Vaccine and Vaccination Practice Questions

Q: Which of the following is NOT a live vaccine?

Salk vaccine. The correct answer is **B. Salk vaccine**. ### **Explanation** The fundamental concept here is the classification of vaccines into **Live Attenuated** and **Killed (Inactivated)** types. * **Salk vaccine (IPV - Inactivated Poliovirus Vaccine):** This is a killed vaccine, produced by inactivating the virus using formaldehyde. Because the pathogen is dead, it cannot replicate in the host but still triggers an immune response. * **Sabin vaccine (OPV - Oral Polio Vaccine):** In contrast, Sabin is a live attenuated vaccine. A common NEET-PG mnemonic to remember this is: *"Salk = K for Killed; Sabin = Live."* ### **Analysis of Incorrect Options** * **A. BCG (Bacillus Calmette-Guérin):** A live attenuated bacterial vaccine derived from *Mycobacterium bovis*. It is the only live bacterial vaccine routinely used in the national schedule. * **C & D. Measles and Mumps:** Both are live attenuated viral vaccines. They are typically administered as part of the MMR (Measles, Mumps, Rubella) or MR combination. ### **High-Yield Clinical Pearls for NEET-PG** * **Live Vaccines Mnemonic:** *"**B**oy **R**omeo **G**ive **M**y **L**ove **S**picy **V**ictory **T**onight"* (BCG, Rotavirus, OPV, MMR, L-Ty21a, Smallpox/Sabin, Varicella, Yellow Fever). * **Contraindications:** Live vaccines are generally contraindicated in **pregnancy** and **immunocompromised** individuals (except HIV patients with CD4 counts >200). * **Killed Vaccines:** Examples include Salk (IPV), Hepatitis A, Rabies, and the Whole-cell Pertussis component. * **Storage:** Most live vaccines are heat-sensitive and must be stored in the "cold chain" (usually +2°C to +8°C).

Q: A person who has received the full course of vaccine against Hepatitis B Virus (HBV) wants to know the response to the vaccine. Which serological marker should be tested to assess vaccine response?

Antibody to Hepatitis B surface antigen (Anti-HBsAg). **Explanation:** The Hepatitis B vaccine is a **subunit vaccine** containing recombinant **HBsAg** (Hepatitis B surface antigen). When administered, the body’s immune system recognizes this surface protein and produces specific neutralizing antibodies against it. Therefore, the presence of **Anti-HBsAg** (Antibody to HBsAg) is the definitive marker of immunity following vaccination. **Analysis of Options:** * **Anti-HBsAg (Correct):** This is the only marker that appears after successful vaccination. A titer of **≥10 mIU/mL** is generally considered protective. * **HBsAg (Incorrect):** This is a marker of active infection (either acute or chronic). It represents the presence of the virus itself, not the immune response to the vaccine. * **IgM anti-HBc (Incorrect):** This antibody is produced against the "core" antigen of the virus. Since the vaccine only contains the "surface" antigen and not the core, this marker will be **negative** in a vaccinated person. It is a hallmark of **acute/recent natural infection**. * **HBeAg (Incorrect):** This is a marker of active viral replication and high infectivity. It is never found as a result of vaccination. **NEET-PG High-Yield Pearls:** 1. **Isolated Anti-HBs (+):** Indicates immunity due to **vaccination**. 2. **Anti-HBs (+) AND Anti-HBc (+):** Indicates immunity due to **natural infection** (recovery). 3. **Window Period:** The period where HBsAg disappears but Anti-HBs has not yet appeared. The only diagnostic marker here is **IgM anti-HBc**. 4. **Non-responders:** Individuals who do not develop a titer of ≥10 mIU/mL after a full 3-dose series.

Q: Which of the following best describes the Yellow fever vaccine?

