB** (a form of CNS TB) and **disseminated TB** (miliary TB) in children. - While it doesn't offer complete protection against all forms of TB, its efficacy is greatest against these life-threatening manifestations. *Pulmonary TB* - BCG offers only **modest protection** against **pulmonary TB** in adults, and its effectiveness varies significantly depending on the population and geographical location. - The vaccine's primary benefit is not in preventing typical adult pulmonary disease. *Extra pulmonary TB* - Although **CNS and disseminated TB** are forms of extrapulmonary TB, BCG's protection against other extrapulmonary manifestations (e.g., lymph node TB, bone TB) is generally **less robust** than its protection against CNS and disseminated forms. - The term "extra pulmonary TB" is too broad; BCG's highest efficacy is specific to the most severe forms. *Pulmonary and CNS TB* - While BCG is effective against **CNS TB**, it offers only **limited protection** against **pulmonary TB**. - Combining these two forms overstates its overall efficacy against pulmonary disease.

Question 420: Which of the following does not include Specific protection under primary prevention?

A. Health education (Correct Answer)
B. Tab Rifampicin to those in contact with meningitis
C. Wheat flour fortified with added iron
D. Pentavalent vaccination

Explanation: ***Health education*** - **Health education** is a component of **health promotion**, which falls under the broader category of primary prevention. - While it aims to prevent disease, it focuses on general well-being and lifestyle changes rather than specific disease protection measures. *Tab Rifampicin to those in contact with meningitis* - This is an example of **chemoprophylaxis**, a form of **specific protection**. - It involves administering medication to prevent a specific infectious disease in individuals exposed to it. *Wheat flour fortified with added iron* - This represents **nutritional interventions** aimed at preventing specific deficiencies, thus falling under **specific protection**. - **Food fortification** provides micronutrients to prevent deficiencies like **iron-deficiency anemia**. *Pentavalent vaccination* - **Vaccination** is a classic example of **specific protection** as it targets specific infectious agents to prevent disease. - The **pentavalent vaccine** protects against five specific diseases: **diphtheria, tetanus, pertussis, Haemophilus influenzae type b, and hepatitis B**.

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

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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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