Immunization and Vaccine-Preventable Diseases — MCQs

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

Question 401: Smallpox eradication was not due to:

A. Highly effective vaccine
B. Cross-immunity with animal pox virus (Correct Answer)
C. Subclinical infections do not transmit the disease
D. Life long immunity

Explanation: ***Cross-immunity with animal pox virus*** - While cowpox provided the basis for the smallpox vaccine, **cross-immunity with naturally circulating animal pox viruses** did not contribute to the eradication of smallpox itself. - The eradication was achieved through targeted vaccination campaigns with a **human-specific vaccine**, not by incidental cross-protection from wildlife. *Highly effective vaccine* - The smallpox vaccine was highly effective, providing **strong and long-lasting immunity** against the Variola virus. - This effectiveness was crucial for establishing herd immunity and breaking the chains of transmission. *Subclinical infections do not transmit the disease* - Individuals infected with smallpox either developed **symptomatic disease** or were **immune/resistant** to infection. - The absence of asymptomatic carriers who could silently transmit the virus made it feasible to interrupt transmission through targeted vaccination and surveillance. *Life long immunity* - Both natural infection and successful vaccination provided **long-lasting, often lifelong immunity** to smallpox. - This durable immunity prevented reinfection and helped sustain the protection achieved through vaccination campaigns over time.

Question 402: Best means of giving hepatitis B vaccine is

A. Intramuscular deltoid (Correct Answer)
B. Intradermal
C. Subcutaneous
D. Intramuscular gluteal

Explanation: ***Intramuscular deltoid*** - The **deltoid muscle** is the recommended site for hepatitis B vaccine administration in adults and older children due to its muscle mass and distance from major nerves and vessels. - This route ensures proper absorption and immunogenicity, leading to an optimal **antibody response**. *Intradermal* - This route is typically reserved for vaccines that require a small dose and a localized immune response, such as the **BCG vaccine**. - It's not recommended for hepatitis B vaccine as it can lead to reduced efficacy and a less robust immune response. *Subcutaneous* - **Subcutaneous administration** might be considered in individuals with bleeding disorders, but it generally leads to a less consistent and potentially weaker immune response for hepatitis B vaccination. - It's a second-line route when intramuscular injection is contraindicated, not the primary method. *Intramuscular gluteal* - The **gluteal muscle** is not the preferred site for vaccines due to the risk of injury to the **sciatic nerve** and the potential for injection into adipose tissue rather than muscle, which can compromise vaccine efficacy. - While intramuscular, absorption can be less predictable compared to the deltoid, especially in adults.

Question 403: Tetracycline ointment concentration recommended for mass prophylaxis in trachoma control programs is:

A. 5%
B. 0.10%
C. 1% (Correct Answer)
D. 0.50%

Explanation: ***1% (Correct Answer)*** - **Tetracycline 1% ophthalmic ointment** is the WHO-recommended standard concentration for mass prophylaxis in trachoma control programs [1] - Effective in reducing the prevalence of ocular *Chlamydia trachomatis* infection in endemic areas [1] - Part of the SAFE strategy (Surgery, Antibiotics, Facial cleanliness, Environmental improvement) for trachoma elimination *5% (Incorrect)* - This concentration is **not the recommended standard** for mass prophylaxis of trachoma - Higher concentrations are typically unnecessary and could potentially increase the risk of local irritation without providing significant additional benefit - No evidence supporting superiority over the 1% formulation *0.10% (Incorrect)* - This concentration would be **too low** for effective mass prophylaxis of trachoma - Insufficient to achieve therapeutic levels needed to eliminate *Chlamydia trachomatis* in a population - Would not meet WHO guidelines for trachoma control *0.50% (Incorrect)* - This concentration is **lower than the recommended 1%** for mass prophylaxis - While it might have some activity, it is considered **suboptimal** for achieving population-level control of trachoma - Not supported by evidence-based guidelines for trachoma elimination programs

Question 404: Which of the following is a currently recommended vaccine for rabies post-exposure prophylaxis?

