Immunization and Vaccine-Preventable Diseases — MCQs

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

Question 11: Which of the following is NOT a characteristic of the polio vaccine?

A. Maintenance of cold chain is crucial.
B. Achieving 100% immunization coverage is a characteristic. (Correct Answer)
C. The killed vaccine is effective in India.
D. Five doses of OPV are administered.

Explanation: ### Explanation The correct answer is **B**, as achieving 100% immunization coverage is **not** a characteristic of the polio vaccine itself, nor is it a prerequisite for the success of the polio eradication strategy. **1. Why Option B is the correct answer (The "Not" characteristic):** In public health, the concept of **Herd Immunity** (Community Immunity) is central to polio eradication. For polio, it is estimated that if approximately **80-85%** of the population is immunized, the chain of transmission is broken, protecting even the unimmunized individuals. Therefore, 100% coverage is neither a biological characteristic of the vaccine nor a requirement for disease control. **2. Analysis of Incorrect Options:** * **Option A:** OPV is the most heat-sensitive vaccine in the UIP. It must be stored at **-20°C** (at the district level) and **+2°C to +8°C** (at PHCs). The **Vaccine Vial Monitor (VVM)** is used specifically to ensure the cold chain is maintained. * **Option C:** The Inactivated Polio Vaccine (IPV/Killed) is highly effective. In India, it was introduced into the routine immunization schedule (fractional doses at 6, 14 weeks, and 9 months) to provide systemic immunity and mitigate the risk of Vaccine-Associated Paralytic Polio (VAPP). * **Option D:** Under the National Immunization Schedule, a child receives 5 doses of OPV: a **Zero dose** at birth, three primary doses (6, 10, 14 weeks), and a **Booster dose** (16-24 months). **High-Yield NEET-PG Pearls:** * **Most Heat Sensitive Vaccine:** OPV (requires strict cold chain). * **Most Heat Resistant Vaccine:** Tetanus Toxoid (TT). * **VVM:** Focuses on heat exposure; if the inner square matches or is darker than the outer circle, the vaccine is discarded. * **Herd Immunity:** Polio and Measles require high herd immunity, whereas **Tetanus** has no herd immunity (as it is not transmitted person-to-person). * **Eradication:** India was declared Polio-free by the WHO on March 27, 2014.

Question 12: Two girls in the same class are diagnosed with meningococcal meningitis. Their 12-year-old close friend is in fear of contracting the disease. What advice should be given to her?

A. Two doses of polysaccharide vaccine
B. Two doses of conjugate vaccine (Correct Answer)
C. Single dose of meningococcal vaccine
D. No vaccine needed as exposure has already occurred

Explanation: ### Explanation **1. Why Option B is Correct:** Meningococcal meningitis is highly contagious among close contacts (e.g., classmates). In an outbreak or high-risk exposure scenario, immunization is recommended alongside chemoprophylaxis. For adolescents (aged 11–18 years), the **Meningococcal Conjugate Vaccine (MCV4)** is the preferred choice. The standard schedule for this age group involves a **two-dose regimen**: a primary dose followed by a booster dose (usually after an interval of 5 years, or earlier if the risk persists). Conjugate vaccines are superior because they induce T-cell dependent immunity, provide longer-lasting protection, and reduce nasopharyngeal carriage, thereby contributing to herd immunity. **2. Why Other Options are Incorrect:** * **Option A:** Polysaccharide vaccines (MPSV4) are T-cell independent. they do not produce immunological memory, have shorter durations of protection, and are generally reserved for adults over 55 or when conjugate vaccines are unavailable. * **Option C:** While a single dose provides some protection, the current clinical guidelines for sustained immunity in adolescents emphasize the two-dose schedule (Primary + Booster) to prevent breakthrough infections. * **Option D:** This is incorrect because post-exposure vaccination, when combined with chemoprophylaxis (like Rifampicin or Ciprofloxacin), significantly reduces the risk of secondary cases in close contacts. **3. NEET-PG High-Yield Pearls:** * **Chemoprophylaxis of Choice:** **Rifampicin** (5-10 mg/kg) is the drug of choice for close contacts. Alternatives include Ciprofloxacin (single dose) or Ceftriaxone. * **Vaccine Types:** Conjugate vaccines (MCV4) cover serogroups A, C, Y, and W-135. Serogroup B requires a separate recombinant vaccine. * **Incubation Period:** Typically 2–10 days; droplet precautions are mandatory for the first 24 hours of antibiotic therapy. * **Most Common Serogroup in India:** Historically, Serogroup A has been responsible for major outbreaks in the "Meningitis Belt" and India.

