Vaccine and Vaccination — MCQs

Vaccine and Vaccination Indian Medical PG Practice Questions and MCQs

Question 81: The presence of which of the following factors in viruses makes protective vaccines a possibility?

A. Lipids
B. Protein coat (Correct Answer)
C. Enzymes
D. Polysaccharide

Explanation: ***Protein coat*** - The **protein coat** (capsid) of viruses contains **antigenic proteins** that can be recognized by the host immune system. - Vaccines work by exposing the immune system to these viral proteins, stimulating the production of **antibodies** and memory cells for future protection. *Lipids* - While some viruses have a **lipid envelope**, lipids themselves are generally **poor antigens** and do not effectively stimulate a protective immune response on their own. - The immune response against enveloped viruses is primarily directed at the **glycoproteins** embedded within the lipid envelope, not the lipids themselves. *Enzymes* - Viruses contain various enzymes (e.g., reverse transcriptase, RNA polymerase) essential for their replication, but these are typically **intracellular targets**. - **Enzymes** are not usually present on the viral surface in an exposed manner that would consistently trigger a protective antibody response. *Polysaccharide* - **Polysaccharides** are common components of bacterial capsules but are generally **not significant components** of viral structure. - Viruses are primarily composed of nucleic acids and proteins, and the immune response to viruses rarely involves polysaccharides.

Question 82: A microbiologist wants to develop a vaccine for prevention of attachment of diarrhoeagenic E.coli to the specific receptors in the gastro-intestinal tract. All of the following fimbrial adhesions would be appropriate vaccine candidates except -

A. P1-Pili (Correct Answer)
B. K 88
C. CFA-1
D. CS-2

Explanation: ***P1-Pili*** - **P1-pili** (also known as P-fimbriae or Pap-pili) are primarily associated with **uropathogenic *E. coli*** causing **urinary tract infections**, not diarrhoeagenic *E. coli* in the gastrointestinal tract. - A vaccine targeting P1-pili would therefore not be relevant for preventing gastrointestinal attachment. *K 88* - **K88 fimbriae** are well-known **adhesins** found in certain strains of **enterotoxigenic *E. coli*** (ETEC) that colonize the gut and cause diarrhoea, especially in piglets. - Targeting K88 would be an appropriate strategy for a vaccine against diarrhoeagenic *E. coli*. *CFA-1* - **Colonization Factor Antigen I (CFA/I)** is a major **fimbrial adhesin** expressed by human **enterotoxigenic *E. coli*** (ETEC) strains. - CFA/I mediates bacterial attachment to intestinal epithelial cells and is a critical virulence factor, making it a suitable vaccine candidate. *CS-2* - **Colonization Factor Antigen II (CFA/II)**, which includes subunits like **CS-2** (CS for "coli surface"), is another important **fimbrial adhesin** found in human **enterotoxigenic *E. coli*** (ETEC). - CS-2 contributes significantly to ETEC's ability to colonize the small intestine and cause diarrhoea, making it a strong vaccine candidate.

Question 83: Adjuvants given along with antigens are going to

A. reduce the antigenicity
B. increase antigenicity (Correct Answer)
C. reduce the toxigenicity
D. increase toxigenicity

Explanation: ***increase antigenicity*** - Adjuvants are substances added to vaccines to **enhance the immune response** to the co-administered antigen. - They work by various mechanisms, such as forming an antigen depot, activating antigen-presenting cells, and stimulating cytokine production, all leading to a **stronger and more prolonged immune response**. *reduce the antigenicity* - This statement is incorrect as adjuvants are specifically designed to **potentiate, not diminish**, the immune response to an antigen. - Reducing antigenicity would counteract the primary purpose of vaccination, which is to induce protective immunity. *reduce the toxigenicity* - Adjuvants generally do not directly impact the **toxigenicity** of an antigen, which refers to its ability to produce toxins. - While some vaccines detoxify bacterial toxins (e.g., toxoids), this is a separate process from the action of adjuvants that boost immune recognition. *increase toxigenicity* - This is incorrect; adjuvants are not intended to make an antigen more toxic. - Their role is to enhance immunogenicity safely, and increasing toxicity would be counterproductive and harmful.

