The epidemiology of herpes zoster (HZ), particularly in the unvaccinated immunocompetent population, was the subject of a recent study. The report in the Journal of Infectious Diseases said the review was needed to assess disease burden and the potential effect of vaccination. It determined that age made a difference, with the oldest-old having the worst effects.

The study, which was conducted at Kaiser Permanente Southern California, a large, integrated healthcare organization, involved five elements:

• Incidence estimated from immunocompetent adults aged ≥50 years who were unvaccinated with zoster vaccine live and who had incident HZ in 2011-2015; 
• The proportion of HZ-related complications—not including pain—assessed by double abstraction of electronic health records of 600 incident patients from 2011 to 2015; 
• HZ-related hospitalizations identified among patients diagnosed in 2015;
• HZ-related deaths determined from automated data and review of electronic health records; 
• Recurrent HZ identified from a cohort initially diagnosed with HZ in 2007-2008 and followed through 2016.

Results indicate that the HZ incidence rate was 9.92/1,000 person-years (95% confidence interval [CI], 9.82%-10.01%). 

Researchers report that the proportion of cutaneous, neurologic, and other complications was 6.40% (95% CI,1.73%-11.07%), 0.77% (95% CI, 0.00%-2.36%), and 1.01% (95% CI, 0.00%-2.93%), respectively. 

Relatively few, only 0.86%, of the patients had to be hospitalized because of HZ, and the  case-fatality rate was 0.04%. The study determined that the recurrence rate was 10.96/1,000 person-years (95% CI, 10.18%-11.79%), with a 10-year recurrence risk of 10.26% (95% CI, 9.36%-11.23%).

“Data included in this study were obtained prior to RZV approval, and therefore provide timely updates to better assess the potential impact of the uptake of RZV on HZ epidemiology,” the authors point out. “Our results also provide estimations for parameters that are needed in cost-effectiveness and budget impact analyses to help inform policy decisions.”

Researchers explain that the study provides important estimations for base case values in an immunocompetent population that are necessary for vaccine economic model analyses, adding, “Our data suggest that HZ-related mortality is infrequent in immunocompetent HZ patients. Mortality and hospitalization mainly occur in the oldest-old. The incidence rate and recurrence rate had different trends with increased age.”

The authors note that the linear increase of recurrence over time does not support the hypothesis of HZ preventing recurrence. “Although utilization data may be affected by health-seeking behavior or accessibility to care, they directly reflect the real-world disease burden to healthcare systems,” they conclude.

« Click here to return to Vaccine Update.