Vaccine and Vaccination Practice Questions

Q: What is the role of Mg++ in vaccines?

Stabilizer. **Explanation:** **1. Why Magnesium (Mg++) is the Correct Answer:** Magnesium ions ($Mg^{2+}$), typically in the form of Magnesium Chloride ($MgCl_2$), act as **thermal stabilizers**. Their primary role is to maintain the structural integrity and potency of the vaccine antigen (especially live-attenuated viruses) when exposed to heat. $Mg^{2+}$ prevents the thermal degradation of viral proteins and nucleic acids, ensuring the vaccine remains effective even if the cold chain is briefly compromised. * **Classic Example:** The Oral Polio Vaccine (OPV) uses $MgCl_2$ as a stabilizer to protect the live virus from heat-induced inactivation. **2. Why Other Options are Incorrect:** * **Preservative (e.g., Thiomersal, Phenol):** These are added to multi-dose vials to prevent the growth of bacteria or fungi. They do not stabilize the antigen itself. * **Adjuvant (e.g., Alum/Aluminum salts):** These are substances added to enhance or "boost" the body's immune response to the vaccine antigen. $Mg^{2+}$ does not have immunomodulatory properties. * **Vehicle (e.g., Normal Saline, Sterile Water):** This is the liquid medium (diluent) used to dissolve or suspend the vaccine components for administration. **3. High-Yield Clinical Pearls for NEET-PG:** * **OPV Stability:** $MgCl_2$ is the most high-yield stabilizer associated with OPV. * **Other Stabilizers:** Sugars (sucrose, lactose), amino acids (glycine), and proteins (gelatin, albumin) are also used as stabilizers. * **Adjuvant Fact:** Aluminum hydroxide/phosphate (Alum) is the most common adjuvant; it is **never** used in live vaccines (like BCG or OPV) as it can interfere with viral replication. * **Thiomersal:** A mercury-containing preservative used in DPT and Hepatitis B vaccines, but absent in single-dose live vaccines.

Q: Which of the following is/are subunit vaccines?

Typhoid Vi. **Explanation:** **Subunit vaccines** are a type of fractional vaccine that contains only specific antigenic parts of the pathogen (such as proteins, polysaccharides, or capsids) rather than the whole organism. This reduces the risk of adverse reactions while still inducing protective immunity. 1. **Why Typhoid Vi is correct:** The **Typhoid Vi** vaccine is a **capsular polysaccharide subunit vaccine**. It is derived from the purified Vi capsular antigen of *Salmonella typhi*. Unlike the live-attenuated oral vaccine (Ty21a), the Vi injectable vaccine is a classic example of a subunit preparation. 2. **Analysis of other options:** * **Haemophilus influenzae type b (Hib):** While Hib is technically a subunit vaccine, it is more specifically classified as a **Conjugate vaccine**. In these, the polysaccharide is linked to a carrier protein to enhance immunogenicity in infants. In NEET-PG, if "Conjugate" and "Subunit" are both possibilities, Hib is categorized under Conjugates. * **Hepatitis B vaccine:** This is a **Recombinant DNA vaccine**. It uses only the HBsAg surface protein produced in yeast cells. While it is a subunit of the virus, it is specifically tested as a "Recombinant" vaccine in exams. * **Diphtheria vaccine:** This is a **Toxoid**. It is made from inactivated exotoxins, not structural subunits of the bacteria. **High-Yield Clinical Pearls for NEET-PG:** * **Subunit Categories:** * **Polysaccharide:** Typhoid Vi, Meningococcal, Pneumococcal (PPV-23). * **Recombinant:** Hepatitis B, HPV (Human Papillomavirus). * **Conjugate:** Hib, PCV-13 (Pneumococcal), MCV-4 (Meningococcal). * **Key Distinction:** Subunit vaccines are generally **non-living**, meaning they cannot cause the disease and are safe for immunocompromised patients, but they often require **adjuvants** and multiple booster doses to maintain immunity.

Q: Which statement is NOT true regarding the measles vaccine?