Question 84: Conjugate vaccines are available for the prevention of invasive disease caused by all of the following except

A. Strep pneumoniae
B. H influenzae
C. N. Meningitidis (group B) (Correct Answer)
D. N. Meningitidis (group C)

Explanation: ***N. Meningitidis (group B)*** - While conjugate vaccines are available for several serogroups of *N. meningitidis*, a **polysaccharide-protein conjugate vaccine** for **serogroup B** has been challenging to develop due to its **less immunogenic capsule** and antigenic mimicry with human tissues. - Currently, available vaccines against **meningococcal serogroup B** are **recombinant protein-based vaccines** (e.g., Bexsero, Trumenba), not traditional polysaccharide-protein conjugate vaccines. *Strep pneumoniae* - **Pneumococcal conjugate vaccines (PCVs)**, such as PCV13 and PCV15, effectively prevent invasive disease caused by *Streptococcus pneumoniae* in both children and adults. - These vaccines conjugate **polysaccharide capsular antigens** to carrier proteins, enhancing immunogenicity, especially in young children. *H influenzae* - The **Haemophilus influenzae type b (Hib) conjugate vaccine** is highly effective in preventing invasive Hib disease, including meningitis and epiglottitis. - This vaccine links the **Hib polysaccharide capsule** to a protein carrier, eliciting a T-cell-dependent immune response. *N. Meningitidis (group C)* - **Meningococcal conjugate vaccines** are widely available and routinely used to prevent invasive disease caused by *Neisseria meningitidis* serogroup C. - These vaccines include **monovalent (e.g., MenC)** and **quadrivalent (e.g., MenACWY)** formulations that target serogroup C.

Question 85: MW vaccine is prepared from:

A. Mycobacterium indicus pranii (Correct Answer)
B. Mycobacterium welchii
C. Mycobacterium bovis
D. Mycobacterium tuberculosis

Explanation: ***Mycobacterium indicus pranii*** - The MW vaccine, also known as the **M. indicus pranii (MIP) vaccine**, is derived from heat-killed *M. indicus pranii* cells. - It is currently being explored as an immunomodulator and vaccine candidate for **leprosy** and **tuberculosis**. *Mycobacterium welchii* - This is an incorrect name; the correct species is *Clostridium perfringens*, previously known as *Bacillus welchii*. - *Clostridium perfringens* is a **gram-positive, anaerobic bacterium** that causes gas gangrene and food poisoning, and is not used in vaccine production for tuberculosis or leprosy. *Mycobacterium bovis* - *Mycobacterium bovis* is the bacterium used to produce the **BCG vaccine** (Bacillus Calmette-Guérin). - The BCG vaccine is primarily used to prevent **tuberculosis**, particularly severe forms in children. *Mycobacterium tuberculosis* - This is the primary causative agent of **tuberculosis** in humans. - A vaccine derived directly from live, virulent *M. tuberculosis* is not used due to its pathogenicity and the risk of causing disease.

Question 86: What is the primary advantage of using live attenuated vaccines?

A. They are effective with single doses
B. They are cheaper to produce
C. They provide stronger, longer-lasting immunity (Correct Answer)
D. They require fewer booster shots

Explanation: ***They provide stronger, longer-lasting immunity*** - Live attenuated vaccines mimic natural infection, leading to a robust immune response involving both **humoral** and **cell-mediated immunity**. - This comprehensive immune activation often results in **lifelong protection** with fewer doses, similar to immunity gained from natural infection. *They are cheaper to produce* - The production of live attenuated vaccines can be complex due to the need for careful **attenuation** and strict quality control, which can be costly. - While some attenuated vaccines might be cost-effective in the long run due to fewer doses, initial production costs are not their primary advantage. *They are effective with single doses* - While many live attenuated vaccines are highly effective with a single dose, not all are; some, like MMR, still require a second dose for optimal protection. - The effectiveness with fewer doses is rather a consequence of the strong immune response, not a standalone advantage over the quality of immunity. *They require fewer booster shots* - This is a direct benefit stemming from the **strong, long-lasting immunity** conferred by live attenuated vaccines. - However, the primary advantage is the quality and duration of the immune response itself, which in turn reduces the need for frequent boosters.

Question 87: In the context of viral diseases, which of the following is a key advantage of live attenuated vaccines over inactivated vaccines?

A. Safe for use in immunocompromised patients.
B. Elicits a robust antibody response without risk of reversion.
C. Preferred for mass vaccination during an outbreak.
D. Induces long-term immunity with a single dose. (Correct Answer)

Explanation: ***Induces long-term immunity with a single dose*** - **Live attenuated vaccines** stimulate a more comprehensive immune response, mimicking natural infection, leading to stronger and **longer-lasting immunity** often with a single dose. - This robust response typically involves both **humoral and cellular immunity**, providing excellent protection. *Safe for use in immunocompromised patients* - **Live attenuated vaccines** are generally **contraindicated in immunocompromised individuals** due to the risk of the attenuated virus replicating and causing disease. - **Inactivated vaccines**, which do not contain live virus, are safer for this population. *Elicits a robust antibody response without risk of reversion* - While live attenuated vaccines do elicit a robust immune response, there is a **small risk of the attenuated virus reverting to a virulent form**, especially in populations with low vaccine coverage. - **Inactivated vaccines** do not carry this risk as the virus is killed and cannot replicate or revert. *Preferred for mass vaccination during an outbreak* - While sometimes used, **live attenuated vaccines** require careful handling, cold chain maintenance, and may have contraindications that complicate mass vaccination efforts during an outbreak. - **Inactivated vaccines** can sometimes be easier to administer during a large-scale outbreak due to their stability and perceived safety profile in diverse populations.

