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1.
An exclamation accompanied by an index finger to upper-arm gesture that is quickly self-administered at the first sign of girl or boy "germs". Particularly popular with Australian schoolchildren throughout the 1990s.

Ironically, the injection for life never actually lasted for life, as it was said at every possible opportunity, if not several times a school day.
Jess: Ooh, David just borrowed my eraser and I think I saw him pick his nose earlier!

Stacey, Christine and Sharon: Injection for life!!
by Ginadean February 13, 2009