Live attenuated vaccine. The **Yellow Fever vaccine (17D strain)** is a classic example of a **live attenuated vaccine**. It is prepared by serial passage of the virus in chick embryos, which reduces its virulence while maintaining its ability to induce a robust, long-lasting immune response. ### Explanation of Options: * **Option B (Correct):** The 17D strain is a live attenuated virus. It provides exceptionally high efficacy (nearly 100%) and is known for its longevity; a single dose is now considered by the WHO to provide life-long immunity for most travelers. * **Option A (Incorrect):** Killed (inactivated) vaccines (e.g., Salk Polio, Hepatitis A) use heat or chemicals to destroy the pathogen's ability to replicate. The Yellow Fever vaccine must replicate in the host to be effective. * **Option C (Incorrect):** Toxoids are inactivated toxins produced by bacteria (e.g., Tetanus, Diphtheria). Yellow Fever is a viral disease, not a toxin-mediated bacterial one. * **Option D (Incorrect):** Subcellular (subunit) vaccines use only specific fragments of the pathogen (e.g., Hepatitis B surface antigen). The 17D vaccine uses the whole attenuated virus. ### High-Yield Clinical Pearls for NEET-PG: * **Route & Dose:** 0.5 ml, administered **Subcutaneously**. * **Validity:** The International Certificate of Vaccination becomes valid **10 days** after vaccination and lasts for **life**. * **Contraindications:** Infants <6 months, pregnant women (unless in high-risk outbreaks), symptomatic HIV/AIDS, and individuals with **egg hypersensitivity** (as it is grown in chick embryos). * **Cold Chain:** It is highly heat-sensitive and must be stored between **+2°C to +8°C**. * **Strains:** Derived from the wild Asibi strain.

Q: Vaccination for which of the following hepatic diseases is with viral surface antigen and usually provides immunity?

Hepatitis B. **Explanation:** The correct answer is **Hepatitis B**. The Hepatitis B vaccine is a **subunit recombinant vaccine** produced using recombinant DNA technology in yeast (*Saccharomyces cerevisiae*). It specifically utilizes the **Hepatitis B surface Antigen (HBsAg)**. When injected, the body produces **Anti-HBs antibodies**, which are neutralizing and provide long-term immunity. A titer of >10 mIU/mL is considered protective. **Analysis of Options:** * **Hepatitis A:** The vaccine is typically an **inactivated (killed) whole-virus vaccine** (e.g., Havrix). While it provides excellent immunity, it uses the entire virion rather than just a surface antigen. * **Hepatitis C:** There is currently **no vaccine** available for Hepatitis C due to the high antigenic variation and lack of a proofreading mechanism in its RNA polymerase. * **Hepatitis D:** There is no specific vaccine for HDV. However, because HDV is a defective virus that requires HBsAg for its coat, **vaccination against Hepatitis B** automatically protects an individual from HDV infection. **High-Yield Clinical Pearls for NEET-PG:** * **HBsAg** is the first serological marker to appear in acute infection and the key component of the vaccine. * **Anti-HBs** is the only marker present in a successfully vaccinated individual (Anti-HBc will be negative). * The HBV vaccine is given at **0, 1, and 6 months**. * **Non-responders:** Individuals who fail to develop a protective antibody titer after two complete series of vaccinations.

Q: All of the following are cellular vaccines except:

Tetanus toxoid. ### Explanation The classification of vaccines is based on the nature of the antigen used to stimulate the immune system. Vaccines can be broadly categorized into **Cellular (Whole-cell)** vaccines and **Acellular (Subunit/Toxin-based)** vaccines. **Why Tetanus Toxoid is the correct answer:** Tetanus toxoid is **not a cellular vaccine**; it is a **toxoid**. It is prepared by detoxifying the exotoxin produced by *Clostridium tetani* using formaldehyde. The resulting product is an immunogenic protein (antigen) but does not contain the bacterial cell itself. Therefore, it is classified as an acellular, toxin-based vaccine. **Analysis of Incorrect Options:** * **BCG (Bacillus Calmette–Guérin):** This is a **Live Attenuated Bacterial** vaccine containing live, weakened cells of *Mycobacterium bovis*. Since it contains the whole bacterial cell, it is a cellular vaccine. * **Measles Vaccine:** This is a **Live Attenuated Viral** vaccine. It contains the whole (though weakened) virus particle, making it a cellular/whole-organism vaccine. * **DPT (Diphtheria, Pertussis, Tetanus):** While Diphtheria and Tetanus components are toxoids, the traditional **Pertussis** component (wP) in the DPT combination is a **killed whole-cell** vaccine. Thus, the DPT vaccine contains cellular components. **High-Yield Clinical Pearls for NEET-PG:** * **Toxoids:** Only two major toxoids are used in the routine immunization schedule: **Tetanus** and **Diphtheria**. * **Acellular Pertussis (aP):** Modern DTaP vaccines use purified components (like pertussis toxoid) instead of the whole cell to reduce febrile seizures and local reactions. * **Freeze Sensitivity:** Tetanus toxoid is highly sensitive to freezing (must be stored at +2°C to +8°C). If frozen, it loses potency (confirmed by the **Shake Test**). * **Route:** Tetanus toxoid is always administered **Intramuscularly (IM)**.

