Vaccine and Vaccination Practice Questions

Q: Which of the following is a live attenuated bacterial vaccine?

BCG vaccine. **Explanation:** The classification of vaccines based on the nature of the antigen is a high-yield topic for NEET-PG. Vaccines are broadly categorized into Live Attenuated, Killed (Inactivated), Subunit/Fractional, and Toxoids. **1. Why BCG is the Correct Answer:** The **BCG (Bacillus Calmette-Guérin)** vaccine is a **Live Attenuated Bacterial** vaccine. It is derived from an attenuated (weakened) strain of *Mycobacterium bovis*. It is unique because most live vaccines used in the universal immunization program are viral; BCG is one of the few bacterial exceptions. **2. Analysis of Incorrect Options:** * **Oral Polio Vaccine (OPV):** This is a live attenuated vaccine, but it is **Viral**, not bacterial. (Sabin strain). * **Haemophilus influenzae type b (Hib):** This is a **Conjugate/Subunit** vaccine. It uses the capsular polysaccharide of the bacteria conjugated to a carrier protein to enhance immunogenicity. * **Whole-cell Pertussis (wP):** This is a **Killed (Inactivated) Bacterial** vaccine. It contains the entire *Bordetella pertussis* organism that has been inactivated by heat or chemicals. **3. NEET-PG High-Yield Pearls:** * **Live Bacterial Vaccines (Mnemonic: "B-Ty"):** **B**CG and Oral **Ty**phoid (Ty21a). * **BCG Administration:** Given intradermally (Left Deltoid) using an Omega/Tuberculin syringe. It produces a characteristic permanent scar. * **Diluent for BCG:** Normal Saline (NS). Reconstituted vaccine must be used within 4–6 hours to prevent contamination and loss of potency. * **Contraindication:** BCG should not be given to individuals with symptomatic HIV or generalized eczema.

Q: All of the following are live vaccines except:

Rabies. **Explanation:** The core concept tested here is the classification of vaccines based on their preparation method. Vaccines are broadly categorized into **Live Attenuated**, **Killed (Inactivated)**, **Subunit/Toxoid**, and **mRNA/Viral Vector** types. **Why Rabies is the correct answer:** The Rabies vaccine used in humans (e.g., Human Diploid Cell Vaccine or Purified Chick Embryo Cell Vaccine) is a **Killed (Inactivated) vaccine**. It contains the inactivated Rabies virus (fixed virus), which is incapable of replication but retains immunogenicity. Because it is killed, it is safe for post-exposure prophylaxis and cannot cause the disease even in immunocompromised individuals. **Why the other options are incorrect:** * **Influenza:** While inactivated (TIV) and recombinant versions exist, the **Intranasal** influenza vaccine is a classic **Live Attenuated** vaccine. In the context of "all of the following are live," Influenza is traditionally categorized as having a live form. * **Yellow Fever:** This is a potent **Live Attenuated** vaccine (specifically the **17D strain**). It is one of the most effective live vaccines available. * **Rubella:** Part of the MMR/MR complex, the Rubella vaccine (specifically the **RA 27/3 strain**) is a **Live Attenuated** vaccine. **NEET-PG High-Yield Pearls:** 1. **Mnemonic for Live Vaccines:** "**BOY** **R**omes **M**y **C**hicken **I**s **V**ery **T**asty" (**B**CG, **O**PV, **Y**ellow Fever, **R**otavirus, **M**MR, **C**hickenpox/Varicella, **I**ntranasal Influenza, **V**ZV, **T**yphoid Ty21a). 2. **Rabies Vaccine Strains:** The "Street virus" is the wild type; the "Fixed virus" (Pasteur strain) is used for vaccine production. 3. **Contraindication:** Live vaccines are generally contraindicated in **pregnancy** and **severely immunocompromised** states (except HIV patients with CD4 >200 for certain vaccines).

Q: Which of the following vaccine types can be safely administered to an immunocompromised child?

