Immunization information systems use during a public health emergency in the United States.

Use of the Louisiana Immunization Network for Kids Statewide (LINKS) during the aftermath of Hurricane Katrina saved parents and immunization providers' time- money- and the inconvenience of having to unnecessarily revaccinate children displaced both inside and outside Louisiana. This immunization information system remained online via a backup system following the hurricane- thereby making immunization history data available to queries from healthcare providers caring for displaced persons both within Louisiana and throughout the United States. LINKS contained immunization records for approximately 1.5 million people of all ages at the time of the hurricane. Assessment of more than 21 000 successful electronic immunization queries of children and adolescents displaced outside Louisiana state boundaries from virtually all states estimates that more than \$4.6 million was saved in revaccination expenses. The impact of recovered records for these children within Louisiana is certainly as critical. Our review il