Vaccine and Vaccination Practice Questions

Q: Which of the following best describes the Hepatitis B vaccine?

Killed vaccine. The Hepatitis B vaccine is a classic example of a **subunit vaccine**, which falls under the broader category of **killed/non-living vaccines**. ### **Explanation of the Correct Answer** The Hepatitis B vaccine currently used is a **recombinant DNA vaccine**. It is produced by inserting the gene for the Hepatitis B surface antigen (HBsAg) into yeast cells (*Saccharomyces cerevisiae*). These cells produce pure HBsAg particles, which are then harvested and purified. Since the vaccine contains only a specific protein component (the surface antigen) and no live viral DNA, it cannot replicate or cause disease. In the context of standard classification (Live vs. Killed), it is categorized as a **killed/inactivated vaccine** because it is non-infectious and non-replicating. ### **Why Other Options are Incorrect** * **A. Live attenuated vaccine:** These contain weakened forms of the whole virus (e.g., MMR, Varicella). Hepatitis B does not use a live virus, making it safe for immunocompromised individuals. * **C. Toxoid:** Toxoids are inactivated bacterial toxins (e.g., Tetanus, Diphtheria). Hepatitis B is a viral infection, not a toxin-mediated bacterial disease. ### **High-Yield Clinical Pearls for NEET-PG** * **First Recombinant Vaccine:** Hepatitis B was the first human vaccine produced using recombinant DNA technology. * **Schedule:** Standard 0, 1, and 6-month dosing. * **Site of Injection:** Always administered **Intramuscularly (IM) in the Deltoid muscle** (adults) or Anterolateral thigh (infants). **Gluteal injection is avoided** due to lower immunogenicity (fat interferes with antigen presentation). * **Protective Titer:** An Anti-HBs antibody titer of **>10 mIU/mL** is considered protective. * **Non-responders:** Individuals who fail to develop antibodies after two full series of vaccinations are termed "non-responders."

Q: Post-exposure vaccination is indicated for which of the following conditions?

Rabies. **Explanation:** The correct answer is **Rabies**. Post-exposure prophylaxis (PEP) is effective when the incubation period of a disease is long enough to allow the vaccine-induced immune response to develop before the pathogen reaches its target organ. **1. Why Rabies is Correct:** Rabies has a variable and often long incubation period (typically 1–3 months). Because the virus travels via retrograde axonal transport to the CNS, there is a "window of opportunity" to administer the vaccine after exposure. The vaccine induces active immunity (neutralizing antibodies) that intercepts the virus before it reaches the central nervous system. In most clinical scenarios, Rabies PEP also includes Rabies Immunoglobulin (RIG) for immediate passive protection. **2. Why Incorrect Options are Wrong:** * **Typhoid:** This is a bacterial infection (Salmonella Typhi) with a relatively short incubation period (7–14 days). Vaccination is used for pre-exposure prophylaxis (travelers or endemic areas) but is ineffective after exposure. * **Mumps:** Mumps is a viral infection where the vaccine is part of the routine MMR schedule. While some live vaccines (like Measles) can be used post-exposure if given within 72 hours, Mumps vaccination does not provide documented protection once exposure has occurred. **3. NEET-PG High-Yield Pearls:** * **Other Post-Exposure Vaccines:** Apart from Rabies, post-exposure vaccination is indicated for **Hepatitis B, Varicella, and Measles**. * **Tetanus:** Often confused with PEP; however, if a wound is prone to tetanus, we administer a booster or TIG based on immunization history. * **Rabies Schedule (Post-exposure):** For non-immunized individuals, the intramuscular (Essen) schedule is **0, 3, 7, 14, and 28 days**. * **Site of Injection:** Rabies vaccine should be given in the **deltoid muscle** (adults) or anterolateral thigh (children). It should **never** be given in the gluteal region as fat reduces vaccine efficacy.

Q: What adjuvant is used in the DPT vaccine?

