Diagnostics and the 100-day mission: why preparedness cannot wait.

The 2025 International Panel for Pandemic Surveillance Report and the G7 100-day mission emphasise rapid deployment of diagnostics, but preparatory infrastructure is vital to achieve this goal. Drawing on lateral flow development and haemorrhagic fever case studies, we highlight the requirement for pre-established diagnostic building blocks, including monoclonal antibodies, antigens, biological reference materials and regulatory pathways. Persistent funding imbalances and inequitable global investment threaten timely outbreak response. Sustained preparedness investment, strengthened biobanking and equitable access frameworks will ensure that diagnostics can be delivered within meaningful response timelines.