Document And Entity Information - shares	3 Months Ended
	Mar. 31, 2021	May 05, 2021
Document Information [Line Items]
Entity Central Index Key	0000072444
Entity Registrant Name	Vaxart, Inc.
Amendment Flag	false
Current Fiscal Year End Date	--12-31
Document Fiscal Period Focus	Q1
Document Fiscal Year Focus	2021
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Mar. 31, 2021
Document Transition Report	false
Entity File Number	001-35285
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	59-1212264
Entity Address, Address Line One	170 Harbor Way, Suite 300
Entity Address, City or Town	South San Francisco
Entity Address, State or Province	CA
Entity Address, Postal Zip Code	94080
City Area Code	650
Local Phone Number	550-3500
Title of 12(b) Security	Common stock, $0.0001 par value
Trading Symbol	VXRT
Security Exchange Name	NASDAQ
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Common Stock, Shares Outstanding		122,268,453