Question 88: Which type of vaccine contains live, attenuated organisms?

A. MMR vaccine (Correct Answer)
B. Hepatitis B vaccine
C. Polysaccharide vaccine
D. Inactivated influenza vaccine

Explanation: ***MMR vaccine*** - The **MMR (Measles, Mumps, Rubella) vaccine** is a classic example of a **live-attenuated vaccine**, using weakened forms of the viruses. - Live-attenuated vaccines generally provide long-lasting immunity with a strong immune response, often after just one or two doses. *Hepatitis B vaccine* - The **Hepatitis B vaccine** is a **recombinant vaccine**, meaning it contains only a specific antigenic component (the surface antigen) of the virus. - It does not contain the whole live or inactivated virus, but rather a manufactured protein that elicits immunity. *Polysaccharide vaccine* - **Polysaccharide vaccines**, such as the pneumococcal polysaccharide vaccine, consist of **purified capsular polysaccharides** from bacteria. - These are **subunit vaccines** that target specific components of the pathogen but do not contain live organisms. *Inactivated influenza vaccine* - The **inactivated influenza vaccine** contains **killed influenza viruses** or viral components that have been chemically or physically inactivated. - Since the viruses are inactivated, they cannot replicate or cause disease, distinguishing them from live-attenuated vaccines.

Question 89: What is the specific protein content of the malaria vaccine RTS,S/AS01?

A. Gametocytic protein
B. Polysaccharide sheath
C. Lipoprotein envelope
D. Sporozoite protein (Circumsporozoite protein) (Correct Answer)

Explanation: ***Sporozoite protein*** - The RTS,S/AS01 vaccine specifically targets the **circumsporozoite protein (CSP)** from the *Plasmodium falciparum* sporozoite stage. - This design aims to prevent **malaria infection** by blocking the parasite before it can infect liver cells. *Gametocytic protein* - Vaccines targeting gametocytic proteins are in development but are designed to block **transmission** of malaria, not prevent initial infection. - They aim to induce antibodies that neutralize gametes within the mosquito, preventing the parasite's sexual reproduction. *Polysaccharide sheath* - **Polysaccharide components** are common in bacterial vaccines (e.g., pneumococcal), but not the primary immunogen in RTS,S, which is a protein-based vaccine. - *Plasmodium* parasites do not possess a significant polysaccharide sheath that serves as a primary vaccine target in this context. *Lipoprotein envelope* - **Lipoprotein envelopes** are characteristic of some viruses (e.g., influenza, HIV), not typically the primary antigen of interest for *Plasmodium falciparum* sporozoites. - While there are lipid components in the parasite, the specific targeted antigen for RTS,S is a **protein**.

Question 90: What is the serum marker after Hepatitis B vaccination?

A. Anti-HBs (Correct Answer)
B. Anti-HBe
C. Anti-HBc
D. HBs antigen

Explanation: **Anti-HBs** - The Hepatitis B vaccine contains **HBsAg** (Hepatitis B surface antigen), which stimulates the immune system to produce **antibodies against HBsAg (Anti-HBs)**. - The presence of **Anti-HBs** indicates successful vaccination and immunity to Hepatitis B infection. *Anti-HBe* - **Anti-HBe** antibodies develop during an acute or chronic Hepatitis B infection and indicate a decrease in viral replication and infectivity. - This marker is not associated with vaccination. *Anti-HBc* - **Anti-HBc** (antibodies against Hepatitis B core antigen) is produced during an active or past Hepatitis B infection, but not as a result of vaccination. - It signifies exposure to the **core protein** of the virus. *HBs antigen* - **HBs antigen (HBsAg)** is a surface protein of the Hepatitis B virus that indicates active acute or chronic infection. - It is the antigen used in the vaccine to stimulate an immune response, but it is not a marker of immunity after vaccination.

Practice by Chapter

Principles of Immunization

Practice Questions

Types of Vaccines

Practice Questions

Vaccine Development and Production

Practice Questions

Routine Immunization Schedule

Practice Questions

Adverse Events Following Immunization

Practice Questions

Cold Chain and Vaccine Delivery

Practice Questions

New Vaccine Technologies

Practice Questions

Vaccination in Special Populations

Practice Questions

Herd Immunity and Population Protection

Practice Questions

Anti-vaccination Movement and Hesitancy

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National Immunization Programs

Practice Questions

Future of Vaccines

Practice Questions

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