Question 13: Which of the following is NOT a live attenuated vaccine?

A. Tuberculosis (BCG)
B. Typhoid
C. Varicella Zoster virus
D. Cholera (Correct Answer)

Explanation: **Explanation:** The correct answer is **Cholera**. In the context of immunization, vaccines are broadly classified into live attenuated, killed (inactivated), toxoids, and subunit vaccines. **Why Cholera is the correct answer:** The standard vaccines used for Cholera (such as **Dukoral** or **Shanchol**) are **killed (inactivated) whole-cell vaccines**, sometimes combined with a recombinant B-subunit of the cholera toxin. While an oral live attenuated cholera vaccine (Vaxchora) exists, it is not the primary form used in routine public health practice or the standard reference for exams unless specified. Therefore, among the given options, Cholera is categorized as a killed vaccine. **Analysis of incorrect options:** * **BCG (Tuberculosis):** This is a classic **live attenuated** bacterial vaccine derived from *Mycobacterium bovis*. * **Typhoid:** While an injectable killed vaccine (Vi polysaccharide) exists, the **Ty21a** oral vaccine is a widely used **live attenuated** formulation. In MCQ patterns, Typhoid is frequently used to represent the live attenuated category. * **Varicella Zoster:** This is a **live attenuated** viral vaccine (Oka strain) used to prevent chickenpox. **NEET-PG High-Yield Pearls:** * **Mnemonic for Live Vaccines:** "**B**oy **R**omeo **G**ive **M**y **L**ove **S**picy **V**ictory **T**onight" (**B**CG, **R**ota, **G**uinea pig/OPV, **M**MR, **L**eishmania, **S**mallpox, **V**aricella/Yellow Fever, **T**yphoid Ty21a). * **Rule of Thumb:** Live vaccines are generally contraindicated in pregnancy and severely immunocompromised individuals. * **BCG Fact:** It is the only live bacterial vaccine in the National Immunization Schedule of India given at birth.

Question 14: What is the correct procedure for handling a frozen DPT vaccine before use?

A. Shaken thoroughly before use
B. Allowed to melt before use
C. Discarded (Correct Answer)
D. Brought to room temperature before use

Explanation: **Explanation:** The correct procedure for handling a frozen DPT vaccine is to **discard it immediately**. **1. Why "Discarded" is correct:** DPT is an **adsorbed vaccine** (containing aluminum salts as adjuvants). When these vaccines are frozen, the aluminum adjuvant crystallizes, forming sharp aggregates. These crystals physically damage the antigen and permanently alter the vaccine's physical structure. This leads to two major issues: * **Loss of Potency:** The vaccine becomes significantly less effective. * **Increased Reactogenicity:** The crystallized particles can cause severe local reactions (sterile abscesses) at the injection site. **2. Why other options are incorrect:** * **Shaken thoroughly (A):** While the "Shake Test" is used to *check* if a vaccine was previously frozen, shaking a known frozen vaccine cannot reverse the structural damage to the adjuvant. * **Allowed to melt (B) / Brought to room temperature (D):** The damage caused by freezing is irreversible. Thawing the vaccine does not restore its potency or safety. **3. High-Yield Clinical Pearls for NEET-PG:** * **The Shake Test:** This is a validated field test used to determine if an adsorbed vaccine (DPT, DT, TT, Hep B, Pentavalent) has been damaged by freezing. If the "suspect" vial settles faster than a "control" vial (never frozen), it has been damaged and must be discarded. * **T-series Vaccines:** Remember that all vaccines starting with 'T' (TT, Td) along with DPT, Hep B, and Pentavalent are **freeze-sensitive** and must be stored in the basket of the ILR (Ice-Lined Refrigerator), never in the freezer or touching the walls. * **Storage Temperature:** These vaccines should be maintained between **+2°C to +8°C**.

