Immunization and Vaccine-Preventable Diseases Practice Questions

Q: Which vaccine is used to prevent cholera?

WC-rBS. ***WC-rBS*** * **WC-rBS** stands for **whole-cell, recombinant B subunit** vaccine, also known as **Dukoral**. * It is an **oral inactivated vaccine** containing killed *Vibrio cholerae* O1 bacteria and the recombinant B subunit of the cholera toxin, providing immunity against cholera. * **WC-rBS is the WHO-prequalified cholera vaccine** widely used in India and recommended for travellers and in epidemic settings. * It provides protection against both O1 and O139 serogroups and offers some cross-protection against ETEC (enterotoxigenic *E. coli*). *CVD 103-HgR* * **CVD 103-HgR** (commercially known as **Vaxchora**) is an **oral live-attenuated cholera vaccine** approved by the FDA. * It is a genetically modified *Vibrio cholerae* O1 Inaba strain with deleted cholera toxin genes. * While this is also a cholera vaccine, **it is primarily used in the United States** and is not the standard vaccine used in India or recommended by WHO for mass vaccination campaigns. * In the Indian context and for NEET-PG examinations, **WC-rBS (Dukoral) is the recognized cholera vaccine**. *Ty21a* * **Ty21a** is an **oral live-attenuated vaccine** used to prevent **typhoid fever**. * It is specifically designed to target *Salmonella Typhi* bacteria, not *Vibrio cholerae*. *None of the options* * This option is incorrect because WC-rBS is the well-established and WHO-recommended vaccine for the prevention of cholera in the Indian context.

Q: Measles vaccination is given at -

9 months. ***9 months*** - The first dose of the **measles vaccine (MMR)** is typically administered at **9 months** of age in many national immunization programs. - This timing is chosen because maternal antibodies, which can interfere with vaccine effectiveness, generally wane by this age. *At birth* - Vaccines given at birth, such as **Hepatitis B** and **BCG**, target diseases with early exposure risks or have efficacy despite maternal antibodies. - Giving measles vaccine at birth would be ineffective due to the presence of **maternal antibodies** that neutralize the vaccine virus. *4 weeks* - This age is generally too early for measles vaccination as significant levels of **maternal antibodies** are often still present, which would reduce the vaccine's efficacy. - Other vaccines, like the rotavirus vaccine, might be given around this age, but not measles. *8 weeks* - While maternal antibodies might be decreasing, 8 weeks of age is still generally considered too early for optimal measles vaccine response. - Many primary vaccine series (e.g., DTaP, IPV, Hib) begin at 6-8 weeks, but measles is usually delayed further for better efficacy and seroconversion rates.

Q: What is the concentration of type 3 virus in the trivalent oral polio vaccine?

600,000 TCID 50. ***600,000 TCID 50*** - The **trivalent oral polio vaccine (tOPV)** traditionally contained specific concentrations of each serotype: **type 1 (1,000,000 TCID50/dose)**, **type 2 (100,000 TCID50/dose)**, and **type 3 (600,000 TCID50/dose)**. - Type 3 poliovirus requires a **higher concentration (600,000 TCID50)** compared to type 2 to achieve adequate immunogenicity and protection. - The **World Health Organization (WHO)** established these specific formulations for tOPV to ensure optimal efficacy and safety for each serotype. *100,000 TCID 50* - This is the concentration of **type 2 poliovirus** in tOPV, not type 3. - Due to the **global eradication of wild poliovirus type 2** by 2015, tOPV was replaced with bivalent OPV (bOPV) containing only types 1 and 3 in routine immunization programs. *400,000 TCID 50* - This concentration does not correspond to any standard poliovirus serotype in the traditional trivalent oral polio vaccine. - This value falls between type 2 (100,000) and type 3 (600,000) concentrations but is not used. *300,000 TCID 50* - This concentration is not the standard for any poliovirus serotype in the traditional trivalent oral polio vaccine. - Each serotype has a **distinct, empirically determined concentration** to achieve optimal immunity while minimizing adverse effects.

Q: In which of the following diseases is mass vaccination considered ineffective?

