I used to give sub-q vaccines to my kitties, as well as feline rescues and fosters. The information on over vaccination, vaccination reactions requiring epinephrine, as well as vaccination sight melanomas, gave me the desire to look for options. Not only is the Ultranasal FVRCP safer in that respect, but it also INSTANTANEOUS! Because it is directly applied to the membranes, the effectiveness starts immediately! And, I have had no problems with reactions or cancers! I'm SOLD! Thank you, Revival, for offering a wide range of products for everyone's needs!