X0609 4 2026-09-16 0001326190 Altimmune, Inc. ALT 0001595064 Richardson Linda M false 910 CLOPPER ROAD SUITE 201S GAITHERSBURG MD 20878 false true false false Chief Commercial Officer 0 Common Stock, par value $0.0001 2026-09-16 4 M 0 24000 0 A 24000 D Common Stock, par value $0.0001 2026-09-16 4 F 0 6826 3.24 D 17174 D Restricted Stock Units 2026-09-16 4 M 0 24000 0 D Common Stock, par value $0.0001 24000 72000 D Each Restricted Stock Unit ("RSU") represents a contingent right to receive one share of Common Stock, par value $0.0001, when vested. Vesting transaction: Shares surrendered to the Issuer solely to cover taxes associated with vesting of RSUs. The RSUs become vested over four (4) years with 25% of the shares vesting on September 16, 2026, with the remainder vesting in equal annual installments for the following three (3) years, subject to the reporting person's continued service through the applicable vesting date, and have no expiration date. /s/ Gregory Weaver, as Attorney-in-Fact 2026-09-17