Abstract
.Equatorial Guinea (EG) has implemented a successful malaria control program on Bioko Island. A highly effective vaccine would be an ideal complement to this effort and could lead to halting transmission and eliminating malaria. Sanaria® PfSPZ Vaccine (Plasmodium falciparum sporozoite Vaccine) is being developed for this purpose. To begin the process of establishing the efficacy of and implementing a PfSPZ Vaccine mass vaccination program in EG, we decided to conduct a series of clinical trials of PfSPZ Vaccine on Bioko Island. Because no clinical trial had ever been conducted in EG, we first successfully established the ethical, regulatory, quality, and clinical foundation for conducting trials. We now report the safety, tolerability, and immunogenicity results of the first clinical trial in the history of the country. Thirty adult males were randomized in the ratio 2:1 to receive three doses of 2.7 × 105 PfSPZ of PfSPZ Vaccine (N = 20) or normal saline placebo (N = 10) by direct venous inoculation at 8-week intervals. The vaccine was safe and well tolerated. Seventy percent, 65%, and 45% of vaccinees developed antibodies to Plasmodium falciparum (Pf) circumsporozoite protein (PfCSP) by enzyme-linked immunosorbent assay, PfSPZ by automated immunofluorescence assay, and PfSPZ by inhibition of sporozoite invasion assay, respectively. Antibody responses were significantly lower than responses in U.S. adults who received the same dosage regimen, but not significantly different than responses in young adult Malians. Based on these results, a clinical trial enrolling 135 subjects aged 6 months to 65 years has been initiated in EG; it includes PfSPZ Vaccine and first assessment in Africa of PfSPZ-CVac. ClinicalTrials.gov identifier: NCT02418962.
Highlights
Malaria has major public health significance in sub-Saharan Africa.[1]
The trial was successful in showing that three doses of 2.7 × 105 PfSPZ of PfSPZ Vaccine were safe, well tolerated, and moderately immunogenic in healthy 18–35-year-old male Equatoguineans living in an area with low malaria exposure
Almost all the vaccinees and controls indicated that there was no pain associated with injection of PfSPZ Vaccine by direct venous inoculation (DVI)
Summary
Malaria has major public health significance in sub-Saharan Africa.[1]. World Health Organization-Global Technical Strategy has set a goal of eliminating malaria from at least 10 malariaendemic countries by the year 2020.2 Development and deployment of new tools such as highly efficacious malaria vaccines that can interrupt malaria transmission will be essential to achieve this goal. The positive control was pooled human sera taken 2 weeks after the last immunization from 12 volunteers immunized four or five times with PfSPZ Vaccine in the VRC 312 clinical trial, who did not develop parasitemia after CHMI.[6] Samples were considered positive if the difference between the post-immunization OD 1.0 and the preimmunization OD 1.0 (net OD 1.0) was 3 50, and the ratio of post-immunization OD 1.0 to pre-immunization OD 1.0 was 3 3.
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