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Herpes zoster and postherpetic neuralgia occur more often with increasing age. In this controlled trial among 38,546 adults 60 years of age or older, vaccination with a live attenuated varicella–zoster vaccine reduced the incidence of postherpetic neuralgia by 66.5 percent (as compared with placebo) and the incidence of herpes zoster by 51.3 percent. In adults 60 years of age or older, vaccination with a live attenuated varicella–zoster vaccine reduced the incidence of postherpetic neuralgia by 66.5 percent (as compared with placebo) and the incidence of herpes zoster by 51.3 percent. Herpes zoster, or shingles, is characterized by unilateral radicular pain and a vesicular rash that is generally limited to a single dermatome. 1 , 2 Herpes zoster results from reactivation of latent varicella–zoster virus (VZV) within the sensory ganglia. 3 , 4 The incidence and severity of herpes zoster increase with advancing age; more than half of all persons in whom herpes zoster develops are older than 60 years. Complications occur in almost 50 percent of older persons with herpes zoster. 3 – 5 The most frequent debilitating complication is postherpetic neuralgia, a neuropathic pain syndrome that persists or develops after the dermatomal rash has healed. . . .

Oftentimes participants in randomized trials are clustered at multiple levels. For instance, they may be grouped in practices, which in turn are grouped within hospitals within healthcare systems. The complex hierarchical relationships introduced within resulting data structures must be acknowledged in data analyses to insure valid estimation of treatment effects. When such trials are conducted among older individuals, additional complexities may present themselves, as in the case when death or other competing risks preclude observation of clinical endpoints. When the outcome of interest is a potentially recurrent event, such as fall or hospitalization, there may be interest in understanding the rates of both incidence and recurrence, but existing methods are inadequate to estimate them in this setting. In this presentation, we propose a novel analytic approach for estimation of treatment effects for time-to-event endpoints in the presence of multilevel clustering and competing risks.