Vaccine and Vaccination Practice Questions

Q: The Haemophilus influenzae vaccine contains which of the following?

Polyribitol phosphate antigens. **Explanation:** The *Haemophilus influenzae* type b (Hib) vaccine is a **conjugate vaccine** targeting the primary virulence factor of the bacterium: its polysaccharide capsule. **Why Option D is Correct:** The capsule of *H. influenzae* type b is composed of **Polyribitol Phosphate (PRP)**, a polymer of ribitol, ribose, and phosphate. While PRP is highly immunogenic in adults, it is a T-independent antigen that does not elicit a strong immune response in children under two years of age. To overcome this, the PRP is **conjugated to a carrier protein** (such as Tetanus toxoid or Diphtheria CRM197). This converts the immune response to T-cell dependent, inducing high-affinity IgG antibodies and long-term mucosal immunity (memory). **Why Other Options are Incorrect:** * **Option A (LPS):** While Hib possesses lipooligosaccharide (LOS), it is an endotoxin and is not used in vaccines due to its high toxicity and poor immunogenicity. * **Option B (Live attenuated):** There is no live-attenuated vaccine for Hib. The vaccine is a subunit (capsular) vaccine. * **Option C (D-glutamate):** This refers to the polypeptide capsule of ***Bacillus anthracis***. Most bacterial capsules are polysaccharides; *B. anthracis* is a high-yield exception. **High-Yield Clinical Pearls for NEET-PG:** * **Target Population:** The Hib vaccine has significantly reduced the incidence of **epiglottitis** and **meningitis** in children. * **Schedule:** Usually given at 6, 10, and 14 weeks as part of the **Pentavalent vaccine** (DPT + HepB + Hib) in India. * **Nontypable H. influenzae:** The Hib vaccine does **not** protect against nontypable (unencapsulated) strains, which are common causes of otitis media and sinusitis.

Q: Which type of vaccine is available for Hepatitis A?

Both live and inactivated. **Explanation:** Hepatitis A virus (HAV) is a picornavirus primarily transmitted via the fecal-oral route. Unlike Hepatitis B, which uses a subunit vaccine, Hepatitis A prevention relies on both **Live Attenuated** and **Inactivated (Killed)** vaccines. 1. **Why "Both" is correct:** * **Inactivated Vaccine (e.g., Havrix, Vaqta):** This is the most widely used version globally. It is administered in two doses (0 and 6–12 months) and is highly immunogenic. * **Live Attenuated Vaccine (e.g., H2 strain):** Developed primarily in China and available in India (Biovac-A), it is administered as a single subcutaneous dose. It provides rapid immunity and is often more cost-effective. 2. **Analysis of Incorrect Options:** * **Option A & B:** These are partially correct but incomplete. Since both formulations are commercially available and used in clinical practice, "Both" is the most accurate choice. * **Option D (Subunit):** This is incorrect for Hepatitis A. Subunit vaccines (Recombinant HBsAg) are the hallmark of **Hepatitis B** vaccination, not Hepatitis A. **High-Yield Clinical Pearls for NEET-PG:** * **Post-Exposure Prophylaxis (PEP):** The Hepatitis A vaccine can be used for PEP if given within **14 days** of exposure. * **Schedule:** Inactivated vaccine is given at 1 year of age (2 doses); Live vaccine is given as a single dose after 12 months of age. * **Indication:** Travelers to endemic areas, men who have sex with men (MSM), chronic liver disease patients, and sewage workers. * **Efficacy:** Both vaccines provide long-term protection (>20 years), though the inactivated version has more extensive long-term data.

