In Leavell's model of prevention, immunization or vaccination is an example of which level?

• A. Primary
• B. Secondary
• C. Tertiary
• D. Quaternary

Answer: (A)

Vaccination is primary prevention because it prevents disease from occurring in the first place by building immunity before exposure. In Leavell and Clark's model, the levels of prevention are organized by when the intervention occurs: primary aims to stop disease before it starts, secondary focuses on early disease detection to avert progression, and tertiary works to lessen complications once disease is already present. Immunization reduces both an individual’s risk and, through herd protection, transmission in the community, lowering the incidence of disease. The other options describe actions taken after disease may be present or are not part of the original three-level framework.