Live attenuated vaccines. **Explanation** In the context of immunization, the safety of a vaccine depends on the host's immune status and the vaccine's ability to replicate. **Why Live Attenuated Vaccines are the Correct Answer (in the context of this specific question):** *Note: There appears to be a technical error in the provided key. In standard medical practice, **Live Attenuated Vaccines are generally CONTRAINDICATED** in immunocompromised individuals.* However, if we follow the logic of the provided key (C), it may refer to specific exceptions (like MMR/Varicella in asymptomatic HIV) or a specific exam-frame. **Standard Medical Logic (The "Gold Standard" for NEET-PG):** 1. **Killed (Inactivated), Subunit, and Recombinant Vaccines:** These contain non-living components. Since they cannot replicate, they are **safe** for immunocompromised patients, though the immune response may be suboptimal. 2. **Live Attenuated Vaccines:** These contain weakened but living organisms. In an immunocompromised host, these organisms can replicate unchecked, leading to "vaccine-derived disease" (e.g., disseminated BCG or paralytic polio from OPV). **Analysis of Options:** * **Killed Vaccines (D):** Generally the safest as they contain no live components. * **Subunit (B) & Recombinant (A):** These are highly purified and safe for the immunocompromised. * **Live Attenuated (C):** Usually contraindicated. *High-yield exception:* MMR and Varicella can be given to HIV-infected children if their CD4 count is >15%. **High-Yield Clinical Pearls for NEET-PG:** * **Absolute Contraindication:** Do not give **OPV, BCG, or Yellow Fever** to symptomatic HIV/severely immunocompromised patients. * **Safe Alternatives:** Use **IPV** (Inactivated Polio Vaccine) instead of OPV for household contacts of immunocompromised patients. * **Pregnancy:** Live vaccines (except for specific travel needs like Yellow Fever) are generally contraindicated due to theoretical risk to the fetus.

Q: All are false regarding poliovirus except:

Inactivated vaccine is given intramuscularly. **Explanation:** Poliovirus is a single-stranded RNA virus belonging to the *Picornaviridae* family. Understanding the nuances of its vaccination and epidemiology is high-yield for NEET-PG. **Why Option B is correct:** The **Inactivated Polio Vaccine (IPV)**, also known as the Salk vaccine, consists of formalin-killed virus particles. Because it contains dead virus, it cannot be administered orally (as it would be digested). It is administered via **intramuscular (IM)** or deep subcutaneous injection. In the current National Immunization Schedule of India, fractional doses of IPV (fIPV) are also given intradermally. **Why other options are incorrect:** * **Option A:** In reality, **90–95% of poliovirus infections are asymptomatic** (inapparent infection). Only about 1% of cases result in the classic paralytic poliomyelitis. * **Option C:** This is a distractor. While IPV can be given to children under 3, the primary series starts much earlier. Under the Universal Immunization Programme (UIP), IPV/fIPV is administered at **6 and 14 weeks** of age to provide early systemic immunity. * **Option D:** There are **three distinct serotypes** of poliovirus (Type 1, 2, and 3). Type 2 has been eradicated globally (2015), and Type 3 was declared eradicated in 2019. Most current paralytic cases are caused by Type 1 or vaccine-derived strains. **High-Yield Clinical Pearls for NEET-PG:** * **Sabin vs. Salk:** Sabin (OPV) is live-attenuated, produces local IgA (gut immunity), and can cause Vaccine-Associated Paralytic Polio (VAPP). Salk (IPV) produces systemic IgG and prevents paralysis but does not prevent intestinal reinfection. * **Poliomyelitis:** The virus specifically attacks the **anterior horn cells** of the spinal cord, leading to asymmetrical flaccid paralysis with preserved sensation. * **Specimen of choice:** Stool is the preferred sample for viral isolation.

Q: Which is the strain of the Japanese encephalitis vaccine?

Nakayama strain. **Explanation:** The correct answer is **C. Nakayama strain**. Japanese Encephalitis (JE) vaccines are categorized into inactivated and live-attenuated types. The **Nakayama strain** (and the Beijing-1 strain) are the classic strains used in the production of the mouse-brain-derived inactivated JE vaccine. While many countries have transitioned to the **SA-14-14-2 strain** (a live-attenuated vaccine derived from primary hamster kidney cells), the Nakayama strain remains the historical and frequently tested prototype for inactivated JE vaccines. **Analysis of Incorrect Options:** * **A. Jeryl Lynn strain:** This is the live-attenuated strain used in the **Mumps** vaccine (part of the MMR/MMRV vaccine). * **B. Oka strain:** This is the live-attenuated strain used in the **Varicella** (Chickenpox) and Herpes Zoster vaccines. * **C. 17D strain:** This is the live-attenuated strain used for the **Yellow Fever** vaccine, known for providing long-lasting immunity (up to 10 years or life). **High-Yield Clinical Pearls for NEET-PG:** * **SA-14-14-2:** This is currently the most widely used strain in India’s Universal Immunization Programme (UIP) for the live-attenuated JE vaccine. * **JE Vaccination Schedule (UIP):** Two doses are given—the 1st dose at 9 months (with Measles/MR) and the 2nd dose at 16–24 months (with the DPT booster). * **Vector:** JE is transmitted by the **Culex tritaeniorhynchus** mosquito, which breeds in stagnant water (paddy fields). * **Amplifier Host:** The **Pig** acts as the primary amplifier host for the virus.

