Hospitalizations for varicella have declined 88% since 1994–1995, with the biggest decrease seen among infants.
Because infants are not eligible to receive the vaccine, “The decline reflects reduced force of varicella infection in the population (i.e., herd immunity),” as do declining rates among adults and adolescents, reported Dr. Fangjun Zhou, Ph.D., and associates (JAMA 2005;295:797–802).
Dr. Zhou, of the Centers for Disease Control and Prevention, examined varicella treatment codes extracted from a national health plan database of 4 million consumers, from 1994–2002. He found an overall decline in varicella hospitalization, from 2.3/100,000 to 0.3/100,000 (88%).
Hospitalization rates declined for every age group: 100% for infants; 91% for children aged 9 years and younger; 92% for children aged 10–19 years; and 78% for adults aged 20–49 years. Ambulatory visits for varicella also fell sharply, declining 59% over the period.
National spending on varicella hospitalizations and ambulatory visits fell from $85 million in 1994–1995 to $22 million in 2002.