What term describes the situation when enough people in a population are vaccinated that the spread of disease to unvaccinated individuals becomes unlikely?

What term describes the situation when enough people in a population are vaccinated that the spread of disease to unvaccinated individuals becomes unlikely?

• A. Herd Immunity
• B. Community Immunity
• C. Population Immunity
• D. Group Immunity

Answer: (A)

Herd immunity occurs when enough people in a population are immune to a disease, usually through vaccination, so the spread to unvaccinated individuals becomes unlikely. When a large portion is immune, there are fewer susceptible hosts, which lowers the effective reproduction number and can stop transmission chains. This protection extends to those who cannot be vaccinated or for whom vaccines are less effective. This is the standard epidemiological term for this population-level protection. Other terms like community immunity, population immunity, or group immunity aren’t the standard way to describe this specific phenomenon, even though they’re sometimes used informally. The exact threshold depends on how contagious the disease is, but the core idea is that higher immunity in the group reduces the chance of spread to those who are not immune.

Herd immunity occurs when enough people in a population are immune to a disease, usually through vaccination, so the spread to unvaccinated individuals becomes unlikely. When a large portion is immune, there are fewer susceptible hosts, which lowers the effective reproduction number and can stop transmission chains. This protection extends to those who cannot be vaccinated or for whom vaccines are less effective. This is the standard epidemiological term for this population-level protection. Other terms like community immunity, population immunity, or group immunity aren’t the standard way to describe this specific phenomenon, even though they’re sometimes used informally. The exact threshold depends on how contagious the disease is, but the core idea is that higher immunity in the group reduces the chance of spread to those who are not immune.