Dr. Siobhan Johnstone

Siobhan Johnstone is a South African infectious disease epidemiologist whose work centres on the burden, aetiology, and prevention of communicable diseases in sub-Saharan Africa. Her research integrates hospital-based surveillance, community surveys, and advanced laboratory diagnostics to strengthen evidence for public health policy. She is closely involved in multicentre initiatives such as the African Network for Improved Diagnostics, Epidemiology and Management of Common Infectious Agents, supporting regional capacity in pathogen detection and outbreak preparedness.

Johnstone’s scholarship focuses strongly on diarrhoeal and respiratory diseases, particularly among vulnerable populations including people living with HIV and young children. Her case-control and surveillance studies clarify pathogen-specific causes of moderate to severe diarrhoea and severe acute respiratory infections, highlighting differences by HIV status and healthcare access. This work has informed diagnostic guidelines, revealed surveillance gaps, and underscored inequities between community burden and facility-based reporting.

More recent contributions examine antimicrobial use and resistance patterns across multiple African settings, as well as COVID-19 vaccine effectiveness during successive variant waves in South Africa. By combining epidemiological modelling with real-world clinical and insurance data, her research provides actionable insights on vaccine protection, antibiotic stewardship, and the indirect effects of public health interventions, reinforcing evidence-based strategies to reduce severe infectious disease outcomes.