Tetanus. ***Correct: Tetanus*** - Mass vaccination is considered **ineffective** for tetanus because it is **not a communicable disease** transmitted person-to-person - Tetanus is caused by **Clostridium tetani** spores present in soil and environment - Since there is **no herd immunity** benefit, vaccinating large populations simultaneously does not break any chain of transmission - **Individual immunization** with tetanus toxoid is highly effective for personal protection, but this is different from mass vaccination strategies used for communicable diseases - The focus for tetanus prevention is on **universal immunization** and **wound management**, not mass campaigns *Incorrect: Measles* - Mass vaccination for measles is **highly effective** due to its person-to-person transmission - Achieving high vaccination coverage (>95%) provides **herd immunity** and can lead to **elimination** - The **MMR vaccine** is a cornerstone of mass immunization programs worldwide *Incorrect: Polio* - Mass vaccination campaigns (Pulse Polio) have been **extremely effective** in nearly eradicating polio globally - The disease spreads through the fecal-oral route, making mass vaccination crucial for breaking transmission chains - Both **OPV** and **IPV** provide individual and community protection through herd immunity *Incorrect: None of the options* - This is incorrect because tetanus is a clear example where mass vaccination strategy is ineffective due to lack of person-to-person transmission

Q: Which live vaccine is contraindicated in AIDS patients?

BCG. **BCG** - The **BCG vaccine** is a live attenuated vaccine, and due to the immunocompromised state of AIDS patients, there is a significant risk of developing disseminated BCG infection. - This risk is particularly high in individuals with **severe immunodeficiency** (low CD4 count), making it a strong contraindication. *Oral Polio Vaccine (OPV)* - While OPV is a live vaccine, it is generally considered safe in asymptomatic HIV-infected individuals, but contraindicated in **symptomatic AIDS patients** due to the risk of vaccine-associated paralytic poliomyelitis [1]. - However, in many regions, the inactivated polio vaccine (IPV) is preferred for all HIV-infected individuals to completely eliminate this risk. *Varicella (Chickenpox)* - The **varicella vaccine** is a live attenuated vaccine; however, it is generally recommended for HIV-infected children and adults who are not severely immunocompromised (CD4 count >200 cells/µL). - The benefits of preventing severe chickenpox often outweigh the risks of vaccination in these individuals. *Measles* - The **measles vaccine (MMR)** is a live attenuated vaccine and is generally recommended for HIV-infected individuals who are not severely immunocompromised (CD4 count >200 cells/µL). - The severe morbidity and mortality associated with measles in immunocompromised individuals prioritize vaccination when appropriate.

Q: Which of the following vaccines is NOT included in the National Immunization Schedule?

Human Papillomavirus (HPV). ***Human Papillomavirus (HPV)*** - **HPV vaccine is NOT part of India's routine Universal Immunization Programme (UIP)**, making it the correct answer. - While **pilot programs** have been conducted in some states and various bodies recommend it, HPV has **never been universally included** in India's national immunization schedule. *TT (Tetanus Toxoid)* - **TT is a core component** of India's UIP and is actively used in immunization programs. - Given to **pregnant women** (2 doses during pregnancy) and as **Td vaccine** at 10 and 16 years of age. *OPV (Oral Polio Vaccine)* - While **OPV was phased out** from India's UIP in 2016, it was **historically part** of the national schedule. - India switched to **Injectable Polio Vaccine (IPV)** to eliminate vaccine-derived polio risk, but OPV was previously included. *Measles* - **Measles vaccine is actively included** in India's UIP as part of the **MR (Measles-Rubella) vaccine**. - Administered at **9 months and 16-24 months** of age as part of routine immunization.

Q: Which of the following diseases currently lacks a widely available effective vaccine?

Dengue fever. ***Dengue fever*** - While there is a vaccine (Dengvaxia) available in some regions for specific populations, its use is restricted due to concerns about increased risk of severe dengue in **seronegative individuals**. - There is currently **no single, universally recommended, and widely available effective vaccine** for all populations against all serotypes of dengue, making dengue a disease greatly in need of better vaccination strategies. *Yellow fever* - A **highly effective and safe live-attenuated vaccine** against yellow fever has been available for many decades, providing long-lasting immunity. - It is a standard vaccine for travelers to endemic areas and part of routine immunization programs in many affected countries. *Japanese encephalitis* - Several effective vaccines against Japanese encephalitis are **widely available and recommended** for individuals living in or traveling to endemic regions. - These vaccines include inactivated and live-attenuated forms, offering significant protection against the disease. *Russian spring summer encephalitis* - An **effective inactivated vaccine** is available for Russian spring-summer encephalitis and is recommended for those at risk due to occupational exposure or travel to endemic areas. - Vaccination provides reliable protection against this tick-borne viral infection.

Q: Which of the following vaccines is not included in the Mission Indradhanush program?