Question 15: Nonavalent HPV vaccine consists of which of the following HPV types?

A. HPV types 6, 11, 16, 18, 32, 34, 45, 52 and 58
B. HPV types 6, 11, 16, 18, 31, 33, 45, 52 and 58 (Correct Answer)
C. HPV types 6, 11, 16, 18, 31, 33, 46, 53 and 59
D. HPV types 6, 11, 16, 18, 31, 33, 46, 52 and 58

Explanation: **Explanation:** The **Nonavalent HPV vaccine (Gardasil 9)** is designed to provide broader protection against Human Papillomavirus (HPV) compared to its predecessors. It includes the four types found in the quadrivalent vaccine plus five additional high-risk oncogenic types. 1. **Low-risk types (Genital Warts):** Types **6 and 11** (responsible for ~90% of anogenital warts). 2. **High-risk types (Cervical Cancer):** Types **16 and 18** (responsible for ~70% of cervical cancers) plus types **31, 33, 45, 52, and 58** (which account for an additional 15-20% of cervical cancers). **Analysis of Options:** * **Option B (Correct):** Correctly identifies the nine types: 6, 11, 16, 18, 31, 33, 45, 52, and 58. * **Option A:** Incorrectly includes types 32 and 34. * **Option C:** Incorrectly includes types 46, 53, and 59. * **Option D:** Incorrectly includes type 46. **High-Yield Clinical Pearls for NEET-PG:** * **Vaccine Types:** * *Bivalent (Cervarix):* 16, 18. * *Quadrivalent (Gardasil):* 6, 11, 16, 18. * *Nonavalent (Gardasil 9):* 6, 11, 16, 18, 31, 33, 45, 52, 58. * **Dosage Schedule (IAP/WHO):** * 9–14 years: 2 doses (0, 6 months). * 15 years and older: 3 doses (0, 1-2, 6 months). * **Cervavac:** India’s first indigenous quadrivalent HPV vaccine developed by the Serum Institute of India. * **Target Age:** The primary target group is girls aged 9–14 years, before sexual debut.

Question 16: Which of the following is a live attenuated vaccine?

A. Measles
B. Rabies (Correct Answer)
C. Oral polio
D. Yellow fever

Explanation: The question as presented contains a factual error in the provided key. In medical microbiology and community medicine, **Rabies is a killed (inactivated) vaccine**, whereas Measles, Oral Polio (OPV), and Yellow Fever are classic examples of **live attenuated vaccines**. ### **Correct Concept & Explanation** Live attenuated vaccines contain a version of the living virus that has been weakened (attenuated) so it cannot cause disease in healthy people but can still induce a robust immune response. * **Options A, C, and D (Measles, OPV, Yellow Fever):** These are all **Live Attenuated Vaccines**. * **Measles:** Derived from the Edmonston-Zagreb strain. * **Oral Polio (Sabin):** Contains live attenuated strains of Poliovirus (Types 1 and 3). * **Yellow Fever:** Uses the 17D strain. * **Option B (Rabies):** This is a **Killed/Inactivated Vaccine**. Modern Rabies vaccines (like Cell Culture Vaccines - HDCV, PCECV) use inactivated viruses. Therefore, it is the "odd one out" if the question asks for a live vaccine. ### **High-Yield NEET-PG Clinical Pearls** * **Mnemonic for Live Vaccines:** "**B**oy **R**omeo **G**ive **M**y **L**ove **T**o **P**olice **S**tation" (**B**CG, **R**otavirus, **G**ermany Measles [Rubella], **M**easles/**M**umps, **L**ive Typhoid [Ty21a], **T**ularemia, **P**olio [Sabin], **S**mallpox/Yellow Fever). * **Contraindications:** Live vaccines are generally contraindicated in **pregnancy** and **immunocompromised** states (except HIV patients before the symptomatic stage for certain vaccines). * **Storage:** Most live vaccines are highly heat-sensitive and must be stored in the **Cold Chain** (usually +2°C to +8°C, though OPV is stored at -20°C for long-term). * **Yellow Fever:** It is the only vaccine for which an International Certificate of Vaccination is mandatory for travel to/from endemic zones.

