BACKGROUND

Immunocompromised adults are at increased risk of herpes zoster (HZ) infection and related complications. We aimed to assess the incidence of hospital-attended HZ (i.e., seen in hospital or emergency department [ED]) in immunocompromised populations and compare it to immunocompetent populations.

METHODS

We calculated incidence rates (IR) of hospital-attended HZ in Ontario, Canada between April 1, 2002 and August 31, 2016 in adults ≥18 years categorized as immunocompromised or immunocompetent. We repeated these analyses by type of immunocompromising condition and provided incidence rate ratios (IRR) comparing to immunocompetent adults. We also calculated IRs and IRRs of HZ complications by immunocompromised status.

RESULTS

There were 135,206 incident cases of hospital-attended HZ during the study period. Immunocompromised adults accounted for 13% of these cases despite representing 3% of the population. The risk of hospital-attended HZ was higher for immunocompromised adults compared with immunocompetent (IRR=2.9, 95% CI 2.9-3.0) and ranged across type of immunocompromising condition, from 2.6 (95%CI 2.6-2.7) in those with a solid tumour malignancy to 12.3 (95%CI 11.3-13.2) in those who had undergone a hematopoietic stem cell transplant. The risk of any HZ complication was higher in immunocompromised adults (IRR=3.6, 95%CI 3.5-3.7) and highest for disseminated zoster (IRR=32.8, 95%CI 27.8-38.6).

CONCLUSIONS

The risk of hospital-attended HZ and related complications was higher in immunocompromised populations compared with immunocompetent. Our findings underscore the high-risk nature of this population and the potential benefits that may be realized through HZ vaccination.