FRED (A Framework for Reconstructing Epidemiological Dynamics) is an agent-based modeling system for simulating the spatial and temporal patterns of epidemics. FRED was developed by the Public Health Dynamics Laboratory in the Graduate School of Public Health, University of Pittsburgh.
This page shows possible outbreaks following the introduction of a single measles case in selected US cities. The model shows the importance of a high vaccination rate in providing protection for the entire community.
The simulation begins with a single school-age child contracting measles, and shows the possible spread of the disease in the six months after the initial case. Red dots show the location of infectious people, and blue dots show the location of recovered people. If more than a few cases appear, herd immunity has been lost, and the disease spreads easily. If only a few cases appear, herd immunity is still in place.
Two scenarios are shown. In one scenario, it is assumed that 80% of children 6 months old to 15 years old are vaccinated against measles. In the other scenario, it is assumed that 95% of children 6 months old to 15 years old are vaccinated against measles. In most cases, the difference between the 80% coverage scenario and the 95% coverage scenario is quite dramatic. This shows the importance of a high vaccination rate in providing protection for the entire community.
This model is based on several important assumptions such that two doses of the measles vaccine are 97% effective and that those over 15 years old had 95% vaccination rate. The model does not represent the effects of public health responses to a growing epidemic, such as quarantine, increased vaccinations, or school closure. The model is not intended to predict future epidemics, but only to show the possible effects of losing vaccine-induced protective immunity in a community.
This work is supported by the National Institute of General Medical Sciences under MIDAS grant U54GM088491 and by the Bill and Melinda Gates Foundation. The funders had no role in the study design, data collection and analysis, decision to publish, or preparation of the software.