COMPLETENESS OF REPORTING FOR PARALYTIC POLIOMYELITIS, UNITED-STATES,1980 THROUGH 1991 - IMPLICATIONS FOR ESTIMATING THE RISK OF VACCINE-ASSOCIATED DISEASE

Background: Although the risk of vaccine-associated paralytic poliomye litis (VAPP) has remained relatively constant during the past 30 years , estimates of VAPP depend largely on the completeness of reporting to the existing passive surveillance system. The National Vaccine Injury Compensation Program constitutes an alternative system for reporting VAPP, and data available from this system permitted us to evaluate the completeness of the national poliomyelitis surveillance system. Metho ds: We compared cases of paralytic poliomyelitis reported to the natio nal surveillance system (maintained by the Centers for Disease Control and Prevention, Atlanta, Ga) with cases recommended for compensation by the National Vaccine Injury Compensation Program, Rockville, Md, an d we calculated the observed completeness of reporting to the national system for 1980 through 1991. A capture-recapture method was also use d to estimate completeness of reporting, ie, to account for cases pote ntially missed by both systems. In addition, we reviewed the epidemiol ogy and updated the risk of VAPP based on the most current information on cases of VAPP. Results: From 1980 through 1991, 105 cases of paral ytic poliomyelitis were identified by the Centers for Disease Control and Prevention and National Vaccine Injury Compensation Program system s, 98 (93%) of which were VAPP (average, 8.2 cases per year). The obse rved completeness of reporting to the Centers for Disease Control and Prevention was 94%, and the estimated completeness of reporting (captu re-recapture method) was 81%. The overall risk of VAPP was one case pe r 2.5 million doses of oral poliovirus vaccine distributed. In the sen sitivity analysis, the risk estimates of VAPP remained relatively stab le throughout a wide range of assumptions regarding underreporting and specificity of the case definition for paralytic poliomyelitis. Concl usion: The risk of VAPP remains virtually unchanged from previous esti mates despite the inclusion of previously unidentified VAPP cases. Des pite the potential for both underreporting and misclassification of ca ses, our risk estimates were relatively insensitive to either of these biases. Since both of these biases were in opposite directions, and b oth probably occurred with low frequency, the risk estimates provided in this report appear valid and approximate the ''true'' risk of VAPP in the United States.