Which of the following is a live vaccine?

NIMHANS Nursing Officer - 2021

Applied Microbiology & Infection control

Easy

Appeared in: NIMHANS Nursing Officer - 2021

Explanation

BCG (Bacillus Calmette-Guérin) is a classic example of a live attenuated vaccine.
It is prepared from a weakened (attenuated) strain of Mycobacterium bovis, which is closely related to the bacterium that causes human tuberculosis.
Live vaccines work by mimicking a natural infection, which stimulates a robust and long-lasting immune response from the body.

Option B: DPT is a combination vaccine. The Diphtheria (D) and Tetanus (T) components are toxoids (inactivated toxins), and the Pertussis (P) component is made from killed bacteria or just parts of the bacteria (acellular). It does not contain any live organisms.
Option C: The Hepatitis B (Hep-B) vaccine is a recombinant subunit vaccine. It is made using genetic engineering to produce only the surface protein of the virus (HBsAg). It contains no live viral material.
Option D: Tetanus Toxoid (TT) is a toxoid vaccine. It is made from the inactivated toxin produced by the Clostridium tetani bacteria. The vaccine prompts an immune response to the toxin, not the live bacteria.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Classification of Vaccines as background academic context rather than a clinical decision trigger.
Nurses must verify a patient's immune status before administering live vaccines, as they are contraindicated in immunocompromised individuals (e.g., those on chemotherapy, with advanced HIV, or on high-dose steroids) and pregnant women due to the risk of causing actual disease.
Proper cold chain management (typically 2-8°C) is critical for live vaccines to maintain their potency. A break in the cold chain can render the vaccine ineffective.
What if? If a patient needing a vaccine is currently on high-dose steroid therapy, the nurse should hold the live vaccine (like MMR or Varicella) and consult the physician. The vaccine can typically be given after the steroid course is completed and the immune system has recovered.

How to Approach the Question

First, identify the core of the question, which is to find the 'live vaccine' among the options.
Recall the classification of common vaccines. Mentally categorize each option: Is it live, inactivated (killed), toxoid, or subunit/recombinant?
Analyze Option A: BCG. Recall that it's for Tuberculosis and is a classic example of a live attenuated bacterial vaccine.
Analyze the other options to confirm they are not live: DPT (toxoids + killed), Hep-B (recombinant subunit), TT (toxoid).
Conclude that BCG is the only live vaccine in the list, making it the correct answer.

Concept Tested & Keywords

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