Safety of live attenuated herpes zoster vaccine in adults 70-79 years: A self-controlled case series analysis using primary care data from Australia’s MedicineInsight program

Background: Australia introduced a funded shingles vaccination program for older adults in November 2016, administered predominantly in primary care clinics. MedicineInsight, a nationally representative primary care database, was used to investigate the risk of pre-specified outcomes following live attenuated herpes zoster vaccine (ZVL) in Australia.
Methods: Individuals aged 70-79 years who received ZVL between 1 November 2016 and 31 July 2018 were identified from MedicineInsight. The self-controlled case series (SCCS) method was used to estimate the seasonally-adjusted relative incidence (RI) of seven pre-specified outcome events (injection site reaction (ISR) [positive control], burn [negative control], myocardial infarction (MI), stroke, rash, rash with an antiviral prescription, and clinical attendance) during a plausible post-vaccination at-risk window compared with times distant from vaccination. Sensitivity analyses examined the effect of common concomitant vaccinations and restriction to first outcome events.
Results: A total of 332,988 vaccination encounters among 150,054 individuals were identified during the study period; over 2 million clinical attendances were observed. There was an increased RI of ISR in the seven days following ZVL (RI = 77.4, 95% CI 48.1-124.6); the RI of clinical attendance (RI = 0.94, 95% CI 0.94-0.95) and stroke (RI = 0.58, 95% CI 0.44-0.78) were lower in the 42 days following administration of ZVL compared to control periods. There was no evidence of a change in the RI of MI (RI = 0.74, 95% CI 0.41-1.33), rash (RI = 0.97, 95% CI 0.88-1.08), or rash with antiviral prescription (RI = 0.83, 95% CI 0.62-1.10) in the 42 days following ZVL compared to control periods.
Conclusion: No new safety concerns were identified for ZVL in this study based on a novel, Australian primary care data source. An expected increased risk of ISR was identified; findings in relation to cardiovascular disease were reassuring but require confirmation using additional data, including hospital records.