Summary: The Vaccine Injury Compensation Program pays medical and other expenses for people who have been harmed because of adverse reactions to vaccinations against such diseases as measles and polio. People seeking compensation for vaccine injuries must file a claim with the program, instead of suing the vaccine manufacturer. GAO found that two vaccines (one for whooping cough and the other for polio), which account for 88 percent of the trust fund payments for injury claims through 1999, are being phased out of use in the United States. Vaccines against four diseases have been added to the program since 1997, but, as of December 1999, only six of the 285 claims filed related to these vaccines had been adjudicated, and only one $600 payment for attorney fees had been made from the trust fund. For the remaining claims, program officials were either waiting for petitioners to submit missing information or were still processing them. Current annual appropriations to reimburse agencies from the trust fund for administrative expenses--about $9.6 million--appear to be enough to meet agency needs. The $1.46 billion trust fund balance appears to be more than adequate, given the experience so far for claims payments and related administrative costs.