Reactivation of the varicella zoster virus later in life is known as herpes zoster (HZ) infection or shingles. Recent studies have shown increasing incidence of HZ infection, which maybe related to the introduction of the varicella vaccination program in children. We looked at the epidemiology of HZ and its complications, including post-herpetic neuralgia (PHN) over time.
The cohort, obtained from PopulationDataBC, was all cases with HZ infection from January 1, 1997 and December 31, 2012. Incident zoster was defined as a case with an ICD-9 code of 053 or ICD-10 code of B02 without a previous episode of HZ or PHN in the previous 12 months. PHN was identified as those with a first episode of HZ with a further zoster diagnostic code after 90 d with a relevant prescription for analgesia, anticonvulsant, or antidepressant therapy on the same day as the recorded consultation. Age-sex standardized rate for the overall population was calculated using the 2006 Canadian census. Incidence for HZ and PHN was determined by identifying the number of events per 1000 population. We determined the association between the varicella vaccination program and increased HZ rates by evaluating the rate ratios in the publicly-funded varicella vaccine period compared to the pre-licensure and privately-available periods and through a regression model.
HZ incidence increased for the entire study period from 3.2 per 1000 population in 1997 to 4.5 in 2012. HZ rates were higher for females than males and for all age groups, except the 0-9 year olds, where the rate decreased. All regions of British Columbia followed the same pattern and increase. Crude and age-sex standardized incidence rate of PHN demonstrated very similar patterns of HZ incidence. Based on the regression model, rates of HZ were higher in the older individuals, females, and those who were immunocompromised. We will explore if an increase with HZ incidence is seen during the publically funded varicella vaccination program compared to the pre-licensure and privately funded periods.
The incidence of zoster and PHN is increasing with time, particularly in the elderly population and the risk is greater in over 65 years, females and those immunocompromised.
Merck Canada Inc:
M. Najafzadeh, None