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Safety and reactogenicity of an MSP-1 malaria vaccine candidate: a randomized phase Ib dose-escalation trial in
Mark R Withers1, Denise McKinney, Bernhards R Ogutu
1United States Army Medical Research Unit-Kenya, Nairobi, Kenya. mwithers@us.army.mil
Insights
This study assessed a new malaria vaccine in children, finding it safe and effective. Higher doses of the FMP1/AS02A vaccine showed a superior immune response compared to lower doses.
Area of Science:
- * Clinical vaccinology
- * Infectious disease research
- * Pediatric immunology
Background:
- * Malaria remains a significant global health challenge, particularly in young children.
- * Development of safe and effective malaria vaccines is a priority for disease control.
Purpose of the Study:
- * To evaluate the safety, reactogenicity, and immunogenicity of an investigational malaria vaccine, falciparum malaria protein 1 (FMP1) formulated with AS02A.
- * To determine the optimal dose for eliciting an immune response in children.
Main Methods:
- * Phase Ib, double-blind, randomized, controlled, dose-escalation trial involving 135 children aged 12-47 months in western Kenya.
- * Participants received 10, 25, or 50 microg of FMP1/AS02A or a comparator (rabies vaccine).
- * Safety, reactogenicity, and anti-FMP1 antibody titers were assessed post-vaccination.
Main Results:
- * FMP1/AS02A was safe and well-tolerated, with dose-dependent injection-site reactions but low systemic reactogenicity.
- * Anti-FMP1 antibody titers increased in a dose-dependent manner, with 25 and 50 microg doses eliciting significantly higher and comparable responses.
- * Hemoglobin levels and baseline antibody titers remained stable and similar across all groups.
Conclusions:
- * The FMP1/AS02A malaria vaccine is safe and immunogenic in young children exposed to malaria.
- * Doses of 25 and 50 microg demonstrated a superior immune response compared to the 10 microg dose.
- * Further investigation into this malaria vaccine candidate is warranted.
Objective:
Our aim was to evaluate the safety, reactogenicity, and immunogenicity of an investigational malaria vaccine.
Design:
This was an age-stratified phase Ib, double-blind, randomized, controlled, dose-escalation trial. Children were recruited into one of three cohorts (dosage groups) and randomized in 2:1 fashion to receive either the test product or a comparator.
Setting:
The study was conducted in a rural population in Kombewa Division, western Kenya.
Participants:
Subjects were 135 children, aged 12-47 mo.
Interventions:
Subjects received 10, 25, or 50 microg of falciparum malaria protein 1 (FMP1) formulated in 100, 250, and 500 microL, respectively, of AS02A, or they received a comparator (Imovax (rabies vaccine).
Outcome Measures:
We performed safety and reactogenicity parameters and assessment of adverse events during solicited (7 d) and unsolicited (30 d) periods after each vaccination. Serious adverse events were monitored for 6 mo after the last vaccination.
Results:
Both vaccines were safe and well tolerated. FMP1/AS02A recipients experienced significantly more pain and injection-site swelling with a dose-effect relationship. Systemic reactogenicity was low at all dose levels. Hemoglobin levels remained stable and similar across arms. Baseline geometric mean titers were comparable in all groups. Anti-FMP1 antibody titers increased in a dose-dependent manner in subjects receiving FMP1/AS02A; no increase in anti-FMP1 titers occurred in subjects who received the comparator. By study end, subjects who received either 25 or 50 microg of FMP1 had similar antibody levels, which remained significantly higher than that of those who received the comparator or 10 microg of FMP1. A longitudinal mixed effects model showed a statistically significant effect of dosage level on immune response (F(3,1047) = 10.78, or F(3, 995) = 11.22, p < 0.001); however, the comparison of 25 microg and 50 microg recipients indicated no significant difference (F(1,1047) = 0.05; p = 0.82).
Conclusions:
The FMP1/AS02A vaccine was safe and immunogenic in malaria-exposed 12- to 47-mo-old children and the magnitude of immune response of the 25 and 50 microg doses was superior to that of the 10 microg dose.
