Agreement: I Agree Body: Dear Editor Cave and Harnden are right that passive pharmacovigilance is no longer adequate for modern medicines regulation.[1] The burden of adverse drug reactions makes this a patient safety problem, not merely a data-management inconvenience.[2] The unresolved question is how the proposed Health Data Research Service will convert faster access to data into earlier regulatory action. A national data service, as envisaged in the Sudlow Review,[3] could improve linkage,