No crashingly obvious turned-the-litmus-paper-pink “hey, it works!” test results, but it kinda-sorta suggests that it might possibly work. Or at least help a little bit.
When I was a kid, my Mom used to use either Vicks or Musterole on my chest with a piece of wool flannel covering it to keep my chest warm. It really worked for me.
I was always under the impression that the deceptive “cool” sensation from the mint derivative in it would fool the patient into thinking that air was starting to pass through clogged sinuses and lungs. In any event, Vaporub never did me any good. The only thing that ever unclogs my chest is lots of steam from a piping hot shower.