Q: All are live vaccines except:

Rabies. **Explanation:** The correct answer is **Rabies** because it is a **killed (inactivated) vaccine**. In medical microbiology, vaccines are categorized based on the state of the pathogen: live-attenuated, killed, subunit, or toxoid. **1. Why Rabies is the correct answer:** The Rabies vaccine used in humans (e.g., HDCV or PCECV) consists of the fixed virus grown in cell cultures and subsequently inactivated using chemicals like beta-propiolactone. It is never administered as a live vaccine to humans due to the 100% fatality rate of the disease. **2. Analysis of incorrect options:** * **Japanese Encephalitis (JE):** While both killed and live versions exist, the **SA-14-14-2 strain** used widely in the Universal Immunization Programme (UIP) is a **live-attenuated** vaccine. * **Poliomyelitis:** The Oral Polio Vaccine (**OPV/Sabin**) is a **live-attenuated** vaccine. (Note: The Injectable Polio Vaccine/Salk is killed, but since OPV is a classic live vaccine example, this option fits the "live" category). * **Typhoid:** The **Ty21a** oral vaccine is a **live-attenuated** formulation. (The injectable Vi antigen vaccine is a subunit vaccine). **Clinical Pearls for NEET-PG:** * **Mnemonic for Live Vaccines:** "**Rome Is My Best Place Yell**" (**R**ubella, **O**PV, **M**easles/Mumps, **E**nteric fever (Ty21a), **I**nfluenza (Intranasal), **S**mallpox, **M**ycobacterium (BCG), **B**CG, **P**olio (Sabin), **Y**ellow Fever). * **Contraindication:** Live vaccines are generally contraindicated in pregnancy and immunocompromised states (except HIV patients with CD4 >200). * **Yellow Fever:** This is the live vaccine with the longest-lasting immunity (10 years to life).

Q: Which type of vaccine is the MMR vaccine?

Live attenuated. **Explanation:** The **MMR vaccine** (Measles, Mumps, and Rubella) is a classic example of a **Live Attenuated Vaccine**. These vaccines are produced by modifying "wild" viruses or bacteria in a laboratory, usually through repeated culturing. The resulting organism remains alive and can replicate within the host to trigger a robust immune response, but it loses its pathogenicity (the ability to cause disease). **Why the other options are incorrect:** * **Killed (Inactivated):** These use organisms killed by heat or chemicals (e.g., Salk Polio, Hepatitis A). They cannot replicate, generally require multiple doses, and primarily induce humoral immunity. * **Toxoid:** These are made from inactivated toxins produced by bacteria, not the bacteria themselves (e.g., Tetanus and Diphtheria). * **Subunit:** These contain only specific fragments of the pathogen (proteins or polysaccharides) to trigger an immune response (e.g., Hepatitis B, Hib). **High-Yield Clinical Pearls for NEET-PG:** * **Route & Dose:** Administered **Subcutaneously (SC)**. The first dose is given at 9 months (as MR in India) and the second at 15–18 months. * **Contraindications:** Being a live vaccine, it is strictly **contraindicated in pregnancy** (due to theoretical risk of Congenital Rubella Syndrome) and **severely immunocompromised** individuals (e.g., low CD4 counts). * **Storage:** It is highly heat-sensitive and must be stored in the **freezer compartment** or between +2°C to +8°C. * **Reconstitution:** Must be used within **4 hours** of reconstitution; otherwise, it must be discarded due to loss of potency and risk of Staphylococcus contamination.

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

Tetanus. ### Explanation The correct answer is **D. Tetanus**. **1. Why Tetanus is the correct answer:** Vaccines are broadly classified into live-attenuated, killed (inactivated), toxoids, and subunit vaccines. **Tetanus** is a **toxoid vaccine**. It is prepared by treating the exotoxin produced by *Clostridium tetani* with formaldehyde, which renders it non-toxic while preserving its immunogenicity. It does not contain live organisms. **2. Analysis of Incorrect Options:** * **A. BCG (Bacillus Calmette-Guérin):** This is a **live-attenuated** bacterial vaccine derived from *Mycobacterium bovis*. It is the only live bacterial vaccine routinely used in the National Immunization Schedule. * **B. OPV (Oral Polio Vaccine/Sabin):** This is a **live-attenuated** viral vaccine. It induces both systemic (IgG) and local mucosal (IgA) immunity. (Note: IPV/Salk is the killed version). * **C. Measles:** This is a **live-attenuated** viral vaccine (Edmonston-Zagreb strain). It is typically administered at 9 months of age in India. **3. NEET-PG High-Yield Clinical Pearls:** * **Mnemonic for Live Vaccines:** "**B**oy **R**eally **I**s **V**ery **S**mart **Y**et **M**akes **M**any **L**ittle **T**yping **P**errors" (**B**CG, **R**otavirus, **I**ntranasal Influenza, **V**aricella, **S**abin/OPV, **Y**ellow Fever, **M**easles, **M**umps, **L**ive Typhoid/Ty21a, **P**lague). * **Contraindication:** Live vaccines are generally contraindicated in **pregnancy** and **immunocompromised** states (except HIV patients before the symptomatic stage, where BCG/Measles may be given based on CD4 counts). * **Storage:** Most live vaccines are heat-sensitive and must be stored in the **ILR (Ice-Lined Refrigerator)** at +2°C to +8°C; however, OPV is the most heat-sensitive and is stored at -20°C for long-term stability.

