Schedule 13G Name of issuer: Icosavax, Inc. Title of class of securities: Common Stock Cusip: 45114M109 Date of event which requires filing: 12/31/2022 Rule 13d-1(b) 1. Platinum Investment Management Limited 2. (b) 3. 4. Sydney Australia 5. Platinum Investment Management Limited 2,095,181 (5.25%) Note:Combined total of underlying managed funds 6. N/A 7. Platinum Investment Management Limited 2,249,711 (5.64%) Note:Combined total of underlying managed funds 8. N/A 9. 2,249,711 10. No 11. 5.64% 12. IA Item 1. (a) Icosavax, Inc. (b) 1930 BOREN AVE. SUITE 1000 SEATTLE, WA 98101 USA Item 2. (a) Platinum Investment Management Limited (b) Level 8, 7 Macquarie Place Sydney NSW 2000 Australia (c) Australia (d) Common Stock (e) 45114M109 Item 3. (e) An IA in accordance with Section 240.13d-1(b)(1)(ii)(e) Item 4. (a) 2,249,711 (b) 5.64% (c) (i) 2,095,181 (ii) 0 (iii) 2,249,711 (iv) 0 Item 5 No Item 6 The clients of Platinum Investment Management Ltd including pooled investment vehicles and other managed accounts have the right to receive or power to direct the receipt of dividends from, and the proceeds from the sale of, Icosavax, Inc. Item 7 N/A Item 8 N/A Item 9 N/A Item 10 (a) By signing below, I certify that to the best of my knowledge and belief, the securities referred to above were acquired and are held in the ordinary course of business and were not acquired and are not held for the purpose of or with the effect of changing or influencing the control of the issuer of the securities and were not acquired and are not held in connection with or as a participant in any transaction having that purpose or effect. (b) N/A After reasonable inquiry and to the best of my knowledge and belief, I certify that the information set forth in this statement is true, complete and correct.