Question 17: Which of the following statements is TRUE about acellular pertussis vaccine EXCEPT?

A. It is a toxoid.
B. It is superior to whole-cell pertussis vaccine (wP). (Correct Answer)
C. The acellular component confers the same immunity as the cellular one.
D. It can be administered as both primary and booster immunization.

Explanation: **Explanation:** The question asks for the **FALSE** statement regarding the acellular pertussis vaccine (aP). **1. Why Option B is the Correct Answer (The False Statement):** While the acellular pertussis vaccine (aP) has a significantly **better safety profile** (fewer febrile seizures and local reactions), it is **immunologically inferior** to the whole-cell vaccine (wP). The wP vaccine induces a robust Th1/Th17 immune response and provides longer-lasting protection. In contrast, aP-induced immunity wanes faster, leading to a resurgence of pertussis in many developed countries. Therefore, saying aP is "superior" is incorrect in the context of efficacy and duration of protection. **2. Analysis of Other Options:** * **Option A (True):** The aP vaccine is primarily composed of **purified inactivated pertussis toxin (toxoid)**, along with other antigens like filamentous hemagglutinin (FHA) and pertactin. * **Option C (True):** In terms of immediate seroconversion, the acellular components are designed to confer a similar level of initial protective immunity as the cellular vaccine, though the durability differs. * **Option D (True):** aP is used for both the primary series (as DTaP) and as a booster dose (as Tdap) in adolescents and adults. **Clinical Pearls for NEET-PG:** * **wP vs. aP:** wP is used in India’s Universal Immunization Programme (UIP) due to its higher efficacy and lower cost. * **Adverse Effects:** wP is associated with "Persistent Crying" and "Hypotonic Hyporesponsive Episodes" (HHE); aP is preferred in private practice to minimize these. * **Contraindication:** Any pertussis vaccine is contraindicated if the child develops **encephalopathy** within 7 days of a previous dose.

Question 18: Which vaccine is not useful in a patient with AIDS?

A. Oral Polio Vaccine (OPV) (Correct Answer)
B. Hepatitis B Vaccine
C. Bacillus Calmette-Guérin (BCG) Vaccine
D. Measles Vaccine

Explanation: **Explanation:** The core concept tested here is the safety of **Live Attenuated Vaccines** in immunocompromised individuals. In patients with AIDS (CD4 count <200 cells/mm³), live vaccines are generally contraindicated due to the risk of "vaccine-induced disease" caused by the uncontrolled replication of the attenuated pathogen. **Why OPV is the Correct Answer:** Oral Polio Vaccine (OPV) is a live attenuated vaccine. In an AIDS patient, the vaccine virus can undergo prolonged excretion and carries a significant risk of causing **Vaccine-Associated Paralytic Poliomyelitis (VAPP)**. Furthermore, there is a risk of the virus mutating into Vaccine-Derived Polioviruses (VDPV). Therefore, Inactivated Polio Vaccine (IPV) is the preferred alternative. **Analysis of Incorrect Options:** * **Hepatitis B Vaccine:** This is a **subunit/recombinant vaccine** (killed). It is safe in AIDS patients, although the immune response (seroconversion) may be lower than in healthy individuals. * **BCG Vaccine:** While BCG is a live vaccine and generally contraindicated in symptomatic HIV, the question asks which is "not useful." In many endemic settings, BCG is given at birth before HIV status is known. However, compared to OPV, OPV is more strictly avoided in established AIDS due to the risk of paralysis. * **Measles Vaccine:** Interestingly, WHO and IAP recommend the Measles vaccine for HIV-infected children unless they are *severely* immunocompromised, because the risk of lethal natural measles outweighs the risk of the vaccine. **High-Yield Clinical Pearls for NEET-PG:** * **General Rule:** Live vaccines (BCG, OPV, MMR, Varicella, Yellow Fever) are contraindicated in symptomatic HIV/AIDS. * **Exception:** Measles and MMR can be given if the patient is not severely immunocompromised (CD4 >15%). * **Household Contacts:** If a family member has AIDS, they should not receive OPV (to prevent fecal-oral spread of the vaccine virus); IPV should be used for the household instead.