Q: Which is a Plasmodium falciparum vaccine strain?

RTS, S/AS01. **Explanation:** **RTS,S/AS01 (Mosquirix)** is the first malaria vaccine to receive WHO recommendation for widespread use in children. It is a recombinant protein vaccine that targets the **circumsporozoite protein (CSP)** of *Plasmodium falciparum*. * **Mechanism:** It induces antibodies and T-cells to prevent the parasite from infecting the liver (pre-erythrocytic stage). * **Composition:** The "RTS" refers to the repeat (R) and T-cell epitope (T) regions of the CSP fused to the Hepatitis B surface antigen (S). "AS01" is the chemical adjuvant system used to enhance the immune response. **Analysis of Incorrect Options:** * **RTS, RS:** This is a distractor; no such nomenclature exists for a validated malaria vaccine. * **Spf66:** Developed by Manuel Patarroyo, this was a synthetic peptide vaccine. While historically significant as one of the first candidates tested in field trials, it showed low efficacy and is not currently used. * **NYVAC-Pf7:** This was an early multi-antigen DNA vaccine candidate using a poxvirus vector. It failed to show significant protection in clinical trials. **High-Yield Clinical Pearls for NEET-PG:** * **R21/Matrix-M:** The second malaria vaccine recently recommended by the WHO (2023). It is highly effective and easier to manufacture than RTS,S. * **Target Stage:** Both RTS,S and R21 target the **pre-erythrocytic (sporozoite) stage** to prevent the blood-stage infection that causes clinical symptoms. * **Species Specificity:** These vaccines are specific to ***P. falciparum*** and do not protect against *P. vivax*. * **Dosing:** RTS,S requires a 4-dose schedule in children starting from 5 months of age.

Q: Which vaccine can cause adverse effects in persons with an allergy to eggs?

Rabies. ### Explanation The correct answer is **Rabies (Option C)**. **1. Why Rabies is the correct answer:** The potential for allergic reactions to vaccines in egg-allergic individuals depends on the substrate used for viral cultivation. Certain Rabies vaccines, specifically **Purified Chick Embryo Cell (PCEC) vaccines**, are cultured in primary cultures of chicken embryonic fibroblasts. These vaccines may contain trace amounts of egg protein (ovalbumin), which can trigger hypersensitivity reactions or anaphylaxis in sensitized individuals. While modern cell-culture vaccines are generally safe, PCEC remains the primary concern in this context. **2. Why the other options are incorrect:** * **Measles, Mumps, and Rubella (MMR):** Although these viruses are grown in chick embryo fibroblast cultures, the World Health Organization (WHO) and the Advisory Committee on Immunization Practices (ACIP) state that the amount of egg protein is negligible. Large-scale studies have shown that MMR vaccines can be safely administered to children with severe egg allergies without prior skin testing. * **Note:** In contrast, **Yellow Fever** and **Influenza** vaccines are grown in embryonated chicken eggs and contain much higher concentrations of egg protein, making them strictly contraindicated or requiring caution in egg-allergic patients. **3. High-Yield Clinical Pearls for NEET-PG:** * **Vaccines to avoid/caution in Egg Allergy:** Yellow Fever (highest risk), Influenza (Inactivated and Live), and Rabies (PCEC type). * **Safe for Egg Allergy:** MMR, MMRV, and most recombinant vaccines. * **Substrate Check:** If a question asks for the "most" contraindicated vaccine in egg allergy and Yellow Fever is an option, it is usually the primary answer. In this specific set, Rabies (PCEC) is the relevant clinical concern. * **Gelatin Allergy:** Interestingly, many reactions attributed to "egg allergy" in MMR vaccines are actually due to **gelatin** used as a stabilizer.