A. Duck embryo vaccine
B. Semple
C. Suckling mouse brain vaccine
D. HDCV (Correct Answer)

Explanation: ***HDCV*** - **Human Diploid Cell Vaccine (HDCV)** is a modern, highly effective, and safe vaccine widely recommended for both pre-exposure and post-exposure rabies prophylaxis. - It is prepared with virus grown in **human diploid cell cultures**, ensuring higher purity and fewer side effects compared to older vaccines. *Duck embryo vaccine* - The duck embryo vaccine was an older type of rabies vaccine that is **no longer recommended** due to its lower potency and higher incidence of adverse reactions. - It was derived from inactivated rabies virus grown in **duck embryos**. *Semple* - The Semple vaccine, also known as the **nervous tissue vaccine**, was historically significant but is now **obsolete** because of severe neurological complications associated with its use. - It was prepared from the brains of rabies-infected animals and contained **myelin basic protein**, leading to encephalitis in some recipients. *Suckling mouse brain vaccine* - The suckling mouse brain vaccine was another older vaccine that is **no longer recommended** in many countries. - While an improvement over Semple, it still carried a risk of **neurological side effects** due to residual neural tissue components.

Question 405: True regarding pertussis vaccine is:

A. Leucocytosis is diagnostic
B. 95% of vaccinated individuals are protected
C. Neuroparalytic complication is seen in 1 in 15,000
D. Erythromycin should be given to contacts (Correct Answer)

Explanation: ***Erythromycin should be given to contacts*** - **Erythromycin** or other macrolides are recommended for close contacts of pertussis patients to prevent secondary cases, especially in vulnerable populations. - This **post-exposure prophylaxis** helps to eradicate *Bordetella pertussis* from the nasopharynx, reducing transmission. *Leucocytosis is diagnostic* - While **leukocytosis** with **lymphocytosis** is characteristic of pertussis, especially in infants, it is a supportive finding rather than definitively diagnostic on its own. - **PCR testing** or culture of nasopharyngeal secretions is required for definitive diagnosis. *95% of vaccinated individuals are protected* - The effectiveness of pertussis vaccines (DTaP and Tdap) is generally high, but it is typically around **80-85%**, not 95%, and **waning immunity** is common over time. - Protection is not absolute, and vaccinated individuals can still contract pertussis, although usually in a milder form. *Neuroparalytic complication is seen in 1 in 15,000* - **Serious adverse events** like encephalopathy or neuroparalytic complications following pertussis vaccination are **extremely rare**, with estimates much lower than 1 in 15,000. - Most reactions are mild and localized, such as pain or swelling at the injection site.

Question 406: A 30-year-old man reports 4 hours after acquiring a clean wound without laceration. He had received TT vaccination 10 years back. What do you advise regarding tetanus prophylaxis?

A. No vaccination needed
B. 1 dose of TT AND TIG
C. full course of TT
D. single dose of TT (Correct Answer)

Explanation: ***single dose of TT*** - For a **clean wound** in a patient who received a **TT vaccination 10 years ago**, a single dose of **Tetanus Toxoid (TT)** is sufficient to boost immunity. - This patient's previous vaccination history provides a baseline immunity, and a booster ensures continued protection against tetanus. *No vaccination needed* - Even with a "clean" wound, if the last vaccination was 10 years ago, the patient's **antibody levels** might be insufficient for full protection against tetanus. - Tetanus is a serious, often fatal, disease, making prophylaxis crucial even for minor wounds. *1 dose of TT AND TIG* - **Tetanus immunoglobulin (TIG)** is reserved for **dirty or contaminated wounds** or for individuals with an **unknown or incomplete vaccination history**. - In this case, the wound is clean and the patient has prior vaccination, so TIG is not indicated. *full course of TT* - A **full course of TT** (multiple doses) is typically recommended for individuals with an **unknown or incomplete vaccination history** to establish primary immunity. - Since this patient had a vaccination 10 years ago, they already possess foundational immunity, and only a booster is required.

Question 407: Protective level of Tetanus anti-toxin is:

A. >0.01 IU/mL (Correct Answer)
B. >0.5 IU/mL
C. >5 IU/mL
D. >1.0 IU/mL

Explanation: ***>0.01 IU/mL*** - A serum level of antibodies **greater than 0.01 IU/mL** is generally considered the **minimum protective level** against tetanus. - This threshold indicates sufficient immunity to prevent clinical tetanus, though higher levels offer an increased margin of protection. *>0.5 IU/mL* - While levels **above 0.5 IU/mL** indicate strong, long-lasting protection, they are not the minimum protective threshold. - This level is often considered indicative of **excellent immunity** that may last for many years. *>5 IU/mL* - A level of **5 IU/mL** or higher signifies a very high antibody titer, far exceeding the basic protective level. - This level is not the standard for basic protection and often seen after **recent vaccination** or booster. *>1.0 IU/mL* - Levels **above 1.0 IU/mL** indicate very good protection, but this is a higher threshold than the minimal protective level. - It suggests a robust immune response, but not the absolute lowest concentration required for immunity.