It is grown in egg culture.. The measles vaccine is a live-attenuated vaccine (Edmonston-Zagreb strain) that is a staple of the Universal Immunization Programme (UIP). **Explanation of the Correct Answer:** * **Option A (Incorrect Statement):** The measles vaccine is **not** grown in egg culture. It is prepared using **Chick Embryo Fibroblast (CEF) cell cultures**. While it uses cells derived from embryos, it is distinct from "egg culture" (like the Influenza or Yellow Fever vaccines). This is a high-yield distinction for exams. **Analysis of Other Options:** * **Option B (True):** The vaccine is supplied in a **freeze-dried (lyophilized)** form to maintain stability. It must be stored between +2°C to +8°C and protected from light. * **Option C (True):** Once reconstituted with the provided diluent (Sterile Water for Injection), the vaccine is highly thermolabile and prone to bacterial contamination. It must be used within **4 to 6 hours** (though many guidelines emphasize "as soon as possible," and the 1-hour mark is often used as a safety threshold in specific clinical contexts; however, in the context of this MCQ, Option A is the definitive false statement). * **Option D (True):** In India, the first dose is administered at **9 completed months**. Administering it earlier is avoided because maternal antibodies can neutralize the vaccine virus, rendering it ineffective. **NEET-PG High-Yield Pearls:** * **Strain:** Edmonston-Zagreb (most common in India). * **Route:** Subcutaneous (0.5 ml). * **Side Effect:** Toxic Shock Syndrome (TSS) can occur if the reconstituted vaccine is kept for too long due to *Staphylococcus aureus* contamination. * **Contraindication:** Severe immunosuppression (e.g., advanced HIV), but **not** egg allergy (since it is grown in fibroblast culture, not egg protein).

Q: What type of vaccine is the MMR vaccine?

Killed. **Explanation:** The **MMR vaccine** (Measles, Mumps, and Rubella) is a classic example of a **Live Attenuated Vaccine**. It consists of live viruses that have been weakened (attenuated) in a laboratory so they can replicate and induce a robust immune response without causing the actual disease in healthy individuals. *Note: There appears to be a discrepancy in the provided key; medically and academically, MMR is universally classified as a Live Attenuated vaccine.* **Analysis of Options:** * **Live Attenuated (Correct Concept):** These vaccines trigger both humoral (B-cell) and cell-mediated (T-cell) immunity, often providing lifelong protection with one or two doses. Examples include MMR, Varicella, BCG, and Oral Polio (Sabin). * **Killed (Inactivated):** These contain microorganisms killed by heat or chemicals (e.g., Formalin). They are safer for immunocompromised patients but usually require booster doses (e.g., IPV, Hepatitis A, Rabies). * **Toxoid:** These are made from inactivated bacterial toxins (e.g., Tetanus and Diphtheria). * **Subunit:** These contain only specific fragments of the pathogen (e.g., Hepatitis B surface antigen, HPV). **High-Yield Clinical Pearls for NEET-PG:** * **Route:** MMR is administered **Subcutaneously (SC)**. * **Schedule:** 1st dose at 9–12 months (as MR in India's NIS) and 2nd dose at 16–24 months. * **Contraindications:** Pregnancy (due to theoretical risk of Congenital Rubella Syndrome) and severely immunocompromised states (HIV with CD4 <200). * **Storage:** It is highly heat-sensitive and must be stored at **2°C to 8°C**, protected from light.

Q: The acellular pertussis vaccine contains which of the following components?

Filamentous hemagglutinin, pertussis toxin, fimbriae. **Explanation:** The **Acellular Pertussis (aP) vaccine** was developed to reduce the high rate of adverse reactions (like fever and febrile seizures) associated with the Whole-cell Pertussis (wP) vaccine. While the wP vaccine contains the entire killed *Bordetella pertussis* organism, the aP vaccine contains only specific, purified immunogenic proteins. **Why Option D is Correct:** The acellular vaccine typically consists of 1 to 5 highly purified antigens. The most common components include: 1. **Pertussis Toxin (PT):** Inactivated toxin that induces neutralizing antibodies. 2. **Filamentous Hemagglutinin (FHA):** A protein required for adhesion to ciliated respiratory epithelial cells. 3. **Fimbriae (Types 2 and 3):** Surface proteins involved in colonization. 4. **Pertactin (PRN):** An outer membrane protein that aids in attachment. **Analysis of Incorrect Options:** * **Options A & B:** These are incorrect because they include **Endotoxin (Lipopolysaccharide/LPS)**. LPS is a component of the Gram-negative cell wall and is the primary cause of the systemic toxicity and reactogenicity (fever, pain) seen in the whole-cell vaccine. It is strictly excluded from acellular preparations. * **Option C:** While it contains valid components, Option D is a more comprehensive representation of the standard multi-component aP vaccines used in DTaP formulations. **High-Yield Clinical Pearls for NEET-PG:** * **DTaP vs. Tdap:** DTaP (higher antigen dose) is used for primary immunization in children <7 years. Tdap (reduced antigen dose) is used as a booster for adolescents and adults. * **Safety:** aP vaccines have a significantly lower risk of **encephalopathy** and **hypotonic-hyporesponsive episodes (HHE)** compared to wP vaccines. * **Efficacy:** While safer, aP vaccines may have a shorter duration of immunity compared to the whole-cell version, leading to the need for regular boosters.

