The R21/Matrix-M malaria vaccine showed 71%-80% efficacy in preventing cases of malaria in a randomised controlled phase 2 trial published at the end of last year. A phase 3 trial is ongoing.
67 (51%) of 132 children who received R21/Matrix-M with low-dose adjuvant, 54 (39%) of 137 children who received R21/Matrix-M with high-dose adjuvant, and 121 (86%) of 140 children who received the rabies vaccine developed clinical malaria by 12 months
(the rabies vaccine was the control)
The next best thing is the RTS,S/AS01 vaccine, which WHO started rolling out in some pilot programs in 2016 after trials showed its reduced hospital admissions from severe malaria by around 30%, less impressive than R21/Matrix-M.
A few days ago, Ghana's food and drugs administration announced that they've approved the R21/Matrix-M for children aged 5 months to 36 months. It seems like there will be more steps before the vaccines actually start rolling out (they might need to wait for WHO approval and/or the results of the phase 3 trial). In any case, very exciting news.
I found out about this because it is on the In the news section of the front page of Wikipedia.
I agree with this! People get filtered out of the studies for reasons completely beyond their control, even if they really want to join. You just can't help it if your white blood cell count is a tad too low or you have a slight fever the day of study admission.