Question 408: A 2-year-old child diagnosed provisionally with diphtheria and on examination she has greyish white membrane patch around her tonsils. The child has a 6-year-old sibling at home, who is fully immunized as per the schedule. What is the best measure to prevent disease in the sibling of the child?

A. Prophylactic erythromycin to be given (Correct Answer)
B. Nothing is required to be done
C. Full course of DPT
D. Booster dose of DPT

Explanation: ***Prophylactic erythromycin to be given*** - All **close contacts** of a diphtheria patient, regardless of their immunization status, should receive **antibiotic prophylaxis** to eliminate carriage of *C. diphtheriae*. - **Erythromycin** is a commonly recommended antibiotic for this purpose, given its effectiveness against the bacteria. *Nothing is required to be done* - This is incorrect because, even if immunized, a close contact can still be a **carrier** of *C. diphtheriae* and transmit the infection to others. - **Diphtheria toxin** can still be produced by carriers, posing a risk of disease development if not cleared. *Full course of DPT* - This is unnecessary for a fully immunized child; a full course is typically for **unimmunized** or **incompletely immunized** - **Antibiotic prophylaxis** is the immediate priority for preventing illness in contacts. *Booster dose of DPT* - A booster dose offers **active immunity** but does not immediately address potential asymptomatic carriage of *C. diphtheriae*. - The primary goal for a contact is to eliminate the bacteria, which antibiotics can achieve more rapidly.

Question 409: In an epidemic of poliomyelitis, the best way to stop spread is by -

A. OPV drops to all children (Correct Answer)
B. Isolation of cases
C. Chlorination of all wells
D. Injection of killed vaccine

Explanation: ***OPV drops to all children*** - **Oral Polio Vaccine (OPV)** contains live, attenuated virus that replicates in the gut and provides both individual immunity and **herd immunity** by shedding modified virus, thus reducing transmission in an epidemic. - Administering OPV to all children during an epidemic is crucial because it quickly boosts population immunity and **blocks the fecal-oral transmission** pathway of the poliovirus. *Isolation of cases* - While isolation of affected individuals can reduce spread for some diseases, **poliovirus** can be shed asymptomatically for weeks, making isolation alone an ineffective strategy for epidemic control. - Poliovirus transmission is primarily through the **fecal-oral route**, and asymptomatic carriers can continue to spread the infection, undermining isolation efforts. *Chlorination of all wells* - **Chlorination of water sources** is important for general public health and preventing waterborne diseases, but it is not the most effective primary intervention for stopping an established polio epidemic. - While polio can be waterborne, **person-to-person fecal-oral transmission** is the dominant route, which is not directly addressed by water chlorination. *Injection of killed vaccine* - The **inactivated polio vaccine (IPV)**, given by injection, provides excellent individual immunity to paralytic polio but induces less intestinal immunity compared to OPV. - Due to lower intestinal immunity, IPV recipients can still replicate and shed the virus in their gut, potentially continuing **environmental transmission** during an epidemic, making it less effective for immediate epidemic control compared to OPV.

Question 410: What is the eight-site rabies vaccine schedule?

A. 0, 3, 7, 14, 28
B. 0-3-7
C. 8-4-0-1
D. 8-4-1-1 (Correct Answer)

Explanation: ***8-4-1-1*** - The **eight-site rabies vaccine schedule** refers to the **Thai Red Cross intradermal (2-1-1) regimen** which uses reduced vaccine volume per dose. - **8 sites on day 0** (0.1 ml intradermally at 8 sites), **4 sites on day 7** (0.1 ml at 4 sites), **1 site on day 21** (0.1 ml), and **1 site on day 28** (0.1 ml) - This schedule is cost-effective and WHO-approved for post-exposure prophylaxis - The "eight-site" terminology refers to the 8 injection sites used on day 0 *0, 3, 7, 14, 28* - This is the standard **5-dose intramuscular (Essen) regimen** for rabies post-exposure prophylaxis, not the eight-site intradermal regimen - It involves five 1.0 ml IM doses administered on days 0, 3, 7, 14, and 28 *0-3-7* - This is the **3-dose intramuscular schedule** used for pre-exposure prophylaxis or as an abbreviated post-exposure schedule in previously immunized individuals - It does not represent the eight-site intradermal regimen *8-4-0-1* - This option does not correspond to any recognized rabies vaccination schedule - The correct eight-site schedule is 8-4-1-1 (on days 0, 7, 21, and 28)

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

Want unlimited practice?

Get full access to all questions, explanations, and performance tracking.

Start For Free