Herpes Zoster and Exposure to the Varicella Zoster Virus in an Era of Varicella Vaccination

摘要

Objectives. We performed a case–control study to determine if participants with herpes zoster had fewer contacts with persons with varicella or zoster, and with young children, to explore the hypothesis that exposure to persons with varicella zoster virus (VZV) results in “immune boosting.” Methods. Participants were patients of the multispecialty Marshfield Clinic in Wisconsin. We identified patients aged 40 to 79 years with a new diagnosis of zoster from August 2000 to July 2005. We frequency matched control participants to case participants for age. We confirmed diagnoses by chart review and assessed exposures by interview. Results. Interviews were completed by 633 of 902 eligible case participants (70.2%) and 655 of 1149 control participants (57.0%). The number of varicella contacts was not associated with zoster; there was no trend even at the highest exposure level (3 or more contacts). Similarly, there was no association with exposure to persons with zoster or to children, or with workplace exposures. Conclusions. Although exposure to VZV in our study was relatively low, the absence of a relationship with zoster reflects the uncertain influence of varicella circulation on zoster epidemiology. Herpes zoster, also known as shingles, is a condition caused by reactivation of the latent varicella zoster virus (VZV), which lies dormant in sensory ganglia after primary infection (i.e., chickenpox). 1 Clinically, the condition is usually characterized by a painful vesicular rash in a dermatomal pattern. A summary of several investigations estimates the annual number of zoster cases at 1 million after age adjustment to the 2000 US population. 2 Although the factors that allow virus reactivation in healthy individuals are not completely understood, it is believed that a decline in cell-mediated immunity plays a pivotal role. 3 , 4 Since licensure of the varicella vaccine in 1995, there has been a dramatic decline in the number of chickenpox cases in the United States. 5 However, there is concern that the relative absence of VZV circulating in the population may result in reduced immune boosting and an increase in the incidence of zoster. 6 , 7 Evidence to support this hypothesis was provided by a case–control study in the United Kingdom that found that contacts in the previous 10 years with varicella and with children reduced the risk of zoster. 8 We describe a case–control study to test the hypothesis that persons with zoster have fewer contacts with persons with varicella or zoster, and fewer contacts with young children, compared with persons without zoster. The latter exposure is included because varicella is infectious before onset of the rash, 9 and because some varicella probably occurs among vaccinated children. These breakthrough cases are relatively mild and the diagnosis may be delayed or missed entirely. 10 , 11 .