Q: Which of the following is a killed vaccine?

Japanese encephalitis. **Explanation:** The correct answer is **Japanese Encephalitis (JE)**. In the context of the Indian National Immunization Schedule and common medical entrance exams, the **K-JE (Jenvac)** is a potent, inactivated (killed) vaccine derived from the Kolar strain. While a live attenuated vaccine (SA-14-14-2) also exists, JE is frequently tested as a killed vaccine in competitive exams. **Analysis of Options:** * **Japanese Encephalitis (Option D):** The inactivated JE vaccine is produced by growing the virus in Vero cells and then inactivating it with formaldehyde. It is highly effective and used widely in endemic regions. * **Hepatitis B (Option A):** This is a **Recombinant/Subunit vaccine**, not a killed whole-virus vaccine. It is produced using recombinant DNA technology in yeast cells (*Saccharomyces cerevisiae*) to express the HBsAg surface antigen. * **Measles (Option B):** This is a **Live Attenuated vaccine**. It is typically administered as part of the MMR or MR vaccine. * **Yellow Fever (Option C):** This is a classic **Live Attenuated vaccine** (17D strain). It is famous for being one of the most effective vaccines, providing lifelong immunity. **NEET-PG High-Yield Pearls:** * **Mnemonic for Killed Vaccines:** "**KIL**P" – **K**illed **I**PV (Salk), **L**ethal **P**lague, **P**ertussis, **R**abies, **I**nfluenza, **H**epatitis A, and **J**apanese Encephalitis (Kolar strain). * **Live Vaccines Mnemonic:** "**BOY** **R**eally **L**oves **C**rime **M**ovies" – **B**CG, **O**PV (Sabin), **Y**ellow Fever, **R**otavirus, **L**ive Typhoid (Ty21a), **C**hickenpox, **M**easles/Mumps/Rubella. * **Note:** Always check if the question specifies the strain; for JE, the **SA-14-14-2** is Live, while **Jenvac/Kolar** is Killed.

Q: The influenza vaccine contains all strains of influenza virus except which one?

H2N1. **Explanation:** The influenza vaccine is designed to protect against the strains currently circulating in the human population that pose the greatest public health threat. **Why H2N1 is the Correct Answer:** The **H2N1** subtype is not a common human pathogen and is not included in the seasonal influenza vaccine. While H2N2 caused the "Asian Flu" pandemic in 1957, it has not circulated in humans since 1968. H2N1, specifically, is not a standard component of any WHO-recommended trivalent or quadrivalent vaccine formulation. **Analysis of Incorrect Options:** * **H1N1 (Option A):** This is a subtype of Influenza A. Since the 2009 pandemic, the H1N1 strain (specifically A/pdm09) has been a core component of the seasonal vaccine. * **H3N2 (Option B):** This is another subtype of Influenza A that causes significant morbidity and mortality, especially in the elderly. It is a standard component of both trivalent and quadrivalent vaccines. * **Influenza B (Option D):** Influenza B viruses are included in all seasonal vaccines. Trivalent vaccines contain one lineage (Victoria or Yamagata), while quadrivalent vaccines contain both. **High-Yield NEET-PG Pearls:** 1. **Composition:** The **Quadrivalent vaccine** (most common today) contains two Influenza A strains (H1N1, H3N2) and two Influenza B lineages (Victoria, Yamagata). 2. **Antigenic Shift vs. Drift:** *Drift* (point mutations) causes seasonal epidemics; *Shift* (genetic reassortment) causes pandemics. 3. **Timing:** Because the virus undergoes frequent antigenic drift, the WHO reviews and updates the vaccine composition twice a year (Northern and Southern Hemisphere recommendations). 4. **Contraindication:** Severe egg allergy is a traditional precaution (though cell-based vaccines now exist).

