Last Sunday saw an overwhelming response to the AstraZeneca Covid-19 vaccine registration opt-in system, when all 268,000 vaccination slots were taken up in about three hours. The process was a unique opportunity to test public responsiveness to a parallel vaccine rollout. What was discovered about this state-based, vaccine-specific, opt-in system? Melisa Idris and Sharaad Kuttan speak to independent Health Policies Specialist, Dr Khor Swee Kheng.