title: Varicella vaccination alters the chronological trends of herpes zoster and varicella.
abstract: BACKGROUND
  Population studies on trends of varicella and herpes zoster (HZ) associated with varicella zoster vaccination and climate is limited.
  
  
  METHODS
  This study used insurance claims data to investigate the chronological changes in incident varicella and HZ associated with varicella zoster vaccination. Poisson regression was used to estimate the occurrence of varicella associated with the occurrence of HZ and vice versa by year, season, sex, temperature, and sunny hours.
  
  
  RESULTS
  The varicella incidence declined from 7.14 to 0.76 per 1,000 person-years in 2000-2009, whereas the HZ incidence increased from 4.04 to 6.24 per 1,000 person-years. Females tended to have a higher risk than men for HZ (p<0.0001) but not varicella. The monthly mean varicella incidence was the lowest in September (160 cases) and the highest in January (425 cases), while the mean HZ incidence was lower in February (370 cases) and higher in August (470 cases). HZ was negatively associated with the incidence of varicella before and after the varicella zoster vaccination (p<0.001), increased 1.6% within one week post-vaccination. The effect of temperature on HZ was attenuated by 18.5% (p<0.0001) in association with vaccination. The varicella risk was positively associated with sun exposure hours, but negatively associated with temperature only before vaccination.
  
  
  CONCLUSIONS
  The varicella vaccination is effective in varicella prevention, but the incidence of HZ increases after vaccination. HZ has a stronger association with temperature and UV than with seasonality while varicella risk associated with temperature and UV is diminished.
authors.affiliation: Department of Public Health, China Medical University, Taichung, Taiwan ; Department of Dermatology, China Medical University Hospital, Taichung, Taiwan ; School of Medicine, China Medical University, Taichung, Taiwan.
authors.forename: Po-Yuan
authors.initials: PY
authors.lastname: Wu
authors.forename: Hong-Dar Isaac
authors.initials: HD
authors.lastname: Wu
authors.forename: Tzu-Chieh
authors.initials: TC
authors.lastname: Chou
authors.forename: Fung-Chang
authors.initials: FC
authors.lastname: Sung
mesh_terms: D002644:Chickenpox / Q000453:epidemiology* / Q000276:immunology* / Q000517:prevention & control; D005260:Female; D006562:Herpes Zoster / Q000453:epidemiology* / Q000276:immunology* / Q000517:prevention & control; D006801:Humans; D015994:Incidence; D008297:Male; D012307:Risk Factors; D012621:Seasons; D016082:Solar System; D013696:Temperature; D014466:Ultraviolet Rays; D014611:Vaccination