Abstract 1022

With the recent licensure of a rotavirus vaccine for infants, it is important to have measures in place to monitor the impact of the vaccine on moderate to severe gastroenteritis. We examined gastroenteritis encounters in three settings to assess the usefulness of these data as proxy measures for rotavirus disease. We used hospital admission and emergency department visit data from 1990-1997 and <24 hour short-stay admission data from 1994-1997 at Children's Hospital Medical Center, which serves >97% of children <5 years of age in Hamilton County. Using ICD-9-CM discharge codes for gastroenteritis for Hamilton County children 1 month-5 years of age and US Census data for the same group, we found an average of 254 hospital and short-stay admissions per year and 2378 emergency department visits per year. Gastroenteritis accounted for 6.9% of all hospital and short-stay admissions and 7.4% of all emergency department visits. Short-stay admissions accounted for 26.3% of all gastroenteritis admissions from 1994-1997. The crude annual rate of gastroenteritis for hospital and short-stay admissions was 38/10,000 and 359/10,000 for emergency department visits. Overall during the first 5 years of life, 1 in 52 children from Hamilton County was hospitalized and 1 in 6 required an emergency department visit for gastroenteritis. There was no trend by year. An April-May seasonal trend for gastroenteritis was present for each year, for all age groups and for each encounter site (hospital admissions, short-stay admissions and emergency department visits). The rotavirus-specific ICD-9-CM code (introduced in 1992) was not used until 1995, was rarely used for hospital and short-stay admissions (85 cases) and was never used in the emergency department. We found emergency department estimates to be higher than those previously reported, found a change in hospital admission trends with the use of short-stay admissions and found minimal use of rotavirus testing and rotavirus-specific ICD-9-CM coding. These limitations in the passive surveillance mechanisms for rotavirus gastroenteritis demonstrate a need to actively monitor gastroenteritis encounters in defined populations in children in these three settings to determine the true burden of rotavirus disease, to develop methods to validate the passive surveillance system and to assess the effectiveness of the rotavirus vaccine post-licensure.