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                              July 15, 2021

       Adam Simpson
       Chief Executive Officer
       Icosavax, Inc.
       1616 East Lake Avenue E., Suite 208
       Seattle, WA 98102

                                                        Re: Icosavax, Inc.
                                                            Registration
Statement on Form S-1
                                                            Filed July 7, 2021
                                                            File No. 333-257733

       Dear Mr. Simpson:

              We have reviewed your registration statement and have the
following comment. In our
       comment, we may ask you to provide us with information so we may better
understand your
       disclosure.

              Please respond to this letter by amending your registration
statement and providing the
       requested information. If you do not believe our comment applies to your
facts and
       circumstances or do not believe an amendment is appropriate, please tell
us why in your
       response.

              After reviewing any amendment to your registration statement and
the information you
       provide in response to this comment, we may have additional comments.

       Correspondence filed July 12, 2021

       Management's Discussion and Analysis of Financial Condition and Results
of Operations
       Critical Accounting Policies
       Common Stock Valuation, page 89

   1.                                                   Please refer to your
response to comment 12 of our letter dated June 14, 2021. When
                                                        available, provide us
with your analysis of the reassessed fair value of common stock
                                                        related to the options
granted in the second quarter of fiscal 2021, as well as the amount of
                                                        compensation expense
you expect to recognize for these grants. Please also explain the
                                                        difference between the
fair value of common stock in the second quarter of fiscal 2021
                                                        and the estimated
offering price.
 Adam Simpson
Icosavax, Inc.
July 15, 2021
Page 2

        We remind you that the company and its management are responsible for
the accuracy
and adequacy of their disclosures, notwithstanding any review, comments, action
or absence of
action by the staff.

       Refer to Rules 460 and 461 regarding requests for acceleration. Please
allow adequate
time for us to review any amendment prior to the requested effective date of
the registration
statement.

       You may contact Julie Sherman at 202-551-3640 or Brian Cascio at
202-551-3676 if you
have questions regarding comments on the financial statements and related
matters. Please
contact Alan Campbell at 202-551-4224 or Suzanne Hayes at 202-551-3675 with any
other
questions.



                                                           Sincerely,
FirstName LastNameAdam Simpson
                                                           Division of
Corporation Finance
Comapany NameIcosavax, Inc.
                                                           Office of Life
Sciences
July 15, 2021 Page 2
cc:       Matthew T. Bush
FirstName LastName