Secular trends in the epidemiology of shingles in Alberta

Varicella vaccine was licensed in Canada in 1998, and a publicly funded vaccination programme introduced in the province of Alberta in 2001. In theory the vaccination programme might increase the burden of disease from shingles, making it important to develop baseline data against which future comparisons can be made. The study's aim was to describe the epidemiology of non-fatal cases of shingles for which publicly funded health services were utilized for the period 1986-2002. Shingles cases were identified from the records of Alberta's universal, publicly funded health-care insurance system for 1986-2002. The earliest dated health service utilizations for ICD-9-CM codes of 053 or ICD- 10-CA codes of B02 were classified as incident. Diagnostic codes at least 180 days after the first were classified as recurrent episodes. Denominators for rates were estimated using mid-year population estimates from the Alberta Health Care Insurance Plan Registry. Annual age- and sex-specific rates were estimated. We explored the pattern of rates for sex, age and year effects and their interactions. Shingles rates increased between 1986 and 2002. There was a sex effect and evidence of an age-sex interaction. Females had higher rates than males at every age; however, the difference between females and males was greatest for the 50-54 years age group and declined for older age groups. The increased rate of shingles in Alberta began before varicella vaccine was licensed or publicly funded in Alberta, and thus cannot be attributed to vaccination.