The incidence of herpes zoster (HZ) in the U.S. has been estimated to be 1 million cases or more annually with a higher rate in adults over 60 years of age. Previously, we reported that the incidence of HZ had increased from 3.10 episodes per 1000 veterans in 2000 to 5.22 in 2007. This is a follow-up study to evaluate the incidence of HZ in veterans after the introduction of the zoster vaccine in 2007.
We derived incidence rates using the Veterans Health System Decision Support System (DSS) reports of HZ by ICD-9 code and the corresponding denominator data for all veterans in care. DSS is a national automated management information system that includes clinical and financial data for inpatient and outpatient care. The period of analysis is 2007- 2015. To eliminate duplicate visits for the same episode of HZ, we chose to count only unique patients with HZ code seen each year. The annual rates of HZ were calculated by dividing unique patients with HZ by the total number of veterans seen that year. The same method was used to calculate the rate by age groups. Chi square for trend was calculated for the total and age specific rates over the entire time period. We used data from DSS to present the use of zoster vaccine nationally.
The total number of veterans seen increased from 5,292,175 in 2007 to 6,262,620 in 2015. The number of zoster episodes increased from 28,529 in 2007 to 36,868 in 2015 (Figure.1). Since 2007, the annual incidence of HZ increased slightly from 5.39 per 1000 veterans to 5.89 in 2015 (R2 =0.3273; p=0.1075) (Figure.2). Age-specific rates revealed a drop in the annual incidence of HZ for age groups 40-49 and older after 2013. This drop was only statistically significant for the age group 60-69 (p=0.0153) (Figure.3). There were 239,202 doses of the zoster vaccine administered at the Veterans Affairs (VA) between 2007 and 2015. The estimated coverage for veterans 60 years or older is 6.35% and that for 50 years or older is 5.05%.
The incidence of HZ is stable after years of increase at the VA except for the age group 60-69 where the incidence has been decreasing over the past 2 years. There has been limited use of the zoster vaccine at the VA. Further studies are needed to elucidate the reason behind this trend in the HZ incidence and increased efforts are needed to use the vaccine more widely.
D. Rimland, None