Fig. 4

Functional transmission-reducing activity in SMFA. A SMFA with participants’ sera collected two weeks after the third and fourth immunisation. Each data point represents the transmission-reducing activity of participants’ sera compared to their pre-immunisation sera. B SMFA with purified and concentrated anti-R0.6C IgGs from sera of a selection of six participants collected at 2 weeks after the fourth immunisation. Two sera from the 30 µg R0.6C/AlOH + Matrix M, 100 µg R0.6C/AlOH and 100 µg R0.6C/AlOH + Matrix M arms were selected based on anti-6C antibody concentrations (ranging 7.2–20.3 µg/mL). C Correlation between anti-6C IgG serum concentrations and transmission-reducing activity of the concentrated IgGs purified therefrom (Spearman’s ρ = 1.00, p = 0.0028). Dashed lines at 80% indicate the predefined efficacy threshold of interest [4, 26]. Asterisks indicate TRA is statistically significantly higher than the threshold of 80%