Background: It is well known that immunosuppressed status such as cancer is a risk factor for herpes zoster (HZ), but little is known about whether HZ affects cancer development. 
Methods: This study aimed to investigate the association between HZ and the subsequent cancer risk. We conducted a nationwide retrospective cohort study using the Korean National Health Insurance claims database between 2010 and 2015. 
Results: In total, 784,409 HZ group and 784,409 controls without HZ after 1:1 exact matching for age, sex, and index year were included in the study. Overall, 22,235 and 22,316 patients in the HZ and non-HZ cohorts, respectively, developed cancer (incidence rate: 7.6 vs. 7.7 per 1000 person-years). After adjusting for age, sex, and comorbidities, the HZ cohort had significantly increased risks of hematologic malignancies, including multiple myeloma (HR 1.63, 95% CI 1.37–1.95), leukemia (HR 1.20, 95% CI 1.03–1.39), and lymphoma (HR 1.15, 95% CI 1.02–1.30) compared with the non-HZ cohort. Conversely, the risks of cancers in the liver (HR 0.87, 95% CI 0.82–0.93) and larynx (HR 0.73, 95% CI 0.58–0.92) were significantly decreased in HZ cohort compared with the non-HZ cohort.
Conclusion: Our data showed that HZ had a significant association with the development of hematologic malignancies but did not increase the risk of other cancers.

Herpes Zoster and Risk of Cancer: A Nationwide Population-Based Cohort Study