BACKGROUND:
Varicella has been a reportable condition in Texas since 1972 first by number of cases, then by age-grouped summaries, and finally in 2001 by named reporting. Although the number of cases reported has been about 6% of the birth cohort, a pre-vaccine estimator of expected incidence, the level of reporting has been very stable making it possible to monitor trends in varicella incidence. Varicella vaccine was licensed in 1995 and the Advisory Committee on Immunization Practices (ACIP) recommended routine vaccination of all children at age 12-18 months and catch-up vaccination of all susceptible children by 13 years-of-age. In 1999 the Texas Board of Health added varicella vaccination to the requirements for children attending day-care facilities and those starting school or turning 12 years-of-age.

OBJECTIVE:
Assess the impact of vaccination and school requirements on the incidence of varicella in Texas using statewide surveillance data.

METHOD:
Texas surveillance data was reviewed to ascertain the level of reporting from 1990 through 2002 using both the percentage of the birth cohort and the number of counties reporting activity. The statewide incidence was calculated for reported cases each year since 1990 to assess the trends in varicella incidence and the impact of vaccination and school requirements.

RESULT:
Beginning in 1999, Texas reported a marked decline in the incidence of reported varicella. This occurred despite a campaign to enhance varicella reporting in 1996 through 1998 and the initiation of named reporting in 2001. The number of counties reporting activity increased from about 45% in the early 90s to greater than 50% since 1995 and greater than 60 % since 2001.

CONCLUSION:
Despite stable or increasing surveillance, incidence of varicella declined sharply in 1999 and again in 2001.

LEARNING OBJECTIVES:
To demonstrate the impact of varicella vaccination and school requirements on the incidence of varicella.