West Philadelphia Varicella Active Surveillance Project
The West Philadelphia Varicella Active Surveillance Project (VASP), a cooperative project funded by the Centers for Disease Control and Prevention (CDC) and implemented by the Philadelphia Department of Public Health, Division of Disease Control (DDC) in October 1994. The primary purpose of the VASP is to monitor and document the epidemiology of varicella-zoster (VZ) viral infection before and after the varicella vaccine became available. Currently the West Philadelphia VASP is one of two sites nationally, along with the Antelope Valley, California, collaborating on the project.
All cases of VZ occurring in the city of Philadelphia are reportable to the Department of Health; however, only cases residing in the West Philadelphia area receive an extensive investigation. Investigations are conducted to confirm diagnosis and establish epidemiological links, as well as to obtain information regarding history of Varicella vaccine, presence of complications, description of illness and spread of disease within households. As part of VASP, data is also collected on varicella-related hospitalizations and deaths, and the occurrence of disease among vaccinated individuals, including those that occur outside of the targeted surveillance area.
Cases of VZ are reported by over 300 participating surveillance sites in the target area, including hospitals, public and private schools, primary care practitioners, public health clinics and large child-care centers. Case identification is facilitated through a standardized surveillance system in which each site receives regular contact to assure that all cases of VZ are being reported. In addition, VZ case logs are used by sites to assist in capturing cases and to standardize the way in which case reports are collected. Hospital billing records are reviewed each month to identify cases which may not have been reported during emergency department or clinic visits.
After notification, each case, or his/her parent/guardian, is interviewed to obtain detailed clinical and demographic information for the reported case. The interviewer assesses whether there are additional cases or susceptible contacts within the household. A case investigation is completed for each newly identified case of VZ. To improve case ascertainment, all susceptible household contacts (individuals who never had natural varicella infection) are re-contacted 3 weeks (1 incubation period) after the onset of the most recent case to investigate potential household spread of varicella infection.
For more information about the VASP Program please call 215-685-6741.
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