Natural immunity to malaria is often limited to the local variant -- go a couple hundred miles, and you have no resistance at all. Vaccines rely on the body's natural immune system, so it is nearly impossible to create a single vaccine that is effective across the world.
For this reason, I'm highly skeptical that this initial test result will hold up with broader trials. BTW my spouse is a malariologist, formerly at WHO, and I've been a witness to much of the fight against malaria over the years.