CDC SVI Fact Sheet

What is Social Vulnerability?

Every community must prepare for and respond to hazardous events, whether a natural disaster like a tornado or disease outbreak, or a human-made event such as a harmful chemical spill. A number of factors, including poverty, lack of access to transportation, and crowded housing may weaken a community’s ability to prevent human suffering and financial loss in a disaster. These factors are known as social vulnerability.

What is the CDC Social Vulnerability Index?

ATSDR’s Geospatial Research, Analysis & Services Program (GRASP) created databases to help emergency response planners and public health officials identify and map communities that will most likely need support before, during, and after a hazardous event.

CDC’s SVI uses U.S. Census data to determine the social vulnerability of every census tract. Census tracts are subdivisions of counties for which the Census collects statistical data. The SVI ranks each tract on 15 social factors, including poverty, lack of vehicle access, and crowded housing, and groups them into four related themes. Maps of the four themes are shown in the figure below. Each tract receives a separate ranking for each of the four themes, as well as an overall ranking.

How Can the CDC SVI Help Communities be Better Prepared?

The SVI can help public health officials and local planners better prepare for and respond to emergency events like hurricanes, disease outbreaks, or exposure to dangerous chemicals.

Hurricane Sandy ‐ Breezy Point, NY

Hurricane Sandy ‐ Breezy Point, NY Photographer – Pauline Tran

Range of vulnerability in Gwinnett County, Georgia.

Maps show the range of vulnerability in Gwinnett County, Georgia for the four themes

CDC SVI Databases and Maps Can be Used to:

  • Estimate the amount of needed supplies like food, water, medicine, and bedding.
  • Help decide how many emergency personnel are required to assist people.
  • Identify areas in need of emergency shelters.
  • Plan the best way to evacuate people, accounting for those who have special needs,such as people without vehicles, the elderly, or people who do not understand English well.
  • Identify communities that will need continued support to recover following an emergency or natural disaster.

For more information, please contact CDC’s SVI Coordinator (

Page last reviewed: December 6, 2019