ATOSSA THERAPEUTICS, INC.

Our Annual Report on Form 10-K for the fiscal year ended December 31, 2023, including our audited financial statements, accompanies this Proxy Statement. We will provide a copy of our Annual Report on Form 10-K, free of charge, upon the written or oral request of a stockholder. Please send a written request to our Corporate Secretary at the address set forth below or call the number below. Copies of these materials are also available online through the SEC atwww.sec.gov.

The Company may satisfy SEC rules regarding delivery of proxy statements and annual reports by delivering a single copy of the proxy statement and annual report to an address shared by two or more Company stockholders. This delivery method can result in meaningful cost savings for the Company. In order to take advantage of this opportunity, the Company may deliver only one copy of the proxy statement and annual report to multiple stockholders who share an address, unless contrary instructions are received prior to the mailing date. Similarly, if you share an address with another stockholder and have received multiple copies of our proxy materials, you may write or call us at the address and phone number below to request delivery of a single copy of these materials in the future. We will deliver promptly upon written or oral request, a separate copy of the proxy statement and/or annual report to a stockholder at a shared address to which a single copy of these documents was delivered. If you hold stock as a record stockholder and prefer to receive separate copies of a proxy statement or annual report either now or in the future, please contact the Company’s Corporate Secretary at 107 Spring Street, Seattle, Washington 98104 or by telephone at (866) 893-4927. If your stock is held through a brokerage firm or bank and you prefer to receive separate copies of the proxy statement and/or annual report, or if you received multiple copies of these materials and would prefer to receive a single copy, either now or in the future, please contact your brokerage firm or bank.

Appendix A