BACKGROUND:

For over 20 years children with sickle cell anemia have been known to have an increased susceptibility to severe bacterial infection, particularly due to Streptococcus pneumoniae. Meningitis, pneumonia and septicemia due to this organism have been recognized as the major causes of death for these children, with children under three years of age being at highest risk. The annual incidence of pneumococcal septicemia among young children with sickle cell anemia appears to have remained remarkably constant over the last two decades at approximately 10 percent. This illness can often be fulminant, progressing from the onset of fever to death in less than 12 hours, with a case fatality rate ranging as high as 35 percent.

Penicillin prophylaxis has been advocated as a preventive measure against severe pneumococcal infections in children with sickle cell anemia. One study had shown that the risk of pneumococcal infection in these children could be reduced by the use of parenteral penicillin.

DESIGN NARRATIVE:

Phase I was a multi-center, randomized, double-blind, placebo-controlled trial. One hundred and five patients were assigned to the penicillin group and 110 to placebo. The primary endpoint was a documented severe infection due to S. pneumoniae. The secondary endpoint was a severe infection due to an organism other than S. pneumoniae.

Because data were not available to define the age at which prophylactic penicillin could be safely discontinued, the NHLBI launched Phase II of the Prophylactic Penicillin Study beginning in 1987. Recruitment ended in August, 1993. The clinical phase of Phase II ended in August, 1994.

Phase II was a multi-center randomized trial to evaluate the hazards of discontinuing daily oral penicillin at the age of five years. Within three months of their fifth birthdays, all children were randomized to continue oral penicillin prophylaxis or to stop prophylaxis. Each child was followed for a minimum of two years. The primary endpoint was a comparison of documented pneumococcal infection in children continuing penicillin after five years of age versus children whose prophylaxis was stopped at five years of age. Ancillary studies conducted in subsets of patients included: the prevalence of colonization of the nasopharynx with antibiotic resistant microorangisms; and the relationship of antibody response to pneumococcal vaccination to the incidence of pneumococcal sepsis in this patient population.