Herpes Zoster (HZ) complications can cause considerable morbidity including debilitating pain syndromes. Clinical trials of tofacitinib have suggested it may increase the risk of HZ. Although unclear, the mechanism may involve reduced CD4 T-cell function and interference of interferon signalling. Following approval of tofacitinib in the US in 2012, real-world data from Medicare (2006–2013) and from the US longitudinal database, Marketscan, (2010–2014) were analysed. A total of 2526 patients who...