X0306 4 2021-08-02 0 0001786255 Icosavax, Inc. ICVX 0001553470 Gould Terry P C/O ICOSAVAX, INC. 1616 EASTLAKE AVENUE E., SUITE 208 SEATTLE WA 98102 1 0 0 0 Common Stock 2021-08-02 4 C 0 948188 0.00 A 948188 I See footnotes Common Stock 2021-08-02 4 P 0 47981 15.00 A 996169 I See footnotes Common Stock 2021-08-02 4 C 0 916558 0.00 A 916558 I See footnotes Common Stock 2021-08-02 4 P 0 46381 15.00 A 962939 I See footnotes Common Stock 2021-08-02 4 C 0 272131 0.00 A 272131 I See footnotes Common Stock 2021-08-02 4 C 0 352037 0.00 A 352037 I See footnotes Common Stock 2021-08-02 4 C 0 525729 0.00 A 525729 I See footnotes Common Stock 2021-08-02 4 P 0 26604 15.00 A 552333 I See footnotes Common Stock 2021-08-02 4 C 0 244415 0.00 A 244415 I See footnotes Common Stock 2021-08-02 4 P 0 12368 15.00 A 256783 I See footnotes Series A-1 Preferred Stock 0.00 2021-08-02 4 C 0 3631066 D Common Stock 873755 0 I See footnotes Series A-1 Preferred Stock 0.00 2021-08-02 4 C 0 3509939 D Common Stock 844608 0 I See footnotes Series A-1 Preferred Stock 0.00 2021-08-02 4 C 0 1042120 D Common Stock 250768 0 I See footnotes Series A-1 Preferred Stock 0.00 2021-08-02 4 C 0 1348119 D Common Stock 324402 0 I See footnotes Series A-1 Preferred Stock 0.00 2021-08-02 4 C 0 2013269 D Common Stock 484459 0 I See footnotes Series A-1 Preferred Stock 0.00 2021-08-02 4 C 0 935985 D Common Stock 225229 0 I See footnotes Series B-1 Preferred Stock 0.00 2021-08-02 4 C 0 309321 D Common Stock 74432 0 I See footnotes Series B-1 Preferred Stock 0.00 2021-08-02 4 C 0 299003 D Common Stock 71950 0 I See footnotes Series B-1 Preferred Stock 0.00 2021-08-02 4 C 0 88775 D Common Stock 21362 0 I See footnotes Series B-1 Preferred Stock 0.00 2021-08-02 4 C 0 114843 D Common Stock 27635 0 I See footnotes Series B-1 Preferred Stock 0.00 2021-08-02 4 C 0 171505 D Common Stock 41269 0 I See footnotes Series B-1 Preferred Stock 0.00 2021-08-02 4 C 0 79734 D Common Stock 19186 0 I See footnotes On August 2, 2021, the shares of Series A-1 Preferred Stock and Series B-1 Preferred Stock converted into shares of the Issuer's common stock at a ratio of 4.1557-for-1 automatically upon the closing of the Issuer's initial public offering without payment or further consideration. The shares have no expiration date. As a result of the Issuer's initial public offering, the reporting person is no longer a 10% owner of the Issuer and is therefore no longer subject to Section 16 in connection with its transactions in the equity securities of the Issuer. The shares are held directly by Adams Street Venture/Growth Fund VI LP ("ASVG VI"). The shares are held directly by Adams Street Growth Equity Fund VII LP ("AS GE VII"). The shares are held directly by Adams Street 2016 Direct Venture/Growth Fund LP ("AS 2016"). The shares are held directly by Adams Street 2017 Direct Venture/Growth Fund LP ("AS 2017"). The shares are held directly by Adams Street 2018 Direct Venture/Growth Fund LP ("AS 2018"). The shares are held directly by Adams Street 2019 Direct Growth Equity Fund LP ("AS 2019"). Adams Street Partners, LLC as the managing member of the general partner of the general partner of ASVG VI, AS GE VII, AS 2016, AS 2017, AS 2018 and AS 2019 (collectively the "Funds"), may be deemed to beneficially own the shares held by the Funds. Thomas S. Bremner, Jeffrey T. Diehl, Elisha P. Gould III, Robin P. Murray and Fred Wang, each of whom is a partner of Adams Street Partners, LLC (or a subsidiary thereof), may be deemed to have shared voting and investment power over the shares held by the Funds. Adams Street Partners, LLC and Thomas S. Bremner, Jeffrey T. Diehl, Elisha P. Gould, Robin Murray and Fred Wang disclaim beneficial ownership of the shares held by the Funds except to the extent of their pecuniary interest therein. Includes additional shares of Common Stock as a result of the conversion of Preferred Stock calculated on an aggregate basis of all shares of Preferred Stock held by the holder. ASVG VI acquired additional shares in the Issuer's initial public offering. AS GE VII acquired additional shares in the Issuer's initial public offering. AS 2018 acquired additional shares in the Issuer's initial public offering. AS 2019 acquired additional shares in the Issuer's initial public offering. /s/ Thomas Russo, Attorney-in-Fact 2021-08-03