Check out this article from popsci.com. They have successfully released genetically modified mosquitoes onto an island. The mosquitoes they released have lowered the populations by as much as 80%. They say it's safe, since the mosquitoes they release are sterile and can't reproduce.
"An Oxford-based research firm has announced the results of a release of genetically modified male mosquitoes in the Cayman Islands, the first experiment with GM mosquitoes to take place in the wild.
From May to October of this year, Oxitec released male mosquitoes three times a week in a 40-acre area. The mosquitoes had been genetically modified to be sterile, so that when they mated with the indigenous female mosquitoes there would be no offspring, and the population would shrink.
Mosquito numbers in the region had dropped 80 percent by August, which the researchers expect would result in fewer dengue cases."
Check out the original article on popsci.com