LAUSR

BACKGROUND Effects of universal varicella vaccination on the herpes zoster (HZ) incidence have not been elucidated. Universal varicella vaccination was introduced in Japan in October 2014. OBJECTIVE We investigated the effects of universal varicella vaccination on HZ epidemiology. METHODS Patients with HZ have been monitored by the Miyazaki Dermatologist Society since 1997, and the effects of universal vaccination on the HZ incidences have been analyzed to determine which generation is most affected. RESULTS The number of HZ patients increased 1.54 times, and the gradual increase in the HZ incidence was observed in not only patients >60 years, but also other generations during the period from 1997 to 2017. The number of varicella patients was gradually reduced from 2010 to 2017 before introduction of universal varicella vaccination, and the HZ incidence in yearly change significantly increased from 2014 to 2016 in the total population associated with the significant decrease in varicella incidence. The HZ incidence significantly increased for individuals aged 20 to 49 years from 2014 to 2015 and most for individuals age 20-29 years (odds ratio [OR], 1.270; 95% confidence interval [CI], 1.071-1.505, P<0.001). We identified the child-rearing generation of age 20 to 49 years (OR, 1.270; 95% CI, 1.071-1.505, P<0.001) as the generation most influenced by universal varicella vaccination, when the HZ incidence increased gradually by approximately 2% per year. CONCLUSIONS Universal vaccination increased the HZ incidence in the child-rearing generation among the generations, possibly by reduced chance of boosting their immunity by exposure to varicella.