| Document And Entity Information | Sep. 13, 2021 |
| Document Information [Line Items] | |
| Entity, Registrant Name | Vaxart, Inc. |
| Document, Type | 8-K/A |
| Document, Period End Date | Sep. 13, 2021 |
| Entity, Incorporation, State or Country Code | DE |
| Entity, File Number | 001-35285 |
| Entity, Tax Identification Number | 59-1212264 |
| Entity, Address, Address Line One | 170 Harbor Way |
| Entity, Address, Address Line Two | 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 |
| Written Communications | false |
| Soliciting Material | false |
| Pre-commencement Tender Offer | false |
| Pre-commencement Issuer Tender Offer | false |
| Title of 12(b) Security | Common stock |
| Trading Symbol | VXRT |
| Security Exchange Name | NASDAQ |
| Entity, Emerging Growth Company | false |
| Amendment Description | Form 8-K/A date of report 09-13-21 |
| Amendment Flag | true |
| Entity, Central Index Key | 0000072444 |
