144 0001791973 XXXXXXXX LIVE 0001786255 Icosavax, Inc. 001-40655 1930 Boren Avenue Suite 1000 Seattle WA 98101 206-737-0085 Thomas Joseph Russo Officer Common Stock Morgan Stanley Smith Barney LLC

Executive Financial Services 1 New York Plaza, 38th Floor New York NY 10004

10753 166210 50090341 12/20/2023 NASDAQ Common Stock 12/20/2023 Shares acquired upon vesting of restricted stock units Issuer N 29536 12/20/2023 Services Rendered Y Reflects shares to be sold to cover withholding taxes upon vesting of restricted stock unit awards pursuant to a Rule 10b5-1 instruction letter dated December 6, 2021. 12/20/2023 12/06/2021 /s/ Thomas Joseph Russo