PHASE-I SAFETY AND IMMUNOGENICITY TESTING OF CLINICAL LOTS OF THE SYNTHETIC PLASMODIUM-FALCIPARUM VACCINE SPF66 PRODUCED UNDER GOOD MANUFACTURING PROCEDURE CONDITIONS IN THE UNITED-STATES

Two clinical lots of alum-adsorbed SPf66 vaccine produced in the Unite d States were evaluated in separate, open-label, Phase I clinical tria ls involving 15 healthy, malaria-naive, 18-45-year old men and women. Subjects received 2 mg doses subcutaneously in alternate arms at 0, on e, and six months, Safety was assessed by monitoring local and systemi c reactions and laboratory parameters. The most common side effects we re erythema and local tenderness at the site of injection, which incre ased in frequency with subsequent doses of vaccine. These local reacti ons were considered mild and resolved within 24-48 hr. Eleven of 14 vo lunteers who received all three doses of vaccine seroconverted by enzy me-linked immunosorbent assay. The distribution of high, medium, and l ow nonresponders was comparable with that seen in trials of Colombian- produced vaccine. One high responder developed antibodies reactive wit h asexual stage parasite antigens by immunofluorescence and immunoblot . The results indicated that at full adult doses, SPf66 of U.S. origin is mildly reactogenic and induces immune responses similar to those r eported for SPf66 of Colombian origin.