The Australian state of NSW has a history of public health action which predates Federation and continues to this day. In this thesis, I explore three current public health problems in NSW, each of which disproportionately affects a vulnerable sub-population. Three discrete studies are described, and the impact of these studies on public health knowledge, policy and practice in NSW is explored thoroughly. Dental caries is a common childhood health problem in NSW. In the first study, I used qualitative methods to evaluate a novel program established to stabilise existing, and prevent new, caries in children. I sought the views and experiences of program staff and participating parents, and found that both providers and recipients considered that the program components are appropriate, complementary, well delivered and mostly effective. The findings have several implications for oral health promotion practice. Workplace violence is common among health professionals. However, this public health problem has received little research attention in some health care settings. In the second study, I used quantitative methods to scope workplace violence among correctional health and forensic mental health professionals in NSW. The findings show that workplace violence is common in these health workers, although physical abuse is uncommon when compared with health workers practicing in community settings. I make several recommendations for practice in NSW and future research more broadly. Despite being a vaccine preventable infection, pertussis outbreaks occur periodically in NSW. In the third study, I used time series analysis to investigate the potential of real-time monitoring of cough-related emergency department visits among children to provide early warning of pertussis outbreaks. In children, pertussis appears to be an important, but not the sole, driver of cough-related emergency department visits. The findings have implications for future research and the implementation of syndromic surveillance in NSW. The studies included in this thesis have improved our understanding of three contemporary public health problems in NSW. Also, importantly, each applied study has had a tangible impact on the public health landscape in NSW, with findings leading to organisational change in several health services and modifications to a key public health surveillance system. Advisors/Committee Members: Jalaludin, Bin, Public Health & Community Medicine, Faculty of Medicine, UNSW, Jackson Pulver, Lisa, Public Health & Community Medicine, Faculty of Medicine, UNSW.