Q: Which of the following strains of wild poliovirus forms the salk type 1 component of inactivated polio vaccine?

Mahoney. The **Inactivated Polio Vaccine (IPV)**, also known as the **Salk vaccine**, is composed of wild-type poliovirus strains that have been inactivated (killed) using formalin. It provides systemic immunity (IgG) but lacks the local mucosal immunity (IgA) provided by the oral vaccine. ### Why Mahoney is Correct The Salk vaccine is trivalent, containing three specific reference strains of wild poliovirus: * **Type 1: Mahoney strain** * **Type 2: MEF-1** (Middle East Forces 1) strain * **Type 3: Saukett** strain The **Mahoney strain** was selected for Type 1 because of its high antigenicity and ability to induce a robust immune response, despite being highly neurovirulent in its live state. ### Explanation of Incorrect Options * **A. MEF-1:** This is the reference strain used for **Type 2** poliovirus in the Salk vaccine. * **C. Salkett:** This is a distractor name; the actual strain for **Type 3** is **Saukett** (named after the patient from whom it was isolated). * **D. Leningrad-3:** This strain is associated with the **Live Attenuated Mumps vaccine**, not the polio vaccine. ### High-Yield Clinical Pearls for NEET-PG * **Sabin vs. Salk:** Sabin (OPV) uses live attenuated strains (**P1: LSc 2ab, P2: P712, P3: Leon 12a1b**). * **VDPV:** Vaccine-Derived Poliovirus is most commonly associated with the **Type 2** strain of OPV, which is why the world switched from trivalent OPV (tOPV) to bivalent OPV (bOPV) and introduced IPV into routine schedules. * **Route:** IPV is typically given Intramuscularly (IM), but India uses **Fractional IPV (fIPV)** given Intradermally (ID) at 6, 14 weeks, and 9 months to stretch vaccine supply.

Q: A vaccine is available for one of the most common causes of infantile gastroenteritis. This vaccine has recently been recalled. Which virus is this?

Rotavirus. **Explanation:** **Rotavirus** is the most common cause of severe, dehydrating infantile gastroenteritis worldwide. The question refers to the historical and clinical context of the **Rotashield** vaccine (the first-generation live-attenuated rhesus-based vaccine), which was recalled in 1999 due to a statistically significant association with **intussusception**. While newer vaccines like Rotarix and RotaTeq are now part of the Universal Immunization Programme (UIP) and are safe, the "recall" association remains a classic high-yield fact in medical exams. **Analysis of Incorrect Options:** * **A. Cytomegalovirus (CMV):** While a major cause of congenital infections, there is currently no licensed vaccine available for CMV. * **C. Varicella-zoster virus:** The vaccine (live-attenuated Oka strain) is widely used to prevent chickenpox and shingles and has not been recalled for gastroenteritis-related issues. * **D. Adenovirus:** While Adenovirus types 40 and 41 cause gastroenteritis, the available vaccine (oral, live) is only used for military recruits to prevent respiratory outbreaks (types 4 and 7), not for infantile diarrhea. **High-Yield Clinical Pearls for NEET-PG:** * **Morphology:** Rotavirus belongs to the *Reoviridae* family; it is a dsRNA virus with a wheel-like appearance (*Rota* = wheel) under electron microscopy. * **Pathogenesis:** It produces an enterotoxin called **NSP4**, which induces secretory diarrhea by increasing intracellular calcium. * **Diagnosis:** The gold standard for rapid detection in stool is **ELISA** (detecting VP6 antigen) or Latex Agglutination. * **Current Vaccines:** Rotavac (India) and Rotasiil are current vaccines used in India's UIP, administered orally at 6, 10, and 14 weeks.

Q: The quadrivalent vaccine available for HPV is protective against which serotypes?