Q: What is the vaccine strain for yellow fever?

17D. **Explanation:** **Yellow Fever Vaccine (Strain 17D):** The correct answer is **17D**. The Yellow Fever vaccine is a **live-attenuated vaccine** derived from the wild-type Asibi strain. It was developed by Max Theiler in 1937 (for which he received a Nobel Prize). The 17D strain is highly effective, providing long-lasting immunity (often considered lifelong) after a single subcutaneous dose. It is cultured in **embryonated chicken eggs**, making a history of egg allergy a contraindication. **Analysis of Options:** * **A. 17D (Correct):** This is the globally standardized strain used for all yellow fever vaccinations. It exists in two sub-strains: 17D-204 and 17DD, both of which are clinically equivalent. * **B, C, and D (5D, 4D, 2D):** These are distractors. There are no recognized human vaccines for yellow fever or other major viral pathogens using these specific alphanumeric designations. **High-Yield Clinical Pearls for NEET-PG:** * **Type of Vaccine:** Live-attenuated (cannot be given to immunocompromised individuals or infants <6 months). * **Dosage:** 0.5 ml administered subcutaneously. * **Validity:** International Health Regulations (IHR) now state that a single dose provides lifelong protection; the certificate becomes valid **10 days** after vaccination and lasts for life. * **Contraindications:** Egg hypersensitivity, thymus disorders, and symptomatic HIV/AIDS. * **Council of India Requirement:** Yellow Fever vaccination is mandatory for travelers arriving from or transiting through endemic zones (Africa and South America) to India. * **Vector:** Primarily transmitted by the *Aedes aegypti* mosquito.

Question 1

The Haemophilus influenzae vaccine contains which of the following?

Accepted Answer

Polyribitol phosphate antigens

Answer

Lipopolysaccharide (LPS)

Answer

Live attenuated H. influenzae

Answer

Polypeptide antigens containing D-glutamate

Question 2

Which type of vaccine is available for Hepatitis A?

Accepted Answer

Both live and inactivated

Answer

Live attenuated

Answer

Killed (Inactivated)

Answer

Subunit vaccine

Question 3

All are live vaccines except:

Accepted Answer

Rabies

Answer

Japanese encephalitis

Answer

Poliomyelitis

Answer

Typhoid

Question 4

Which type of vaccine is the MMR vaccine?

Accepted Answer

Live attenuated

Answer

Killed

Answer

Toxoid

Answer

Subunit

Question 5

Which of the following is not a live vaccine?

Accepted Answer

Tetanus

Answer

BCG

Answer

OPV

Answer

Measles

Question 6

Which is a Plasmodium falciparum vaccine strain?

Accepted Answer

RTS, S/AS01

Answer

RTS, RS

Answer

Spfl6

Answer

NYVAC-PF01

Question 7

Which vaccine can cause adverse effects in persons with an allergy to eggs?

Accepted Answer

Rabies

Answer

Measles

Answer

Rubella

Answer

Mumps

Question 8

What is the role of an adjuvant in a DPT vaccine?

Accepted Answer

Increase antigenicity

Answer

Decrease hypersensitivity

Answer

Decrease absorption of vaccine

Answer

Increase the shelf life of a vaccine

Question 9

Which of the following statements regarding live vaccines is false?

Accepted Answer

Two live vaccines can be administered simultaneously.

Answer

Booster doses are not required when live vaccines are administered.

Answer

A single dose gives lifelong immunity.

Answer

Live vaccines contain both major and minor antigens.

Question 10

What is the vaccine strain for yellow fever?

Accepted Answer

17D

Answer

5D

Answer

4D

Answer

2D

Vaccine and Vaccination — MCQs

Vaccine and Vaccination — MCQs

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