Vulnerability Index

The Vulnerability Index is a tool for identifying and prioritizing people who are homeless and living on the streets for housing according to the fragility of their health. It identifies the most vulnerable individuals through a ranking system that takes into account mortality risk factors and the duration of homelessness. This ranking, along with a by-name registry of the community’s unsheltered homeless population, allows communities to prioritize permanent supportive housing and other supports to those with the most severe health risks.

Problem or Challenge:

According to the 2010 U.S. Department of Housing and Urban Development’s Annual Homeless Assessment Report, nearly 470,000 people are living on the streets and in shelters on any given night in the United States. Homelessness contributes to illness through a variety of factors, including physical and psychological stress, exposure to the elements, exposure to bacteria and viruses, lack of access to sanitation and hygiene facilities, poor nutrition, sleep deprivation, and lack of access to preventive health care.  The death rate (deaths per year) for people experiencing homelessness is about four times greater than the rate for the general population, and among young men experiencing homelessness, the rate is even higher.  On average, adults who are experiencing homelessness die twenty years earlier than do non-homeless adults. 

In Boston, a wave of unattended deaths of homeless people on the streets (street deaths) during the winter of 1998–1999 generated wide public concern and prompted the Massachusetts Department of Public Health to convene a task force to investigate the deaths.   In 1998, Dr. Stephen Hwang and his colleague, Dr. Jim J. O’Connell, President of Boston's Health Care for the Homeless Program, published their research that identified the specific health conditions that resulted in a greater mortality risk when combined with the experience of homelessness.  The doctors proceeded to find people on the streets of Boston who suffered from any of those health conditions, forming a high risk cohort of 119 such individuals in 2000.  One-third of the individuals in the high-risk cohort died within three years, creating what Dr. O’Connell refers to as “the highest known mortality rate in America.” The factors shared by those in the high-risk cohort form the basis of the scoring for the Vulnerability Index.  For individuals who have been homeless for at least six months, one or more of the following markers place them at heightened risk of mortality: 

  1. more than three hospitalizations or emergency room visits in a year
  2. more than three emergency room visits in the previous three months
  3. aged 60 or older
  4. cirrhosis of the liver
  5. end-stage renal disease
  6. history of frostbite, immersion foot, or hypothermia
  7. HIV+/AIDS
  8. tri-morbidity: co-occurring psychiatric, substance abuse, and chronic medical condition


The Vulnerability Index is administered in the form of a survey, which captures a homeless individual’s health and social status. It identifies the most vulnerable persons through a ranking system which takes into account the mortality risk factors identified in Dr. Jim O’Connell’s research and the duration of a person’s homelessness. This ranking helps communities identify and prioritize referrals to permanent supportive housing and other supports.

Common Ground, a provider of housing and services to prevent and end homelessness, collaborated with Dr. Jim O’Connell and the Center for Urban Community Services to develop the prototype survey that was later adapted to become the Vulnerability Index. The survey was first used by Common Ground in the summer of 2007 as part of the agency’s Street to Home outreach and housing placement program in New York City, because the organization wanted to ensure that teams of outreach workers prioritized into permanent supportive housing those who had been on the streets the longest and those whose health was the most fragile. Later that year, Common Ground was invited to provide technical assistance for using the Vulnerability Index and conducting a Registry Week in Los Angeles County’s infamous Skid Row. This project became known as Project 50. Over the next year, Common Ground helped Santa Monica, New Orleans, Washington, DC, Fort Worth, Portland, and Nashville adopt the Vulnerability Index.  As communities used this tool and refined the Registry Week process, they found it provided a heightened awareness and renewed sense of urgency around housing their most vulnerable neighbors.  In July 2010, Common Ground launched the 100,000 Homes Campaign, a movement to find and house 100,000 of the country’s most vulnerable and chronically homeless individuals and families in three years.  In 2011 Common Ground created a new non-profit organization, Community Solutions, a new organization aimed at strengthening communities to end homelessness nationwide.  Community Solutions provides ongoing leadership for the 100,000 Homes Campaign, and the Vulnerability Index is a critical tool for the Campaign’s approach, which has been used in dozens of communities in the United States, as well as in Canada and Australia.  

Implementation Steps/Tips: 

The Vulnerability Index, an on-line scoring database, and training on how to use it to find and house the most long-term and vulnerable people experiencing homelessness, are available to all communities that enroll in the 100,000 Homes Campaign. (To enroll, fill out the on-line enrollment formand a representative will contact you.)  

Once community leaders enroll in the campaign, they are coached through different options for adapting the Vulnerability Index. Most communities plan to conduct a Registry Week and teach volunteers how to survey people on the streets or in shelters using the Vulnerability Index. Some communities integrate the survey tool into their standard outreach procedures. Entire states have integrated the Vulnerability Index into their HMIS system. (The campaign team can work with you to find what works best for your situation.) 


Common Ground has observed that putting names and faces – and now medical conditions – to formerly anonymous individuals who are homeless and living on the streets inspires action. The commitment of permanent supportive housing resources and the expedited housing placement of people who are medically fragile have been the direct, concrete results of the use of the Vulnerability Index.  As of March 2012, 62 communities enrolled in the 100,000 Homes Campaign had completed over 30,000 Vulnerability Index Surveys and provided data to the 100,000 Homes Campaign.  Information summarizing these survey results is available in a report posted on the 100,000 Homes Campaign website. As of September 2012, survey results have been used to help over 20,000 people move from the streets and shelters into permanent supportive housing in more than 150 communities.  To see if the Vulnerability Index is being used in your community, find your community on this map and contact the point person by clicking on the red dot.

Contact Info for Follow-up:

Community Solutions:

100,000 Homes Campaign:

Related Profiles

Evidence-Based Practice: Permanent Supportive Housing

Evidence-Based Practice: Housing First