Decline in Mortality Due to Varicella after Implementation of Varicella Vaccination in the United States. Nguyen HQ, Jumaan AO, and Seward JF. New England Journal of Medicine, 2005;352(5):450-458.
What has been the effect of vaccination against chickenpox on the number of deaths due to chickenpox in the United States?
Researchers analyzed data on deaths in the US due to chickenpox from the National Center for Health Statistics Multiple Cause of Death Mortality Data for 1990 through 2001. The study also examined whether the chickenpox infection was the cause of death or contributed to the cause of death—for example, the cause of death was because of a bacterial infection of chickenpox lesions.
The number of deaths due to chickenpox was also calculated according to age, sex, race, ethnic background and birthplace. Preexisting conditions that increased the likelihood of severe chickenpox infection, complications of the disease and seasonal trends were also examined in this study.
This study found that from 1990 through 2001, 1,465 death records listed chickenpox as the cause or a contributing cause of death. Chickenpox-related deaths averaged 145 per year from 1990 through 1994 (before the vaccine was licensed) and declined to 66 per year from 1999 through 2001 (when the vaccine was being used).
The decline in deaths due to chickenpox was noted in all age groups less than 50 years of age, but especially in children 1 to 4 years of age. Additionally, since vaccine introduction, racial and ethnic disparities in chickenpox mortality disappeared.
The decline in the number of deaths due to chickenpox has coincided with the increased use of chickenpox vaccine in the United States.
Universal childhood immunization with chickenpox vaccine was recommended in 1995, but the proportion of children who had received varicella vaccine was estimated by CDC to be only 26% in 1997 rising to 76% in 2001. As a consequence, the reported decline in chickenpox mortality occurred despite low immunization levels in much of the study time period.