Note 11 - Segment Reporting - Schedule of Segment Reporting Information, by Segment (Details) - USD ($) $ in Thousands		3 Months Ended		9 Months Ended
		Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2025	Sep. 30, 2024
Revenues		$ 72,413	$ 4,933	$ 133,019	$ 13,515
Research and Development Expense		75,947	15,066	156,426	51,559
General and administrative		4,277	4,342	13,942	16,757
Interest income		(302)	(1,022)	(1,049)	(1,941)
Non-cash interest expense related to sale of future royalties		608	631	2,277	2,045
Income Tax Expense (Benefit)		17	18	132	84
Net loss		(8,141)	(14,080)	(38,718)	(54,963)
Adjustments and reconciling items		(8,141)	(14,080)	(38,718)	(54,963)
Operating Segments [Member]
Revenues		72,413	4,933	133,019	13,515
General and administrative		4,277	4,342	13,942	16,757
Interest income		(302)	(1,022)	(1,049)	(1,941)
Non-cash interest expense related to sale of future royalties		608	631	2,277	2,045
Other segment items(A)	[1]	7	(22)	9	(26)
Income Tax Expense (Benefit)		17	18	132	84
Net loss		(8,141)	(14,080)	(38,718)	(54,963)
Adjustments and reconciling items		(8,141)	(14,080)	(38,718)	(54,963)
Operating Segments [Member] | Norovirus Program [Member]
Research and Development Expense		519	821	3,227	2,560
Operating Segments [Member] | Covid-19 Program [Member]
Research and Development Expense		66,220	1,513	118,413	7,849
Operating Segments [Member] | Other Programs [Member]
Research and Development Expense		0	2	346	16
Operating Segments [Member] | Preclinical Research [Member]
Research and Development Expense		98	216	722	1,596
Operating Segments [Member] | Process Development Program [Member]
Research and Development Expense		0	106	46	189
Operating Segments [Member] | Internal Research and Development Costs [Member]
Research and Development Expense		9,110	12,408	33,672	39,349
Segment Reporting, Reconciling Item, Excluding Corporate Nonsegment [Member]
Net loss		0	0	0	0
Adjustments and reconciling items		$ 0	$ 0	$ 0	$ 0

[1] Other segment items included in other income (expense), net.