Q: Neomycin is used in which of the following vaccines to prevent bacterial contamination?

MMR and IPV. **Explanation:** The correct answer is **B. MMR and IPV**. **1. Underlying Medical Concept:** During the manufacturing of viral vaccines (like MMR and IPV), the viruses are grown in cell cultures or chick embryos. These growth media are highly susceptible to bacterial contamination. To ensure sterility without interfering with viral replication, trace amounts of antibiotics are added. **Neomycin** is the most commonly used aminoglycoside for this purpose. It is specifically used in the **MMR** (Measles, Mumps, Rubella), **IPV** (Inactivated Poliovirus Vaccine), and **Varicella** vaccines. **2. Analysis of Options:** * **Option A (OPV and BCG):** While OPV contains neomycin and streptomycin, **BCG** is a live attenuated bacterial vaccine (M. bovis). Adding antibiotics like neomycin would kill the vaccine strain itself, rendering it ineffective. * **Option C & D (DPT, HPV, Hib):** **DPT** (Toxoids/Killed bacteria) and **Hib** (Polysaccharide conjugate) are bacterial subunit vaccines that do not require cell culture growth, thus neomycin is not a standard additive. **HPV** is a recombinant VLP (Virus-Like Particle) vaccine produced in yeast or insect cells and typically does not contain neomycin. **3. High-Yield Clinical Pearls for NEET-PG:** * **Hypersensitivity:** The presence of neomycin is clinically significant because it is a contraindication for patients with a known **anaphylactic allergy to neomycin**. * **Thiomersal:** A mercury-based preservative used in multi-dose vials (e.g., DPT, Hepatitis B) to prevent fungal/bacterial growth, but it is **absent** in single-dose live vaccines like MMR. * **Other Additives:** Gelatin is often used as a stabilizer in MMR; it is the most common cause of vaccine-associated anaphylaxis.

Q: Whole cell pertussis vaccine used to prevent infection can protect against which of the following?

Both Bordetella pertussis and Bordetella parapertussis. ### Explanation **Correct Answer: C. Both *Bordetella pertussis* and *Bordetella parapertussis*** The **Whole-cell Pertussis (wP)** vaccine is derived from inactivated cultures of *Bordetella pertussis*. While its primary target is *B. pertussis* (the causative agent of classic whooping cough), it provides significant **cross-protection** against *Bordetella parapertussis*. This is because the whole-cell preparation contains a broad array of surface antigens, some of which are shared between the two species. Studies have shown that while the vaccine is more effective against *B. pertussis*, it significantly reduces the clinical severity and incidence of infections caused by *B. parapertussis*. **Analysis of Incorrect Options:** * **Option A:** Incorrect. The vaccine is specifically designed for *B. pertussis*; the protection against *B. parapertussis* is a secondary benefit due to antigenic similarity. * **Option B & D:** Incorrect. The wP vaccine is highly effective (approx. 80-90%) in preventing both mild and severe clinical manifestations of the disease, not just one specific form. **NEET-PG High-Yield Pearls:** * **wP vs. aP:** The Whole-cell vaccine (wP) generally provides better cross-protection against *B. parapertussis* than the Acellular vaccine (aP), as the latter contains only specific purified antigens (like PT, FHA) which may not be present in *B. parapertussis*. * **Adverse Effects:** wP is more reactogenic than aP, commonly causing fever and local reactions. A rare but serious contraindication is **progressive neurological disorders** (e.g., uncontrolled epilepsy). * **Vaccine Type:** It is a **killed/inactivated** bacterial vaccine. * **Schedule:** Administered as part of the Pentavalent/DPT vaccine at 6, 10, and 14 weeks, with boosters at 16-24 months and 5-6 years.

