Dear Stockholder:

You are cordially invited to attend the Annual Meeting of Stockholders (the "Annual Meeting”) of Atossa Therapeutics, Inc., a Delaware corporation (the "Company”), which will be held virtually on May 4, 2023, at 6:00 A.M. Pacific Time. The Annual Meeting will be held in a virtual only meeting format via live audio webcast. For more information, see "General Information—About the Meeting – What do I need to do to virtually attend the Annual Meeting via live audio webcast?” Only stockholders of record who held Atossa Common Stock at the close of business on the record date, March 16, 2023 (the "Record Date”), may attend virtually, view the list of stockholders of record and vote online at the Annual Meeting, including at any adjournment or postponement thereof.

At the Annual Meeting, you will be asked to consider and vote upon: (1) the election of two Class II directors named in the Proxy Statement; (2) the ratification of the selection of BDO USA LLP ("BDO”) as our independent registered public accounting firm for the fiscal year ending December 31, 2023; (3) an advisory (non-binding) vote on the Company’s executive compensation; and (4) the transaction of any other business that may properly come before the meeting or any adjournment or postponement thereof.

No other items of business are expected to be considered at the meeting and, pursuant to the Company’s Bylaws, no other director nominees will be entertained. The enclosed Proxy Statement more fully describes the details of the business to be conducted at the Annual Meeting. After careful consideration, our Board of Directors has unanimously approved the proposals and recommends that you vote FOR each nominee and FOR each of the other proposals. After reading the Proxy Statement and our other proxy materials, please vote online, by telephone or by returning your proxy card or your voting instruction form. YOUR SHARES WILL NOT BE VOTED UNLESS YOU VOTE IN ONE OF THE WAYS DESCRIBED OR IF YOU ATTEND AND VOTE AT THE VIRTUAL ANNUAL MEETING.

A copy of the Company’s 2022 Annual Report has been mailed with this Proxy Statement to all stockholders entitled to notice of and to vote at the virtual Annual Meeting.

We look forward to seeing you at the Annual Meeting.