Delivering doses directly to the lungs might give a better immune response than conventional jabs, they say.
There are nearly 180 candidates being explored globally - but none has yet reached the end goal.
About 30 healthy volunteers will be given the vaccines as a mist or aerosol - in the same way asthma drugs are delivered with a nebuliser machine and a mask or mouthpiece.
The seasonal flu jab can also be given as a nasal spray rather than an injection.
Lead researcher Dr Chris Chiu said: "The current pandemic is caused by a respiratory virus which primarily infects people through the cells lining the nose, throat and lungs.
"These surfaces are specialised and produce a different immune response to the rest of the body.
"So it is critical we explore whether targeting the airways directly can provide an effective response compared to a vaccine injected into muscle."
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