Incidence and Burden of Herpes Zoster in Sweden: A Regional Population-Based Register Study.

ABSTRACT

INTRODUCTION: Herpes zoster (HZ) is a painful disease that mainly affects individuals whose immune system has been weakened because of increasing age (> 50 years) or certain diseases or treatments. We estimated the complete burden of HZ. METHODS: This population-based register study analysed healthcare data from the VEGA and Digitalis databases of Västra Götaland Region (VGR), Sweden. The VEGA database includes all patients in VGR, covering both hospital and primary care. The Digitalis records prescribed medications. The study population included patients aged ≥ 18 years with at least one registered primary or secondary HZ diagnosis (based on International Classification of Diseases [ICD] codes) between 2005 and 2021. Incidence rates (95% confidence intervals [CI]) were stratified by age, sex and diagnosis/analgesic prescription. RESULTS: Overall HZ incidence increased from 2.5 (95% CI 2.4-2.6) in 2005 to 4.2 (95% CI 4.1-4.3) in 2021. The increase in incidence was rapid from 2005 to 2013, followed by a plateauing trend. From 2014-2019, the lifetime risk of HZ, excluding recurrent cases, was 36.5% (95% CI 35.5-37.4%). Municipal differences ranged from 34.4% (95% CI 32.5-36.4%) to 43.6% (95% CI 39.9-47.4%). Recurrence rates of HZ were 8.7% and 9.1% with follow-up periods of 5.5 and 10.5 years, respectively. Reported postherpetic neuralgia (PHN) cases increased five-fold over the study period. In 2019, 19% of all HZ patients developed HZ-related neuropathic pain; 13.6% had signs of persistent pain (> 90 days; i.e. PHN). An increased occurrence of cerebral and cardiovascular disease was observed in HZ patients. Among high-risk groups the occurrence of HZ peaked among those with inflammatory and autoimmune diseases. CONCLUSION: HZ and PHN risk in Sweden is comparable to that in other European countries prior to implementing HZ national vaccination programs. Municipal differences suggest that the lifetime risk of HZ in Sweden is at least 36.5%. CLINICAL TRIAL REGISTRATION NCT Number ( www. CLINICALTRIALS gov ).

What is the context?The varicella-zoster virus (VZV) can reactivate after primary infection and cause herpes zoster or shingles.Shingles is painful and mostly affects people aged > 50 years or those who have weakened immunity due to age, illness or medical treatments.The National Immunization Program (NIP) in Sweden does not currently include vaccination against shingles.We evaluated how often individuals from Västra Götaland Region, Sweden, experienced shingles and its complications.What is new?Overall, the number of shingles and PHN cases increased significantly from 2005 to 2021.We found that 14% of patients with shingles had pain persisting for > 3 months after a shingles episode.Most people developing shingles (about 70%) are healthy individuals without comorbidities, although those with underlying health issues have more risk of getting shingles.Over a follow-up period of 5.5 years, 8.7% of patients with shingles had more than one shingles episode.What is the impact?The occurrence of shingles and postherpetic neuralgia in Sweden is higher than what was reported previously and is comparable to other European countries before the implementation of shingles vaccination programmes.