A fraction of the standard dose of flu vaccine grants people immunity to influenza if injected into the skin rather than into the muscle of the upper arm, the usual target. That's the conclusion of two studies to appear in the Nov. 25 New England Journal of Medicine but released early because of their public health implications.
The technique will not be approved in time to solve this year's vaccine shortage, but it could mitigate future shortages and might also provide a new way to pump up immunity against flu in the elderly.
Injecting vaccines into a thin layer of skin requires more skill than injecting them into relatively thick muscle tissue, which is why muscle injections are standard for most immunizations. But from an immunological point of view, skin is a more attractive target because it brims with immune cells, whereas muscle is almost devoid of them.