One Seattle morning, Carolina Reid sat in a room with nine other volunteers, each waiting to take part in a clinical trial for a new, experimental malaria vaccine.

Reid's turn came. She put her arm over a cardboard box filled with 200 mosquitoes and covered with a mesh that keeps them in but still lets them bite. "Literally a Chinese food takeout container" is how she remembers it. A scientist then covered her arm with a black cloth, because mosquitoes like to bite at night.

Then the feeding frenzy began.

"My whole forearm swelled and blistered," says Reid. "My family was laughing, asking like, 'why are you subjecting yourself to this?'" And she didn't just do it once. She did it five times.

"We use the mosquitoes like they're 1,000 small flying syringes," explains University of Washington, Seattle physician and scientist Dr. Sean Murphy, lead author on a paper in Science Translational Medicine released on August 24 detailing the vaccine trials.

The insects deliver live malaria-causing Plasmodium parasites that have been genetically modified to not get people sick. The body still makes antibodies against the weakened parasite so it's prepared to fight the real thing. //

He and his colleagues went this route because it is costly and time consuming to develop a formulation of a parasite that can be delivered with a needle. The parasites mature inside mosquitoes so at this proof of concept stage – as early stage trials are called — it makes sense to use them for delivery.

"They went old school with this one," says Dr. Kirsten Lyke, a physician and vaccine researcher at the University of Maryland School of Medicine who was not involved in the study. "All things old become new again.