As a malaria researcher (NOT in vaccines, but I try to keep up with this stuff as best I can), I just want to highlight a few issues with the RTS,S vaccine.

First, in the major clinical trials published in 2015, the vaccine was found to prevent 1 case (confidence interval of -2 to 4) of fatal malaria. So it's not apparently effective at preventing death.

It was 36.3% (CI 31.8 to 40.5) effective in reducing clinical malaria burden, which is essentially fever and 32.2% (CI 13.7 to 46.9) in preventing more adverse clinical outcomes dubbed "severe malaria".

It's hard to know whether this vaccine prevents people from getting infected, or prevents the infection from gathering enough steam to cause a clinical effect. This is important because in the former case, it would help reduce transmission. This would be great, but as far as I know, hasn't been studied.

There are also issues of genotype and adaptability of the parasite. since RTS,S targets a surface antigen (as many/most vaccines do), there will be significant selection pressure on the parasite, and the effectiveness of the vaccine may be reduced over time. Parasites are more hardy than viruses, and this adaptation can be a big issue. In this vein, the vaccine is more effective in some locations compared to others (I presume based on the dominant RTS,S phenotype in the area).

It's also worth noting that GlaxoSmithKline, the Gates Foundation, and others have a very vested interest in this vaccine succeeding, and are throwing buckets of money at it.

I am optimistic and everybody would love to see malaria burden reduced, but there are (as always) reasons to be cautious.