Aluminum. **Explanation:** **1. Why Aluminum is Correct:** Aluminum salts (specifically **Aluminum hydroxide** or **Aluminum phosphate**) are the most commonly used adjuvants in human vaccines, including the DPT (Diphtheria, Pertussis, and Tetanus) vaccine. An adjuvant is a substance added to a vaccine to enhance the body's immune response to an antigen. Aluminum works via the **"Depot Effect"**—it traps the vaccine antigens at the injection site, allowing for a slow, sustained release. This prolonged exposure recruits more antigen-presenting cells (APCs) and stimulates a stronger Th2 humoral immune response, leading to higher antibody titers. **2. Analysis of Incorrect Options:** * **B. Magnesium & C. Zinc:** These are essential minerals but are not used as adjuvants in standard vaccine formulations. They do not possess the necessary chemical properties to stabilize antigens or stimulate the immune system in this context. * **D. Formaldehyde:** This is a **preservative/inactivator**, not an adjuvant. Formaldehyde is used during the manufacturing process to detoxify bacterial toxins (turning them into toxoids) or to kill viruses, ensuring the vaccine is safe and non-pathogenic. **3. High-Yield Clinical Pearls for NEET-PG:** * **Toxoid Vaccines:** Diphtheria and Tetanus are toxoid vaccines; they always require an adjuvant because toxoids are poorly immunogenic on their own. * **Administration:** Vaccines containing aluminum adjuvants must be administered **intramuscularly (IM)**. If given subcutaneously, they can cause local irritation, granulomas, or "sterile abscesses." * **Freezing:** Aluminum-adjuvanted vaccines should **never be frozen**, as freezing destroys the adjuvant-antigen structure, reducing potency (the "Shake Test" is used to check for this). * **Other Adjuvants:** While Aluminum is the gold standard, newer adjuvants include **AS04** (used in HPV vaccines) and **MF59** (oil-in-water emulsion).

Q: Which of the following is a vaccine for cholera?

Dukoral. ### Explanation **Correct Answer: B. Dukoral** **Dukoral** is an oral, killed whole-cell vaccine containing recombinant Cholera Toxin B-subunit (WC/rBS). It provides protection against *Vibrio cholerae* O1 (both Inaba and Ogawa serotypes) and offers short-term cross-protection against Enterotoxigenic *Escherichia coli* (ETEC) due to the similarity between cholera toxin and ETEC heat-labile toxin. **Analysis of Incorrect Options:** * **A. PPV23 (Pneumococcal Polysaccharide Vaccine):** This is a 23-valent vaccine used to prevent infections caused by *Streptococcus pneumoniae*. It is typically indicated for adults >65 years or individuals with chronic illnesses/asplenia. * **C. Ty21a:** This is a live-attenuated **oral typhoid vaccine** (Salmonella Typhi Ty21a strain). It is administered as enteric-coated capsules on alternate days (Days 1, 3, and 5). * **D. JE-MB Nakayama:** This refers to the **Japanese Encephalitis** Mouse Brain-derived inactivated vaccine. While historically significant, it has largely been replaced by newer vaccines like SA-14-14-2 (live) or Jenvac (inactivated). **High-Yield Clinical Pearls for NEET-PG:** * **Oral Cholera Vaccines (OCVs):** There are three WHO-prequalified OCVs: **Dukoral** (contains B-subunit), **Shanchol**, and **Euvichol** (both are bivalent O1 and O139, but without the B-subunit). * **Shanchol/Euvichol** are preferred for mass vaccination in endemic areas as they are cheaper and do not require a buffer. * **Route:** All modern cholera vaccines are administered **orally**. The older parenteral (injectable) killed vaccine is no longer recommended due to low efficacy and short duration of protection. * **Cross-protection:** Remember that Dukoral is the only one providing significant protection against **Traveler’s Diarrhea (ETEC)**.

Q: Which of the following diseases does NOT currently have an available vaccine?