Q: Which of the following is a live attenuated vaccine?

Rabies. **Explanation:** The question asks to identify a **live attenuated vaccine** from the given options. However, there appears to be a discrepancy in the provided key: **Rabies is NOT a live attenuated vaccine; it is an inactivated (killed) vaccine.** In the context of standard medical curriculum and NEET-PG, the options Measles, Oral Polio, and Yellow Fever are all classic examples of live attenuated vaccines. **1. Understanding the Correct Concept (The Discrepancy):** * **Rabies Vaccine:** Modern rabies vaccines (like PCEV or HDCV) used in humans are **Inactivated/Killed** vaccines. Live rabies vaccines are only used in veterinary medicine (oral baits for wildlife) due to the high fatality rate of the disease. * **Live Attenuated Vaccines:** These contain modified pathogens that replicate within the host to induce an immune response without causing the disease. Examples include **Measles, Mumps, Rubella (MMR), OPV (Sabin), Yellow Fever (17D strain), and BCG.** **2. Analysis of Options:** * **A. Measles:** A live attenuated vaccine (Edmonston-Zagreb strain). * **B. Rabies:** An **Inactivated vaccine**. If this is marked "Correct" in your source, it is likely a typographical error or refers to veterinary use. * **C. Oral Polio (Sabin):** A live attenuated vaccine. (Note: Salk/IPV is killed). * **D. Yellow Fever:** A live attenuated vaccine (17D strain). **3. NEET-PG High-Yield Clinical Pearls:** * **Mnemonic for Live Vaccines:** "**B**oy **R**omeo **G**ive **M**y **L**ove **S**picy **V**ictory **T**onight" (**B**CG, **R**ubella/Rotavirus, **G**errman Measles, **M**easles/Mumps, **L**ive Polio, **S**mallpox, **V**aricella, **T**yphoid oral). * **Contraindications:** Live vaccines are generally contraindicated in **pregnancy** and **immunocompromised** states (except HIV patients with CD4 >200 for certain vaccines). * **Yellow Fever:** Provides immunity for life; the certificate is valid after 10 days of vaccination.

Question 1

Which of the following is a live attenuated bacterial vaccine?

Accepted Answer

BCG vaccine

Answer

Oral Polio Vaccine (OPV)

Answer

Haemophilus influenzae type b (Hib) Vaccine

Answer

Whole-cell Pertussis vaccine

Question 2

All of the following are live vaccines except:

Accepted Answer

Rabies

Answer

Influenza

Answer

Yellow fever

Answer

Rubella

Question 3

Which of the following vaccine types can be safely administered to an immunocompromised child?

Accepted Answer

Live attenuated vaccines

Answer

Recombinant vaccines

Answer

Subunit vaccines

Answer

Killed vaccines

Question 4

Passive-active immunity is useful for the exposure of which of the following infections?

Accepted Answer

All of the above

Answer

Rabies

Answer

Hepatitis B

Answer

Varicella-zoster

Question 5

Which of the following diseases is prevented by a live vaccine?

Accepted Answer

Measles

Answer

Cholera

Answer

Smallpox

Answer

Oral Polio

Question 6

All are false regarding poliovirus except:

Accepted Answer

Inactivated vaccine is given intramuscularly

Answer

Most cases are symptomatic

Answer

Inactivated polio vaccines are given to children less than 3 years of age

Answer

Only one type of poliovirus exists

Question 7

Which is the strain of the Japanese encephalitis vaccine?

Accepted Answer

Nakayama strain

Answer

Jeryl Lynn strain

Answer

Oka strain

Answer

17D vaccine

Question 8

Neomycin is used in which of the following vaccines to prevent bacterial contamination?

Accepted Answer

MMR and IPV

Answer

OPV and BCG

Answer

DPT and HPV

Answer

Hib and HPV

Question 9

Whole cell pertussis vaccine used to prevent infection can protect against which of the following?

Accepted Answer

Both Bordetella pertussis and Bordetella parapertussis

Answer

Bordetella parapertussis only

Answer

Mild forms of Bordetella pertussis only

Answer

Only against severe Pertussis

Question 10

Which of the following is a live attenuated vaccine?

Accepted Answer

Rabies

Answer

Measles

Answer

Oral polio

Answer

Yellow fever

Vaccine and Vaccination — MCQs

Vaccine and Vaccination — MCQs

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