What is herd immunity?

Herd immunity is achieved when a significant portion of a population is vaccinated, which decreases the overall spread of contagious diseases. This concept is crucial because when enough individuals are immune—whether through vaccination or previous infections—the likelihood of the disease spreading is markedly reduced. This protects those who are unvaccinated, such as those with certain health conditions or individuals for whom vaccination is not recommended, creating a shield within the community.

The importance of this collective immunity not only safeguards vulnerable populations but also contributes to the overall health of society by limiting outbreaks and protecting healthcare resources. This explains why the option referring to a significant portion vaccinated as the foundation of herd immunity is accurate and reflects the public health strategy aimed at controlling infectious diseases.