Note 6 - Liabilities Related to Sale of Future Royalties (Details Textual) - HCRP [Member] $ in Millions	1 Months Ended
Apr. 30, 2016 USD ($)
Proceeds from Sale of Future Royalties, Net	$ 20
Royalty Interest Due Each Year	$ 3
Royalty Interest, Percentage of Additional Royalties Due Each Year	15.00%
Royalty Interest, Additional Royalties Due Each Year	$ 1

Amount of royalty interest due each year as per the terms of the Royalty Interest Acquisition Agreement.

No definition available.

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Namespace Prefix:	vxrt_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant