New York State Health Education Certification Practice Test

Herd immunity happens when enough people are immune to a disease that its spread from person to person becomes unlikely. When vaccination coverage is high, transmission drops across the whole community, not just among those who are vaccinated. This helps protect individuals who can’t be vaccinated, such as infants or people with certain medical conditions, because the overall amount of circulating virus is reduced. Vaccination benefits both individuals and the community. For an individual, it directly lowers the chance of illness. For the community, it reduces transmission and the likelihood of outbreaks, which is especially important for protecting those who cannot be vaccinated. It doesn’t guarantee that no one will get sick or that all infections will disappear, but it significantly lowers risk and helps shield vulnerable groups.