Icosavax, Inc. (Nasdaq: ICVX), a biopharmaceutical company leveraging its innovative virus-like particle (VLP) platform technology to develop vaccines against infectious diseases, with an initial focus on life-threatening respiratory diseases, today announced the closing of its initial public offering of 13,953,332 shares of common stock, which includes the exercise in full by the underwriters of their option to purchase 1,819,999 additional shares, at an initial public offering price of $15.00 per share. The aggregate gross proceeds from the offering, before deducting underwriting discounts and commissions and other offering expenses payable by Icosavax, were $209.3 million. Icosavax's common stock is listed on the Nasdaq Global Select Market under the ticker symbol "ICVX."

Jefferies, Cowen, Evercore ISI and William Blair acted as joint book-running managers for the offering.

Registration statements relating to the offering have been filed with the Securities and Exchange Commission and became effective on July 28, 2021. A prospectus relating to and describing the terms of the offering has been filed with the SEC and is available on the SEC's website at www.sec.gov. The offering was made only by means of a prospectus. Copies of the final prospectus may be obtained from Jefferies LLC, Attention: Equity Syndicate Prospectus Department, 520 Madison Avenue, 2nd Floor, New York, NY 10022, or by email at Prospectus_Department@Jefferies.com or by telephone at 877-821-7388; from Cowen and Company, LLC, c/o Broadridge Financial Solutions, Attention: Prospectus Department, 1155 Long Island Avenue, Edgewood, NY 11717, or by email at PostSaleManualRequests@broadridge.com or by telephone at 833-297-2926; from Evercore Group L.L.C., Attention: Equity Capital Markets, 55 East 52nd Street, 35th Floor, New York, New York 10055, or by email at ecm.prospectus@evercore.com or by telephone at 888-474-0200; or from William Blair & Company, L.L.C., Attention: Prospectus Department, 150 North Riverside Plaza, Chicago, IL 60606, or by email at prospectus@williamblair.com or by telephone at 800-621-0687.

This press release shall not constitute an offer to sell or a solicitation of an offer to buy these securities, nor shall there be any offer or sale of these securities in any state or jurisdiction in which such offer, solicitation or sale would be unlawful prior to the registration or qualification under the securities laws of any such state or jurisdiction.

About Icosavax

Icosavax is a biopharmaceutical company leveraging its innovative VLP platform technology to develop vaccines against infectious diseases, with an initial focus on life-threatening respiratory diseases. Icosavax's VLP platform technology is designed to enable multivalent, particle-based display of complex viral antigens, which it believes will induce broad, robust, and durable protection against the specific viruses targeted. Icosavax's pipeline includes vaccine candidates targeting respiratory syncytial virus (RSV), human metapneumovirus (hMPV), and severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Icosavax was formed in 2017 to advance the breakthrough VLP technology from the Institute for Protein Design at the University of Washington with the goal to discover, develop, and commercialize vaccines against infectious diseases. Icosavax exclusively licensed the VLP technology for use in several fields, including RSV and hMPV, from the University of Washington. For SARS-CoV-2, Icosavax has a non-exclusive, worldwide (excluding South Korea) license from the University of Washington that will convert to an exclusive license in North America and Europe in 2025. Icosavax is located in Seattle.