He and others emphasized that the deaths occurred among children living in poor countries, many of whom were malnourished and did not have access to adequate health care.
Researchers speculate, but have not been able to prove, that the higher dose of the E-Z vaccine may have resulted in an immune dysfunction or impairment that left the children vulnerable to other infections. No form of the vaccine has been used in the United States since the Los Angeles trial, but the lower-dose vaccine is still used outside this country.
One death occurred among the Los Angeles children, but it is believed to be unrelated to the vaccine. A 22-month-old boy died of a bacterial infection. He had received the lower dose of E-Z vaccine.
A review by the Office for Protection from Research Risks, part of the Department of Health and Human Services, concluded that the study was scientifically justified but that the CDC and Kaiser had erred in not informing parents that one of the vaccines was experimental.