X0306 4 2021-08-02 1 0001786255 Icosavax, Inc. ICVX 0001121404 Sanofi 54, RUE LA BOETIE PARIS I0 75008 FRANCE 0 0 1 0 Common Stock (par value, $0.0001) 2021-08-02 4 C 0 3088502 0.00 A 3088502 I Through its wholly-owned subsidiary, Aventis Inc. Common Stock (par value, $0.0001) 2021-08-02 4 P 0 66667 15.00 A 3155169 I Through its wholly-owned subsidiary, Aventis Inc. Series A-1 Preferred Stock (par value, $0.0001) 0.00 2021-08-02 4 C 0 12480498 D Common Stock 3003224 0 I Through its wholly-owned subsidiary, Aventis Inc Series B-1 Preferred Stock (par value, $0.0001) 0.00 2021-08-02 4 C 0 354393 D Common Stock 85278 0 I Through its wholly-owned subsidiary, Aventis Inc 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. Sanofi is the beneficial owner of 3,155,169 Shares of Common Stock of the Issuer through its wholly owned subsidiary, Aventis, Inc. The reporting person acquired additional shares in the Issuer's initial public offering. /s/ Alexander Roger, Head of Securities Law and Capital Markets 2021-08-02