Question

In a population, the probability of a susceptible individual getting infected with SARS-CoV-2 is low when a majority of individuals in the population becomes immune to this virus. This phenomenon is known as _______.

• A. innate immunity
• B. adaptive immunity
• C. active immunity
• D. herd immunity

Hint:

Herd immunity occurs when enough people are immune (by vaccination or infection recovery) to block the spread of a disease, thereby protecting even those who are not immune.

Answer 1

The Correct Option is D

Step 1: Understanding the concept
When a significant portion of a population becomes immune to an infectious disease (either through vaccination or previous infection), the overall spread of the pathogen decreases. This indirectly protects even those who are not immune, since the chain of transmission is interrupted. This collective protection is called herd immunity. Step 2: Eliminating wrong options
(A) Innate immunity – This refers to the natural defense system present at birth (e.g., skin barriers, phagocytosis), not population-level protection.
(B) Adaptive immunity – This is acquired after exposure to a pathogen or vaccine, but it applies to individuals, not communities.
(C) Active immunity – This results when the immune system actively produces antibodies after infection or vaccination, but again, it refers to individuals, not populations.
(D) Herd immunity – This is specifically when immunity in a large fraction of the population reduces the overall probability of infection for susceptible individuals.
Therefore, the correct answer is (D) herd immunity.