An epidemiologist is modeling the spread of a virus. Initially, 60% of the population is susceptible. After a vaccination campaign, the susceptible population decreases by 25%. What percentage of the total population is now susceptible?

Thu, 30 Apr 2026 10:55:36 +0000

**Understanding How Vaccination Shifts Population Susceptibility—And Why It Matters** Why are public health discussions about vaccination uptake increasing across U.S. communities? For many, the answer lies in the quiet but powerful work of epidemiologists modeling how diseases spread—and how interventions reshape those patterns. At the heart of this is a fundamental metric: what percentage of the population remains vulnerable to a virus after a vaccination campaign? Understanding this shift reveals vital insights into community protection and long-term epidemic control. The starting point is a widely recognized statistic: 60% of the population is initially susceptible to a virus. This figure reflects not just biology, but also demographics, exposure risk, and prior immunity. With growing access to vaccines, the next pivotal question emerges: how effective is the campaign in reducing that vulnerability? When a vaccination effort successfully protects individuals, the susceptible population shrinks—yet not by an arbitrary amount. **Analyzing the 25% Decrease: A Clear Deliberate Shift**