Assessing recording delays in general practice records to inform near real-time vaccine safety surveillance using the Clinical Practice Research Datalink (CPRD)

Purpose: Near real-time vaccine safety surveillance (NRTVSS) is an option for post-licensure vaccine safety assessment. NRTVSS requires timely recording of outcomes in the database used. Our main objective was to examine recording delays in the Clinical Practice Research Datalink (CPRD) for outcomes of interest for vaccine safety to inform the feasibility of NRTVSS using these data. We also evaluated completeness of recording and further assessed reporting delays for hospitalized events in CPRD. Methods: We selected Guillain–Barré syndrome (GBS), Bell's palsy (BP), optic neuritis (ON) and febrile seizures (FS), from January 2005 to June 2014. We assessed recording delays (e.g. due to feedback from specialist referral) in stand-alone CPRD by comparing the event and system dates and excluding delays >1 year. We used linked CPRD-hospitalization data to further evaluate delays and completeness of recording in CPRD. Results: Among 51 220 patients for the stand-alone CPRD analysis (GBS: n = 830; BP: n = 12 602; ON: n = 1720; and FS: n = 36 236), most had a record entered within 1 month of the event date (GBS: 73.6%; BP: 93.4%; ON: 76.2%; and FS: 85.6%). A total of 13 482 patients, with a first record in hospital, were included for the analysis of linked data (GBS: n = 678; BP: n = 4060; ON: n = 485; and FS: n = 8321). Of these, <50% had a record in CPRD after 1 year (GBS: 41.3%; BP: 22.1%; ON: 22.4%; and FS: 41.8%). Conclusion: This work shows that most diagnoses in CPRD for the conditions examined were recorded with delays of ≤30 days, making NRTVSS possible. The pattern of delays was condition-specific and could be used to adjust for delays in the NRTVSS analysis. Despite low sensitivity of recording, implementing NRTVSS in CPRD is worthwhile and could be carried out, at least on a trial basis, for events of interest.