Dengue fever. **Explanation:** The correct answer is **Dengue fever**. While a vaccine (Dengvaxia) exists and is licensed in some countries, it is not part of the universal or routine immunization schedule in many regions, including India, due to safety concerns regarding "Antibody-Dependent Enhancement" (ADE). In seronegative individuals, the vaccine can act like a primary infection, leading to more severe disease (Dengue Shock Syndrome) upon subsequent natural infection. Therefore, for the purpose of standard medical examinations, it is often categorized as not having a "currently available/routinely used" vaccine compared to the other established options. **Analysis of Options:** * **Yellow Fever:** A highly effective live-attenuated vaccine (**17D strain**) is available. It provides lifelong immunity after a single dose and is mandatory for international travel to endemic zones (Africa/South America). * **Japanese Encephalitis (JE):** Multiple vaccines are available. In India, the live-attenuated **SA-14-14-2 strain** (derived from mice/cell culture) is used under the Universal Immunization Programme (UIP). * **Russian Spring-Summer Encephalitis (RSSE):** Inactivated cell-culture vaccines are available and used routinely in endemic regions of Eastern Europe and Russia. **High-Yield Clinical Pearls for NEET-PG:** 1. **Yellow Fever Vaccine:** Contraindicated in infants <6 months, pregnant women, and immunocompromised individuals. It is grown in **chick embryos**. 2. **JE Vaccine:** In the UIP, two doses are given (9 months and 16–24 months). 3. **Dengue:** The primary challenge in vaccine development is the need to provide equal protection against all four serotypes (DEN 1–4) simultaneously to avoid ADE.

Q: What is the recommended dose of Rubella immunoglobulin?

20 ml. **Explanation:** The correct answer is **20 ml (Option C)**. **Medical Concept:** Rubella (German Measles) is generally a mild disease; however, infection during early pregnancy can lead to **Congenital Rubella Syndrome (CRS)**, causing severe fetal defects. While the primary prevention strategy is live-attenuated vaccination (RA 27/3 strain), post-exposure prophylaxis with **Rubella Immunoglobulin (RIG)** is considered a "last resort" for non-immune pregnant women exposed to the virus who do not wish to undergo therapeutic abortion. The standard recommended dose of RIG is **20 ml** administered intramuscularly. It is important to note that RIG does not guarantee the prevention of fetal infection; it may only suppress clinical symptoms in the mother or prolong the incubation period. **Analysis of Options:** * **A (5 ml) & B (10 ml):** These doses are sub-therapeutic for Rubella prophylaxis. While smaller doses of specific immunoglobulins (like Hepatitis B or Tetanus) are used, Rubella requires a higher volume to achieve necessary antibody titers. * **D (40 ml):** This dose is excessively high and is not supported by standard clinical guidelines. **NEET-PG High-Yield Pearls:** * **Vaccine Strain:** RA 27/3 (Live attenuated, grown in human diploid cells). * **Contraindication:** Pregnancy is an absolute contraindication for the Rubella vaccine. Women should avoid pregnancy for **1 month** (previously 3 months) after vaccination. * **CRS Triad (Gregg’s Triad):** Cataract, Sensorineural deafness, and Cardiac defects (PDA/Pulmonary artery stenosis). * **Diagnosis:** IgM antibodies in the cord blood or infant serum are diagnostic of congenital infection.

Q: Meningococcal vaccine is available for all of the following serogroups, except?

Group B. **Explanation:** The correct answer is **Group B**. The primary reason for the absence of a traditional polysaccharide vaccine for *Neisseria meningitidis* Serogroup B lies in the concept of **molecular mimicry**. The capsular polysaccharide of Serogroup B consists of **α-2,8-linked sialic acid**, which is structurally identical to the sialic acid found on human neural cell adhesion molecules (NCAMs). Because the body recognizes this as "self," the polysaccharide is poorly immunogenic and carries a theoretical risk of inducing autoimmunity. Consequently, standard conjugate or polysaccharide vaccines (like those for A, C, Y, and W-135) cannot be developed for Group B. Instead, newer vaccines for Group B (e.g., Bexsero) utilize **recombinant proteins** rather than capsular polysaccharides. **Analysis of Options:** * **Option A (Group A):** This is a major cause of epidemics in the "Meningitis Belt" of Africa. It is included in both polysaccharide (MPSV4) and conjugate (MCV4) vaccines. * **Option C & D (Group C & Y):** These serogroups are common causes of endemic disease in developed countries. They are highly immunogenic and are standard components of the quadrivalent meningococcal vaccine (A, C, Y, W-135). **NEET-PG High-Yield Pearls:** 1. **Quadrivalent Vaccines:** Cover serogroups **A, C, Y, and W-135**. 2. **Vaccine Type:** Conjugate vaccines (MCV4) are preferred over pure polysaccharide vaccines (MPSV4) because they induce T-cell dependent immunity, providing longer protection and herd immunity. 3. **Group B Vaccine:** Developed using **Reverse Vaccinology**. It targets surface proteins (fHbp, NadA, NHBA) rather than the capsule. 4. **Most common serogroup in India:** Historically Group A, though Group W-135 and others are emerging.