Q: What is the strain used for the production of the Measles vaccine?

Edmonston Zagreb strain. **Explanation:** The **Edmonston-Zagreb (EZ) strain** is the most widely used strain for the production of the Measles vaccine globally, including in India (produced by the Serum Institute). It is a live-attenuated vaccine derived from the original Edmonston strain but further adapted in human diploid cells (WI-38). This strain is preferred because it is highly immunogenic and can induce seroconversion even in the presence of low levels of maternal antibodies, making it suitable for administration in infants. **Analysis of Incorrect Options:** * **A. Jeryl Lynn strain:** This is the live-attenuated strain used for the **Mumps** vaccine (part of the MMR/MMRV combination). * **B. 17-D strain:** This is the specific attenuated strain used for the **Yellow Fever** vaccine. It is grown in chick embryos. * **C. Ankara strain:** Specifically the "Modified Vaccinia Ankara" (MVA) strain, it was used in the development of **Smallpox** vaccines and currently serves as a vector for various recombinant vaccines (e.g., Ebola). **High-Yield Clinical Pearls for NEET-PG:** * **Measles Vaccine Timing:** Under the National Immunization Schedule (NIS) in India, the 1st dose is given at **9 completed months** (subcutaneous) and the 2nd dose at **16–24 months**. * **Reconstitution:** The vaccine is lyophilized (freeze-dried) and must be reconstituted with **Sterile Water**. Once reconstituted, it must be used within **4 hours**; otherwise, it must be discarded due to the risk of *Staphylococcus aureus* contamination and Toxic Shock Syndrome. * **Contraindication:** Being a live vaccine, it is contraindicated in pregnancy and severely immunocompromised individuals.

Q: The SA 14-14-2 strain is used in the preparation of which vaccine?

JE vaccine. **Explanation:** The **SA 14-14-2 strain** is a live-attenuated virus strain used globally for the production of the **Japanese Encephalitis (JE) vaccine**. Originally developed in China by passing the wild-type SA 14 strain through primary hamster kidney cells, it is now the most widely used JE vaccine in endemic regions, including India (under the Universal Immunization Programme). **Analysis of Options:** * **A. JE vaccine (Correct):** The SA 14-14-2 is a live-attenuated vaccine. Other JE vaccines include the inactivated mouse brain-derived (Nakayama strain) and the cell culture-derived inactivated vaccine (JENVAC using the Indian Kolar strain). * **B. Typhoid vaccine:** Common strains used for typhoid vaccines include **Ty21a** (oral live-attenuated) and the **Vi capsular polysaccharide** (injectable). * **C. Influenza vaccine:** These vaccines typically use strains recommended annually by the WHO (e.g., H1N1, H3N2, and Type B strains). Live-attenuated versions (LAIV) use cold-adapted, temperature-sensitive master donor viruses. * **D. HPV vaccine:** These are subunit vaccines made of **L1 virus-like particles (VLPs)**. Common brands include Gardasil (quadrivalent/nonavalent) and Cervarix (bivalent). **High-Yield Clinical Pearls for NEET-PG:** * **Vector:** JE is transmitted by the *Culex tritaeniorhynchus* mosquito (breeds in rice fields). * **Reservoir:** Pigs (amplifier hosts) and water birds (Ardeid birds). * **Diagnosis:** IgM Capture ELISA (MAC-ELISA) of CSF or serum is the gold standard. * **Vaccination Schedule:** Under India’s UIP, two doses are given at 9 months and 16–24 months of age.

