ALT

SEC source: 0001705905-26-000004 · form4-01292026_040101.xml · nonDerivative · entry 2

Roberts M Scot · CIK 0001705905 · Chief Scientific Officer

10b5-1 filing: No plan indicated

Ownership: Direct

Disclosed balance after: 95,395

F2 · kind: Vesting transaction: Shares surrendered to the Issuer solely to cover taxes associated with vesting of RSUs.

SEC source: 0001705905-26-000004 · form4-01292026_040101.xml · nonDerivative · entry 1

Roberts M Scot · CIK 0001705905 · Chief Scientific Officer

10b5-1 filing: No plan indicated

Ownership: Direct

Disclosed balance after: 100,143

Exercise/conversion can include RSU settlement. Transaction price and option strike are different fields; a missing price is not zero. Derivative and underlying rows can describe the same event.

F1 · price: Each Restricted Stock Unit ("RSU") represents a contingent right to receive one share of Common Stock, par value $0.0001, when vested.

SEC source: 0001960780-26-000004 · form4-01272026_070101.xml · derivative · entry 3

Jordt Raymond M · CIK 0001960780 · Chief Business Officer

10b5-1 filing: No plan indicated

Ownership: Direct

Disclosed balance after: 29,200

Underlying: Common Stock, par value $0.0001 · 14,600 shares

Expires not disclosed

Exercise/conversion can include RSU settlement. Transaction price and option strike are different fields; a missing price is not zero. Derivative and underlying rows can describe the same event.

F1 · derivative.exercise_price: Each Restricted Stock Unit ("RSU") represents a contingent right to receive one share of Common Stock, par value $0.0001, when vested.

F3 · derivative.exercise_date: The RSUs vest in substantially equal annual installments over the 4 years following January 25, 2024, subject to the reporting person's continued service through the applicable vesting date, and have no expiration date.

F3 · derivative.expiration_date: The RSUs vest in substantially equal annual installments over the 4 years following January 25, 2024, subject to the reporting person's continued service through the applicable vesting date, and have no expiration date.

SEC source: 0001960780-26-000004 · form4-01272026_070101.xml · nonDerivative · entry 2

Jordt Raymond M · CIK 0001960780 · Chief Business Officer

10b5-1 filing: No plan indicated

Ownership: Direct

Disclosed balance after: 53,915

F2 · kind: Vesting transaction: Shares surrendered to the Issuer solely to cover taxes associated with vesting of RSUs.

SEC source: 0001960780-26-000004 · form4-01272026_070101.xml · nonDerivative · entry 1

Jordt Raymond M · CIK 0001960780 · Chief Business Officer

10b5-1 filing: No plan indicated

Ownership: Direct

Disclosed balance after: 57,770

Exercise/conversion can include RSU settlement. Transaction price and option strike are different fields; a missing price is not zero. Derivative and underlying rows can describe the same event.

F1 · price: Each Restricted Stock Unit ("RSU") represents a contingent right to receive one share of Common Stock, par value $0.0001, when vested.

SEC source: 0001705905-26-000002 · form4-01272026_070101.xml · derivative · entry 3

Roberts M Scot · CIK 0001705905 · Chief Scientific Officer

10b5-1 filing: No plan indicated

Ownership: Direct

Disclosed balance after: 29,200

Underlying: Common Stock, par value $0.0001 · 14,600 shares

Expires not disclosed

Exercise/conversion can include RSU settlement. Transaction price and option strike are different fields; a missing price is not zero. Derivative and underlying rows can describe the same event.

F1 · derivative.exercise_price: Each Restricted Stock Unit ("RSU") represents a contingent right to receive one share of Common Stock, par value $0.0001, when vested.

F3 · derivative.exercise_date: The RSUs vest in substantially equal annual installments over the 4 years following January 25, 2024, subject to the reporting person's continued service through the applicable vesting date, and have no expiration date.

F3 · derivative.expiration_date: The RSUs vest in substantially equal annual installments over the 4 years following January 25, 2024, subject to the reporting person's continued service through the applicable vesting date, and have no expiration date.

