P’s daughter was given a DPT vaccine. The child's mother noticed that within twenty-four hours of the inoculation Deanna displayed symptoms of extreme pain. The rapid deterioration of her condition resulted in the loss of her then-acquired verbal, motor, and mental capacities. Deanna, now eighteen years of age, has been diagnosed as having chronic encephalopathy and severe retardation. She is institutionalized and requires constant care. P was unable to identify the manufacturer of the particular vaccine dose and sued all manufacturers of the vaccine. The trial court granted summary judgment in favor of Ds. On appeal, the court reversed, and eliminated the requirement of proof of causation, and substituted 'risk-modified market share' liability, shifting the burden to defendants to demonstrate they had not produced the vaccine. D appealed.