So this is using mosquitos to deliver an attenuated malaria sporozoite, as a malaria vaccine, which is very clever, since the mosquitos are the normal vector for malaria, which causes vast mortality and morbidity, and huge economic damage across the world. Only recently have useful-looking vaccines been clinically demonstrated, and these are not yet available. One problem is that the disease is endemic in many parts of the world where vaccination programmes are difficult, so use of mosquitos is interesting and pragmatic.
There are obvious ethical problems: individual consent is impossible. Also, environmental impact assessments will set a very high bar against unintended consequences.