The nature of public health research is interdisciplinary, so you may want to search across multiple subject areas:
Starting with Multidisciplinary Databases can be helpful, but requires a more refined search strategy.
PH Partners in Information Access for the Public Health Workforce
A collaboration of U.S. government agencies, public health organizations, and health sciences libraries which provides timely, convenient access to selected public health resources on the Internet.
Connect Google Scholar to the Walden Library so that when you find an appropriate article citation outside of Walden's subscribed databases, you can easily find licensed content via Google Scholar.