HPV 6, 11, 16, 18. **Explanation:** The Human Papillomavirus (HPV) vaccine is a high-yield topic for NEET-PG, focusing on the prevention of cervical cancer and genital warts. The **Quadrivalent vaccine (Gardasil)** is designed to target the four most clinically significant serotypes: * **HPV 6 and 11:** These are "low-risk" types responsible for approximately 90% of **anogenital warts** (Condyloma acuminata) and recurrent respiratory papillomatosis. * **HPV 16 and 18:** These are "high-risk" oncogenic types responsible for approximately 70% of **cervical cancers**, as well as most anal, vulvar, and vaginal cancers. **Analysis of Options:** * **Option D (Correct):** Correctly identifies the four serotypes (6, 11, 16, 18) covered by the quadrivalent vaccine. * **Options A, B, and C:** These are incorrect because they include serotypes like 31, 32, 33, and 35. While types 31 and 33 are high-risk, they are only covered by the **Nonavalent vaccine (Gardasil 9)**, not the quadrivalent version. **High-Yield Clinical Pearls for NEET-PG:** 1. **Types of Vaccines:** * **Bivalent (Cervarix):** 16, 18 (Prevents cancer). * **Quadrivalent (Gardasil):** 6, 11, 16, 18 (Prevents cancer + warts). * **Nonavalent (Gardasil 9):** 6, 11, 16, 18, 31, 33, 45, 52, 58. 2. **Vaccine Composition:** These are **L1 VLP (Virus-Like Particle)** vaccines; they do not contain viral DNA and are non-infectious. 3. **Target Age:** Ideally administered before the onset of sexual activity (9–14 years). 4. **Oncogenesis:** HPV-16 is the most common type associated with Squamous Cell Carcinoma, while HPV-18 is strongly linked to Adenocarcinoma of the cervix.

Question 1

Which of the following is NOT a live vaccine?

Accepted Answer

Salk vaccine

Answer

BCG

Answer

Measles

Answer

Mumps

Question 2

A person who has received the full course of vaccine against Hepatitis B Virus (HBV) wants to know the response to the vaccine. Which serological marker should be tested to assess vaccine response?

Accepted Answer

Antibody to Hepatitis B surface antigen (Anti-HBsAg)

Answer

Hepatitis B surface antigen (HBsAg)

Answer

IgM antibody to Hepatitis B core antigen (IgM anti-HBc)

Answer

Hepatitis B e antigen (HBeAg)

Question 3

Which of the following best describes the Yellow fever vaccine?

Accepted Answer

Live attenuated vaccine

Answer

Killed vaccine

Answer

Toxoid

Answer

Subcellular vaccine

Question 4

Vaccination for which of the following hepatic diseases is with viral surface antigen and usually provides immunity?

Accepted Answer

Hepatitis B

Answer

Hepatitis A

Answer

Hepatitis C

Answer

Hepatitis D

Question 5

All of the following are cellular vaccines except:

Accepted Answer

Tetanus toxoid

Answer

BCG

Answer

Measles vaccine

Answer

DPT

Question 6

Which of the following is a killed vaccine?

Accepted Answer

Japanese encephalitis

Answer

Hepatitis B

Answer

Measles

Answer

Yellow fever

Question 7

The influenza vaccine contains all strains of influenza virus except which one?

Accepted Answer

H2N1

Answer

H1N1

Answer

H3N2

Answer

Influenza B

Question 8

Which of the following strains of wild poliovirus forms the salk type 1 component of inactivated polio vaccine?

Accepted Answer

Mahoney

Answer

MEF-1

Answer

Salkett

Answer

Leningrad-3

Question 9

A vaccine is available for one of the most common causes of infantile gastroenteritis. This vaccine has recently been recalled. Which virus is this?

Accepted Answer

Rotavirus

Answer

Cytomegalovirus

Answer

Varicella-zoster virus

Answer

Adenovirus

Question 10

The quadrivalent vaccine available for HPV is protective against which serotypes?

Accepted Answer

HPV 6, 11, 16, 18

Answer

HPV 6, 11, 31, 32

Answer

HPV 16, 18, 31, 35

Answer

HPV 11, 16, 30, 33

Vaccine and Vaccination — MCQs

Vaccine and Vaccination — MCQs

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