Jane F. Seward, M.B.B.S., M.P.H., from the Centers for Disease Control and Prevention (CDC), and colleagues studied trends in the number and rate of varicella cases and hospitalizations and vaccine coverage in the populations of Antelope Valley, Calif.; Travis County, Tex.; and West Philadelphia, Pa., from January 1, 1995, to December 31, 2000.

(The varicella, or chickenpox vaccine was first introduced in 1995.)

"Four years after implementation of the varicella vaccination program in the United States, data from active surveillance areas showed dramatic evidence of vaccine impact with a marked decline in reported cases in all age groups," the authors report.

"From 1995 through 2000, in Antelope Valley, Travis County, and West Philadelphia," they continue, "varicella cases declined 71 percent, 84 percent, and 79 percent, respectively. The decline in disease was greatest in preschool children; however, declines occurred in every age group including infants and adults, indicating reduced transmission of varicella zoster virus in these communities."

Before introduction of the varicella vaccine in 1995, chickenpox was a universal childhood disease in the U.S., causing 4 million cases and 11,000 hospitalizations and 100 deaths annually.

The authors note that since varicella is not a nationally reportable disease in the U.S., national surveillance data were not available to monitor the impact of the varicella vaccination program.

However, in 1995, the Centers for Disease Control and Prevention, in collaboration with state and local health departments, instituted active surveillance in the three communities cited in the study.

Antelope Valley is a health services district of the Los Angeles County Department of Health Services; Travis County is the most densely populated county in central Texas, and West Philadelphia is an inner-city area of Philadelphia.

In those jurisdictions, schools, universities, child care centers and preschools, private health care providers, health maintenance organizations, emergency departments, hospitals, public health clinics and other sources reported varicella cases to the project offices.

In all locations, the number of varicella cases declined in 1996, remaining fairly stable until 1999, when a marked decline occurred.

Between 1995 and 2000, the number of cases in Antelope County declined from 2,934 to 837; in Travis County, from 3,130 to 491 cases; and in West Philadelphia, from 1,197 to 250 cases.

The authors conclude, "Continued active surveillance for varicella in these surveillance areas and establishing and enhancing passive varicella surveillance systems at the state level with attention focused on monitoring vaccine coverage among adolescents as well as young children will be important to ensure that coverage continues to increase to the high levels that will be required for sustained reduction of varicella U.S. morbidity."

(Reference: JAMA. 2002;287:606-611.)

06-Feb-2002