Which vaccine, after administration, forms blisters, heals by itself, and forms a permanent scar mark?

NORCET 1 - 2020

Pharmacology

Easy

Appeared in: NORCET 1 - 2020

Explanation

The Bacillus Calmette-Guérin (BCG) vaccine is a live attenuated vaccine used for protection against tuberculosis.
It is administered intradermally, typically in the left upper arm (deltoid region).
This route of administration leads to a characteristic local skin reaction: a small papule develops, which may ulcerate (blister) and then slowly heals over several weeks to months.
The healing process results in a permanent, slightly depressed scar, which serves as a visible marker of successful vaccination.

Option B: The MMR (Measles, Mumps, Rubella) vaccine is administered subcutaneously and does not cause the characteristic ulceration and permanent scarring described in the question. Local reactions are typically mild and transient.
Option C: The DPT/DT vaccine is given intramuscularly. While it can cause local pain, redness, and swelling, it does not form a blister or leave a permanent scar.
Option D: The Polio vaccine is given either orally (OPV) or as an injection (IPV). OPV has no injection site, and IPV (intramuscular/subcutaneous) does not cause blistering or scarring.

Visual 1: Diagram - A series of images showing the progression of the BCG vaccine reaction on the skin, from the initial papule to the ulcer and finally the healed permanent scar. This helps visualize the key identifier in the question.
Visual 2: Chart - The National Immunization Schedule (India), highlighting the BCG vaccine, its recommended age of administration (at birth), route (intradermal), and site (left upper arm).

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain The concept tested is the identification of a vaccine based on its specific post-administration local reaction, particularly the formation of a permanent scar as background academic context rather than a clinical decision trigger.
A nurse must be able to recognize the normal evolution of a BCG reaction to differentiate it from an adverse reaction or infection, and to reassure parents.
The presence of a BCG scar is often checked as presumptive evidence of prior vaccination, especially when vaccination records are unavailable. This is a common practice in countries where tuberculosis is endemic.
What if? If a child does not develop a scar after BCG vaccination, it does not necessarily mean the vaccine failed. The WHO does not recommend revaccination, as some level of immunity may still have developed. The nurse's role is to educate the parents and follow local public health guidelines.

How to Approach the Question

First, read the question carefully and identify the key descriptive words: 'blisters', 'heals by itself', and 'permanent scar mark'.
This is a factual recall question. Access your knowledge about the common vaccines listed in the options.
Consider each option one by one. Think about the type of vaccine, its route of administration, and its known side effects or local reactions.
Recall that the BCG vaccine is given intradermally and is famous for leaving a permanent scar.
Eliminate the other options: MMR (subcutaneous, no scar), DPT (intramuscular, no scar), and Polio (oral or injection, no scar).
Confirm that BCG is the only vaccine among the choices that matches all the descriptors in the question.

Concept Tested & Keywords

Concept Tested: The concept tested is the identification of a vaccine based on its specific post-administration local reaction, particularly the formation of a permanent scar.
Stem keywords: vaccine, administration, blisters, heals, permanent scar
Lead-in keywords: Which
Negative lead-in flag: false

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