Background: Acute malaria is a major pediatric problem in developing countries and it is known to be immunosuppressive.
Methods: The serum antibody response to Haemophilus influenzae type b (Hib) conjugate vaccine was investigated in children ages 12 to 30 months with fever associated with malaria, fever associated with other causes or no fever. Groups of 57 children with malaria, 57 children with fever without malaria and 60 healthy children were bled and vaccinated with a single dose of H. influenzae type b capsular polysaccharide-tetanus protein conjugate vaccine. Of these 137 were bled again 1 to 2 months after vaccination.
Results: The median antibody titers at baseline were low and similar in the three groups; 77, 65 and 57% of children in the malaria, febrile and healthy groups, respectively, had prevaccination titers of anti-polyribosylribitol phosphate antibodies below 0.15 microg/ml. The median antibody titers after vaccination were 6.3, 7.5 and 23 microg/ml in the malaria, febrile and healthy groups, respectively (P < 0.001, healthy group vs. the two febrile groups). All the healthy children had protective titers (>0.15 microg/ml) after vaccination, but 11% of the children with malaria and 4% of the other febrile children did not have protective titers.
Conclusions: Anti-polyribosylribitol phosphate titers after Hib vaccination were lower in children with malaria or other febrile illnesses at the time of vaccination than in controls. Fever associated with malaria or other acute illnesses is associated with a diminished response to Hib conjugate vaccine. These findings raise questions about the vaccination of febrile children and indicate the need for further studies in this area.