Since the universal childhood varicella vaccination program was implemented in the United States in 1995, there has been a sharp decline in chickenpox-related deaths, according to researchers from the Centers for Disease Control and Prevention (CDC).

Initial infection with the varicella-zoster virus results in chickenpox, which primarily affects children, but can also occur in adults. Reactivation of the virus, which primarily occurs in older or immunocompromised adults, causes shingles.

Previous reports have documented a drop in chickenpox cases after the program was in place, but the effect on death rates was unclear. Although this endpoint has been investigated, previous studies have only included cases in which varicella infection was listed as the underlying cause, not as a contributing cause.

In the present study, Jane F. Seward and colleagues, from the Atlanta-based CDC, analyzed mortality data collected between 1990 and 2001 to gauge the impact that the vaccine program had on varicella-related deaths. Cases listing varicella infection as either an underlying or contributing cause were included in the analysis.

After fluctuating between 1990 and 1998, the varicella-related death rate dropped sharply, the authors report in The New England Journal of Medicine. From 1990 to 1994, the average number of varicella-related deaths per year was 145. In contrast, between 1999 and 2001, this figure was just 66.

Considering only cases listing varicella infection as an underlying cause of death, the 11-year study period saw a drop in mortality rates of 66 percent. This decline was observed in all age groups under 50 years and was most pronounced in children between 1 and 4 years of age.

The vaccine program also seemed to reduce racial disparities in chickenpox deaths. Before the program was implemented, the mortality rate was 0.37 per 1 million among whites, but 0.66 per 1 million for other races. After implementation, the rate fell below 0.15 per 1 million for all racial groups.

The currently available data support the success of the U.S. varicella vaccination program and should be useful for countries that are considering a universal varicella vaccination program to reduce varicella-related illness and death, the authors note.

SOURCE: The New England Journal of Medicine, February 3, 2005.