Nelson’s research interests include social determinants of health, HIV risk factors, transmission and impacts, HIV care, access to healthcare services, mental health, migrants' health, disability, and social and emotional wellbeing.

Nelson is a researcher at the Centre for Public Health, Equity and Human Flourishing (PHEHF), Torrens University Australia. He has been involved in 20 research projects and was/is the principal investigator for 13 projects. His research projects on HIV-related topics have involved various marginalised groups of people living with HIV (PLHIV), such as mothers, husbands, children, transgender women, men who have sex with men, motor taxi drivers, clients of female sex workers, and parents/caregivers of AIDS-orphaned children. Other population groups involved in his research projects are healthcare professionals, families of children with disabilities, and HIV-related policy makers. He has research networks and collaborations with other researchers from Australia and other countries, including Indonesia, the Netherlands, Tanzania, and the UK. He also has a global research network through his involvement in the Global Burden of Disease Network. Some of his current publications that have attracted tens of thousands of views and downloads are on HIV stigma and discrimination against PLHIV. Nelson and a team of researchers at PHEHF have just completed a project on the social and emotional wellbeing of Indigenous children and adolescents in CANZUS nations, which was funded by Wellbeing SA. Currently, he leads two research projects investigating the impacts of parental migration on the left behind children in Indonesia and the mental health impacts of HIV on adolescents living with HIV.