Question 19: Prevention of disease by immunization comes under which category of disease prevention?

A. Primordial prevention
B. Primary prevention (Correct Answer)
C. Secondary prevention
D. Tertiary prevention

Explanation: **Explanation:** **1. Why Primary Prevention is Correct:** Primary prevention aims to prevent the onset of a disease by controlling causes and risk factors. It is applied during the **pre-pathogenesis phase** (before the disease process has started). Immunization is the classic example of **Specific Protection**, which is a key mode of intervention under primary prevention. By administering a vaccine, the host's immunity is bolstered against a specific pathogen, thereby preventing the disease from occurring even if exposure happens. **2. Why Other Options are Incorrect:** * **Primordial Prevention:** This focuses on preventing the *emergence* of risk factors in a population (e.g., discouraging children from starting smoking). Since immunization deals with an existing risk (the pathogen), it is not primordial. * **Secondary Prevention:** This involves **early diagnosis and prompt treatment** (e.g., screening tests like Pap smears). It aims to halt disease progression and prevent complications after the disease process has already begun. * **Tertiary Prevention:** This occurs in the late pathogenesis phase and focuses on **disability limitation and rehabilitation** (e.g., physiotherapy after a stroke) to restore function or prevent further deterioration. **3. NEET-PG High-Yield Pearls:** * **Modes of Intervention for Primary Prevention:** 1. Health Promotion (e.g., health education, environmental modification) and 2. Specific Protection (e.g., Immunization, Chemoprophylaxis, use of helmets). * **Vitamin A Prophylaxis:** This is also considered Primary Prevention (Specific Protection). * **Quaternary Prevention:** A newer concept referring to actions taken to identify patients at risk of over-medicalization and to protect them from new medical invasions.

Question 20: Which of the following statements about polio vaccination is incorrect?

A. Follow up of AFP every 30 days (Correct Answer)
B. Salk vaccine contains three types of poliovirus
C. Pulse polio doses are extra and supplemental
D. Oral polio vaccine provides intestinal immunity

Explanation: **Explanation:** The correct answer is **A (Follow up of AFP every 30 days)** because this statement is factually incorrect according to the World Health Organization (WHO) and National Polio Surveillance Project (NPSP) protocols. **1. Why Option A is incorrect (The Answer):** Acute Flaccid Paralysis (AFP) surveillance is the gold standard for detecting polio. The protocol requires a follow-up examination of the child at **60 days** (not 30 days) from the onset of paralysis to check for residual weakness. This 60-day mark is critical to differentiate between transient paralysis and the permanent paralysis characteristic of poliomyelitis. **2. Analysis of other options:** * **Option B:** The Salk vaccine (Inactivated Polio Vaccine - IPV) is a trivalent vaccine containing inactivated (killed) strains of Poliovirus Types 1, 2, and 3. * **Option C:** Pulse Polio Immunization (PPI) doses are "supplemental." They do not replace the routine primary immunization schedule but are given to children under 5 years regardless of previous vaccination status to interrupt viral transmission. * **Option D:** The Oral Polio Vaccine (OPV) is a live-attenuated vaccine that replicates in the gut, inducing local **Secretory IgA** production. This provides robust intestinal immunity, preventing the wild virus from multiplying in the gut and spreading through the community. **High-Yield NEET-PG Pearls:** * **AFP Surveillance Criteria:** 1) Detection of AFP in a child <15 years. 2) Collection of two "adequate" stool samples 24 hours apart within 14 days of onset. * **Non-Polio AFP Rate:** Should be $\geq$ 2 per 100,000 children <15 years (indicator of surveillance sensitivity). * **VAPP vs VDPV:** Vaccine-Associated Paralytic Polio (VAPP) occurs in the vaccine recipient; Vaccine-Derived Poliovirus (VDPV) is due to the virus regaining virulence through community circulation. * **Switch:** India switched from tOPV to bOPV (Types 1 & 3) in April 2016 following the global eradication of Type 2.

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

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