By injecting viruses and bacteria. Takes very little of that to multiply and kill you.
If they're trying to vaccinate us it would take a lot more than a skeeter could deliver.
Actually, it takes very little. Mosquitoes are Carriers. They carry death all over the globe. An elementary Microbiology Course would make that evident.
If it’s okay with you, I’ll continue to distrust the commies, and continue to presume that everything they do is in furtherance of their war against humans.