Well let’s see….. blow darts are launched through a tube on the mouth with a puff of blown air as a propellant. The darts are usually tipped with poison but perhaps they could put covid vaccine on them instead. Blow darts might be found in jungle settings in Africa which is a little bit racist to suggest using them to administer ia vaccine. Probably they were used in the Amazon jungle and maybe not in African jungles so then it would be less stereotypy due to misconception. However it is clear that the comment was a reference to jungles.
Maybe the nano sprays are already in use