Varicella-related mortality in California, 1988-2000.

BACKGROUND

Although surveillance for varicella in the United States has documented a reduction in cases since vaccine licensure in 1995, information is lacking on varicella-related mortality since vaccine introduction. This study identifies varicella-related mortality in California before and after vaccine introduction and assesses how high risk conditions and complications contributed to varicella deaths during this period.

METHODS

California death records mentioning varicella as either an underlying or contributing cause of death were selected from the 1988-2000 multiple cause-of-death files. Pre- and postvaccine periods were compared to assess differences in varicella mortality before and after vaccine introduction. Differences in varicella mortality by age, race/ethnicity and gender were also examined. ICD codes were used to identify high risk conditions and varicella-related complications.

RESULTS

A total of 228 varicella-related deaths were reported between 1988 and 2000 in California. Age-adjusted varicella mortality rates showed a downward trend during this period, dropping from a high of 0.97 per million in 1990 to a low of 0.22 per million in 1999. The average age-adjusted mortality rate declined from 0.67 per million prevaccine to 0.38 per million postvaccine. Compared with the prevaccine period, the average rate of decline in varicella mortality was greater after vaccine implementation. Infants had the highest mortality rate for the period. At least one immunocompromising condition was present in 38% of varicella-related deaths. Pneumonia was the most commonly reported complication.

CONCLUSIONS

Varicella-related mortality declined in California after vaccine implementation, but potentially preventable varicella-related deaths continue to occur.