According to Chen, these findings confirm the results of previous studies and suggest that the AAP recommendations regarding vaccination with DPT are still valid. These recommendations are that infants with a history of convulsions not receive DPT until their neurologic conditions are clearly determined. Once determined, they should then receive diphtheria and tetanus toxoids (DT) unless the seizure disorder is controlled, in which case they should receive DPT. ACIP has concluded that a family history of febrile convulsions should not deter infants from receiving DPT (CDC, 1993). More rigorous controlled studies need to be conducted, however, to assess firmly the risk of convulsions following vaccination with DPT in infants with a personal or family history of febrile or afebrile convulsions.
CDC is conducting a large controlled study of the risk of convulsions following vaccination with DPT in infants who are neurologically impaired or considered at risk of being neurologically impaired because of a number of factors, including being born prematurely, deprived of oxygen during birth, or developmentally delayed. This study will use data in the Large Linked Database (LLDB), a CDC-coordinated linkage of four large health maintenance organizations' databases. Comprised of automated data for nearly 500,000 children in Oregon, Washington, and California, the LLDB includes information on hospital, outpatient and emergency department utilization. Using these files, researchers can identify children who are neurologically impaired or at risk of such impairments, and assess their response following vaccination with DPT in comparison with children not recently vaccinated. According to Davis, the number of children in the study is large enough to determine with relatively high statistical confidence whether children with neurologic impairments or at risk for neurologic impairment are at increased risk for experiencing convulsions following vaccination with DPT.
In most developing countries, infants receive the measles vaccine at 9 months of age. Because there is a high rate of transmission of measles in infants younger than this among certain populations in developing countries, the World Health Organization (WHO) recommended in 1989 that infants in these populations receive a high-titer, live attenuated measles vaccine at 6 months of age. To prompt a protective immune response in younger infants, the high-titer measles vaccine has more measles antigen than the standard measles vaccine.