Vulnerable populations include patients who are racial or ethnic minorities, children, elderly, socioeconomically disadvantaged, underinsured or those with certain medical conditions. Members of vulnerable populations often have health conditions that are exacerbated by unnecessarily inadequate healthcare. (National Institutes of Health)
Combine the above terms with terms like these:
**Note that you will find resources that refer to immigrant populations as 'illegal aliens.' This term is offensive and there is now a push from the Federal Government to remove this terms from legislation.