"Mosquitoes deliver malaria 'vaccine' through bites":

In a daring experiment in Europe, scientists used mosquitoes as flying needles to deliver a "vaccine" of live malaria parasites through their bites.

The results were astounding: Everyone in the vaccine group acquired immunity to malaria; everyone in a non-vaccinated comparison group did not, and developed malaria when exposed to the parasites later.

(Via Howard Roerig.)