The burden of herpes zoster disease in Norway.

BACKGROUND:No national vaccination program against herpes zoster (HZ) is currently in place in Norway. We aimed to quantify the burden of medically attended HZ to assess the need for a vaccination program. METHODS:We linked data from several health registries to identify medically attended HZ cases during 2008-2014 and HZ-associated deaths during1996-2012 in the entire population of Norway. We calculated HZ incidences for primary and hospital care by age, sex, type of health encounter, vaccination status, and co-morbidities among hospital patients. We also estimated HZ-associated mortality and case-fatality. RESULTS:The study included 82,064 HZ patients, of whom none were reported as vaccinated against HZ. The crude annual incidence of HZ was 227.1 cases per 100,000 in primary healthcare and 24.8 cases per 100,000 in hospitals. Incidence rates were higher in adults aged ≥50 years (461 per 100,000 in primary care and 57 per 100,000 in hospitals), and women than in men both in primary healthcare (267 vs 188 per 100,000), and hospitals (28 vs 22 per 100,000). Among hospital patients, 47% had complicated zoster and 25% had comorbidities, according to the Charlson comorbidity index. The duration of hospital stay (median 4 days) increased with the severity of comorbidities. The estimated mortality rate was 0.18 per 100,000; and in-hospital case-fatality rate was 1.04%. CONCLUSIONS:Medically attended HZ poses a substantial burden in the Norwegian healthcare sector. The majority of the zoster cases occurred among adults aged ≥50 years - the group eligible for zoster vaccination - and increased use of zoster vaccination may be warranted, especially among persons with co-morbidities.