Typhoid fever vaccine. ***Typhoid fever vaccine*** - The **typhoid conjugate vaccine (TCV)** was introduced into India's Universal Immunization Programme in a phased manner starting from 2017-2018, but it is **not part of the core Mission Indradhanush vaccines** launched in 2014. - Mission Indradhanush primarily focuses on the original set of vaccines for common, preventable childhood diseases (BCG, DPT, OPV, Hepatitis B, Measles, etc.), and later additions like Rotavirus and PCV. - TCV rollout has been **state-specific and phased**, unlike the universal coverage of core Mission Indradhanush vaccines. *Diphtheria* - The **diphtheria vaccine** is a core component of the Mission Indradhanush program, aiming to protect children against this serious bacterial infection. - It is administered as part of the **DPT (Diphtheria, Pertussis, Tetanus)** or **Pentavalent vaccine** (DPT + Hib + Hepatitis B). *Polio* - The **polio vaccine** is a primary target of Mission Indradhanush, as India has maintained its polio-free status since 2014. - It is given as **OPV (Oral Polio Vaccine)** and/or **IPV (Inactivated Polio Vaccine)** to prevent poliomyelitis. *Tetanus* - The **tetanus vaccine** is included in the Mission Indradhanush program, administered with diphtheria and pertussis as the **DPT vaccine** or as part of the **Pentavalent vaccine**. - It protects against **tetanus**, a severe bacterial infection causing painful muscle spasms and lockjaw.

Q: Oral cholera vaccine is effective for:

3 years. ***3 years*** - **Oral cholera vaccines** like Shanchol and Euvichol-Plus provide protection for at least **3 years** after complete 2-dose immunization. - Studies in endemic areas demonstrate sustained protection extending **up to 5 years** with Shanchol. - The **WHO recommends** OCVs as part of comprehensive cholera control strategies in endemic regions and outbreak settings. - This duration is based on field effectiveness studies and clinical trials in various populations. *2 years* - While **Dukoral** (another OCV) provides protection for approximately **2 years**, this is not the standard duration for the most widely used OCVs. - **2 years** represents the conservative lower estimate, not the established duration for Shanchol/Euvichol vaccines. - Current evidence supports longer protection than 2 years for most recipients. *12 months* - **12 months** significantly underestimates the protective duration of oral cholera vaccines. - All WHO-prequalified OCVs provide protection well beyond 1 year. - This duration might represent only the initial phase of immunity, not the full protective window. *6 months* - **6 months** is far too short and does not reflect the established efficacy of any current oral cholera vaccine. - While seroconversion occurs within weeks, the protective immunity lasts much longer. - No WHO-prequalified OCV has such a limited duration of protection.

Question 1

Which vaccine is used to prevent cholera?

Accepted Answer

WC-rBS

Answer

CVD 103-HgR

Answer

Ty21 A

Answer

None of the options

Question 2

Measles vaccination is given at -

Accepted Answer

9 months

Answer

At birth

Answer

4 weeks

Answer

8 weeks

Question 3

What is the concentration of type 3 virus in the trivalent oral polio vaccine?

Accepted Answer

600,000 TCID 50

Answer

400,000 TCID 50

Answer

100,000 TCID 50

Answer

300,000 TCID 50

Question 4

In which of the following diseases is mass vaccination considered ineffective?

Accepted Answer

Tetanus

Answer

None of the options

Answer

Measles

Answer

Polio

Question 5

Which live vaccine is contraindicated in AIDS patients?

Accepted Answer

BCG

Answer

Measles

Answer

Varicella (Chickenpox)

Answer

Oral Polio Vaccine (OPV)

Question 6

What is the purpose of 'ring vaccination' in disease control?

Accepted Answer

Vaccination administered within a specific radius around a confirmed case.

Answer

A strategy to create lesions for disease identification.

Answer

Vaccination given to all individuals in a one-mile radius of a case.

Answer

A mass vaccination campaign targeting the entire population of a region.

Question 7

Which of the following vaccines is NOT included in the National Immunization Schedule?

Accepted Answer

Human Papillomavirus (HPV)

Answer

TT

Answer

OPV

Answer

Measles

Question 8

Which of the following diseases currently lacks a widely available effective vaccine?

Accepted Answer

Dengue fever

Answer

Japanese encephalitis

Answer

Russian spring summer encephalitis

Answer

Yellow fever

Question 9

Which of the following vaccines is not included in the Mission Indradhanush program?

Accepted Answer

Typhoid fever vaccine

Answer

Diphtheria

Answer

Polio

Answer

Tetanus

Question 10

Oral cholera vaccine is effective for:

Accepted Answer

3 years

Answer

6 months

Answer

12 months

Answer

2 years

Immunization and Vaccine-Preventable Diseases — MCQs

Immunization and Vaccine-Preventable Diseases — MCQs

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