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 vaccine is contraindicated in patients with AIDS?

BCG. **Explanation:** The core concept here is the safety profile of **Live Attenuated Vaccines** in immunocompromised individuals. **Why BCG is the correct answer:** BCG (Bacillus Calmette-Guérin) is a live attenuated vaccine derived from *Mycobacterium bovis*. In patients with AIDS (CD4 count <200 cells/mm³), the immune system cannot contain even the weakened vaccine strain. This can lead to **"Disseminated BCG-osis,"** a life-threatening systemic infection. Therefore, BCG is strictly contraindicated in symptomatic HIV/AIDS patients. **Analysis of Incorrect Options:** * **DPT (Option A):** This is a combination of toxoids (Diphtheria, Tetanus) and a killed/subunit component (Pertussis). Inactivated vaccines are safe in AIDS patients, though their immunogenicity (effectiveness) may be reduced. * **Rabies (Option B):** The modern Rabies vaccine (PCECV/HDCV) is a **killed (inactivated) vaccine**. It is safe to administer and is mandatory for post-exposure prophylaxis regardless of immune status. * **Measles (Option D):** While Measles is a live vaccine, it is a unique exception. WHO and NACP guidelines state that Measles vaccine **should** be given to HIV-infected children unless they are *severely* immunocompromised, because the risk of lethal natural measles outweighs the vaccine risk. However, BCG remains the "most" contraindicated among the choices provided. **NEET-PG High-Yield Pearls:** * **General Rule:** All live vaccines (BCG, OPV, Yellow Fever, Varicella) are generally contraindicated in immunocompromised states. * **The HIV Exception:** Measles and MMR can be given if the patient is not severely immunocompromised. * **Asymptomatic HIV:** In infants born to HIV+ mothers who are asymptomatic, BCG can be given in high-prevalence areas, but once symptoms of AIDS develop, it is contraindicated. * **Avoid OPV:** In a household with an AIDS patient, OPV should be replaced with IPV to prevent vaccine-derived poliovirus shedding.

Question 1

Which of the following best describes the Hepatitis B vaccine?

Accepted Answer

Killed vaccine

Answer

Live attenuated vaccine

Answer

Toxoid

Answer

None of the above

Question 2

Which of the following is/are subunit vaccines?

Accepted Answer

All of the above

Answer

Typhoid Vi

Answer

Haemophilus influenzae type b vaccine (Hib)

Answer

Hepatitis B vaccine

Question 3

Post-exposure vaccination is indicated for which of the following conditions?

Accepted Answer

Rabies

Answer

Typhoid

Answer

Mumps

Answer

None of the above

Question 4

What adjuvant is used in the DPT vaccine?

Accepted Answer

Aluminum

Answer

Magnesium

Answer

Zinc

Answer

Formaldehyde

Question 5

Which of the following is a vaccine for cholera?

Accepted Answer

Dukoral

Answer

PPV23

Answer

Ty 21 a vaccine

Answer

JE-MB Nakayama

Question 6

Which of the following diseases does NOT currently have an available vaccine?

Accepted Answer

Dengue fever

Answer

Yellow fever

Answer

Japanese encephalitis

Answer

Russian spring summer encephalitis

Question 7

What is the recommended dose of Rubella immunoglobulin?

Accepted Answer

20 ml

Answer

5 ml

Answer

10 ml

Answer

40 ml

Question 8

Meningococcal vaccine is available for all of the following serogroups, except?

Accepted Answer

Group B

Answer

Group A

Answer

Group C

Answer

Group Y

Question 9

What is the role of Mg++ in vaccines?

Accepted Answer

Stabilizer

Answer

Preservative

Answer

Adjuvant

Answer

Vehicle

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

On this page

Practice by Chapter

Want unlimited practice?