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BACKGROUND: The 1-dose varicella vaccination program was introduced in the U.S. in 1996 and a routine 2-dose vaccination program was adopted in 2007. We previously reported changes in varicella health-care utilization during 1994-2002 with an 88% decline in varicella-related hospitalizations and 59% decline in outpatient visits between 1994 to 2002. We now update data on varicella health care utilization with 10 years of additional data, during a period of high, stable levels of first-dose coverage and rapidly-increasing levels of second-dose coverage. We examined the impact of the varicella vaccination program on outpatient visits and hospital admissions during 1994-2012.
METHODS: We conducted a retrospective cohort study using claims data from 1994-2012 Truven Health MarketScan® databases to examine varicella health care utilization for enrollees aged 0-49 years. We examined trends in rates of varicella-related outpatient visits and hospitalizations, with 1994-1995 as the pre-vaccination baseline data and 2006-2012 as the 2-dose varicella vaccination period.
RESULTS: Between the pre-vaccination era (1994-1995) and 2012, varicella outpatient visits declined from an average rate of 215 per 100,000 to 33 per 100,000 (84% decline) and hospitalizations declined from an average rate of 2.35 per 100,000 to 0.16 per 100,000 (93% decline). Between 2006 and 2012 (the 2-dose varicella vaccination era), outpatient visits and hospitalizations declined 60% (from 84 per 100,000 to 33 per 100,000) and 38% (from 0.27 per 100,000 to 0.16 per 100,000), respectively. Outpatient visits and hospitalizations declined by 95% and 99%, respectively, among infants aged <1 year-old between the pre-vaccination era and 2012.
CONCLUSIONS: While varicella vaccination led to substantial declines in varicella morbidity during the first decade of the program, additional significant declines in morbidity have occurred since the implementation of the 2-dose varicella vaccination program.