The briefest possible act of
sexual intercourse. There is no "pumping" involved - just insertion,
ejaculation, and withdrawal.
Although very similar physically to a "one-pump wonder," but a flu shot is different because it is a deliberate act meant to save time. A flu shot requires training to
accomplish correctly. A flu shot is a valuable scheduling tool.
Men generally enjoy giving flu shots more than women enjoy receiving them, but with discipline women should be able to train their bodies to orgasm from a single flu shot.