Q: Rabies vaccine is prepared from which strain of virus?

Fixed Virus. **Explanation:** The correct answer is **Fixed Virus**. In virology, the Rabies virus exists in two forms based on its laboratory modification: **Street virus** and **Fixed virus**. 1. **Why Fixed Virus is correct:** The "Fixed" virus is a street virus that has been serially passaged (usually 40–50 times) through the brains of rabbits. This process "fixes" the incubation period to a short, predictable duration (4–6 days). Crucially, while it remains immunogenic, it loses its ability to replicate in extraneural tissue and does not form Negri bodies. Because of its stable characteristics and high antigenicity, it is used for the preparation of both **Anti-Rabies Vaccines (ARV)** and diagnostic antigens. 2. **Why other options are incorrect:** * **Street Virus (A & C):** This is the virus as it exists in nature (wild virus) isolated from infected animals or humans. It has a long and highly variable incubation period (20–60 days), produces **Negri bodies**, and is highly pathogenic. It cannot be used for vaccines because its behavior is unpredictable and too virulent. * **All of the above (D):** Only the modified "Fixed" strain is safe and standardized for vaccine production. **High-Yield Clinical Pearls for NEET-PG:** * **Negri Bodies:** Pathognomonic for Rabies; found in the cytoplasm of neurons (Hippocampus/Purkinje cells). They are present in **Street virus** infections but **absent** in Fixed virus infections. * **Vaccine Strains:** Common fixed strains used include the **Pitman-Moore (PM) strain**, Pasteur strain, and Flury strain. * **Neural vs. Non-neural:** Modern vaccines (like HDCV or PCEV) are inactivated fixed viruses grown in cell cultures, replacing the older, side-effect-prone neural (Semple) vaccines.

Question 1

What is the role of Mg++ in vaccines?

Accepted Answer

Stabilizer

Answer

Preservative

Answer

Adjuvant

Answer

Vehicle

Question 2

Which of the following is/are subunit vaccines?

Accepted Answer

Typhoid Vi

Answer

Haemophilus influenzae type b (Hib) vaccine

Answer

Hepatitis B vaccine

Answer

Diphtheria vaccine

Question 3

Which statement is NOT true regarding the measles vaccine?

Accepted Answer

It is grown in egg culture.

Answer

It is available in a freeze-dried form.

Answer

The reconstituted vaccine must be used within one hour.

Answer

It is administered after 9 months of age.

Question 4

What type of vaccine is the MMR vaccine?

Accepted Answer

Killed

Answer

Live attenuated

Answer

Toxoid

Answer

Subunit

Question 5

The acellular pertussis vaccine contains which of the following components?

Accepted Answer

Filamentous hemagglutinin, pertussis toxin, fimbriae

Answer

Pertactin, filamentous hemagglutinin, pertussis toxin, endotoxin

Answer

Pertactin, filamentous hemagglutinin, fimbriae, endotoxin

Answer

Pertactin, pertussis toxin, fimbriae

Question 6

What is the strain used for the production of the Measles vaccine?

Accepted Answer

Edmonston Zagreb strain

Answer

Jeryl Lynn strain

Answer

17-D strain

Answer

Ankara strain

Question 7

The SA 14-14-2 strain is used in the preparation of which vaccine?

Accepted Answer

JE vaccine

Answer

Typhoid vaccine

Answer

Influenza vaccine

Answer

HPV vaccine

Question 8

Rabies vaccine is prepared from which strain of virus?

Accepted Answer

Fixed Virus

Answer

Street virus

Answer

Wild virus

Answer

All of the above

Question 9

Which of the following diseases are being targeted by developing novel vaccine technologies such as CTL inducing vaccines, Recombinant Adeno-associated Virus Vaccine (rAAV), and Modified Vaccinia Ankara (MVA)?

Accepted Answer

HIV/AIDS

Answer

Tuberculosis

Answer

Malaria

Answer

Leprosy

Question 10

Which vaccine is contraindicated in patients with AIDS?

Accepted Answer

BCG

Answer

DPT

Answer

Rabies

Answer

Measles

Vaccine and Vaccination — MCQs

Vaccine and Vaccination — MCQs

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