SEC source: 0001705905-26-000002 · form4-01272026_070101.xml · nonDerivative · entry 2

Roberts M Scot · CIK 0001705905 · Chief Scientific Officer

10b5-1 filing: No plan indicated

Ownership: Direct

Disclosed balance after: 84,293

F2 · kind: Vesting transaction: Shares surrendered to the Issuer solely to cover taxes associated with vesting of RSUs.

SEC source: 0001705905-26-000002 · form4-01272026_070101.xml · nonDerivative · entry 1

Roberts M Scot · CIK 0001705905 · Chief Scientific Officer

10b5-1 filing: No plan indicated

Ownership: Direct

Disclosed balance after: 88,666

Exercise/conversion can include RSU settlement. Transaction price and option strike are different fields; a missing price is not zero. Derivative and underlying rows can describe the same event.

F1 · price: Each Restricted Stock Unit ("RSU") represents a contingent right to receive one share of Common Stock, par value $0.0001, when vested.

SEC source: 0001515813-26-000002 · form4-01272026_070101.xml · derivative · entry 3

Garg Vipin K · CIK 0001515813 · Director

10b5-1 filing: No plan indicated

Ownership: Direct

Disclosed balance after: 84,100

Underlying: Common Stock, par value $0.0001 · 42,050 shares

Expires not disclosed

Exercise/conversion can include RSU settlement. Transaction price and option strike are different fields; a missing price is not zero. Derivative and underlying rows can describe the same event.

F1 · derivative.exercise_price: Each Restricted Stock Unit ("RSU") represents a contingent right to receive one share of Common Stock, par value $0.0001, when vested.

F3 · derivative.exercise_date: The RSUs vest in substantially equal annual installments over the 4 years following January 25, 2024, subject to the reporting person's continued service through the applicable vesting date, and have no expiration date.

F3 · derivative.expiration_date: The RSUs vest in substantially equal annual installments over the 4 years following January 25, 2024, subject to the reporting person's continued service through the applicable vesting date, and have no expiration date.

SEC source: 0001515813-26-000002 · form4-01272026_070101.xml · nonDerivative · entry 2

Garg Vipin K · CIK 0001515813 · Director

10b5-1 filing: No plan indicated

Ownership: Direct

Disclosed balance after: 379,148

F2 · kind: Vesting transaction: Shares surrendered to the Issuer solely to cover taxes associated with vesting of RSUs.

SEC source: 0001515813-26-000002 · form4-01272026_070101.xml · nonDerivative · entry 1

Garg Vipin K · CIK 0001515813 · Director

10b5-1 filing: No plan indicated

Ownership: Direct

Disclosed balance after: 397,132

Exercise/conversion can include RSU settlement. Transaction price and option strike are different fields; a missing price is not zero. Derivative and underlying rows can describe the same event.

F1 · price: Each Restricted Stock Unit ("RSU") represents a contingent right to receive one share of Common Stock, par value $0.0001, when vested.

SEC source: 0001743611-26-000002 · form4-01092026_040101.xml · nonDerivative · entry 1

Pisano Wayne · CIK 0001743611 · Director

10b5-1 filing: No plan indicated

Ownership: Direct

Disclosed balance after: 13,498

SEC source: 0001555132-26-000002 · form4-01052026_040104.xml · nonDerivative · entry 1

Sohn Catherine A. · CIK 0001555132 · Director

10b5-1 filing: No plan indicated

Ownership: Direct

Disclosed balance after: 1,500

SEC source: 0001960780-26-000002 · form4-01052026_040114.xml · derivative · entry 3

Jordt Raymond M · CIK 0001960780 · Chief Business Officer

10b5-1 filing: No plan indicated

Ownership: Direct

Disclosed balance after: 9,375

Underlying: Common Stock, par value $0.0001 · 9,375 shares

Expires not disclosed

Exercise/conversion can include RSU settlement. Transaction price and option strike are different fields; a missing price is not zero. Derivative and underlying rows can describe the same event.

F1 · derivative.exercise_price: Each Restricted Stock Unit ("RSU") represents a contingent right to receive one share of Common Stock, par value $0.0001, when vested.

F3 · derivative.exercise_date: RSUs become vested and released over four (4) years with 25% of the shares vesting on January 1, 2024, 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.

F3 · derivative.expiration_date: RSUs become vested and released over four (4) years with 25% of the shares vesting on January 1, 2024, 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.

SEC source: 0001960780-26-000002 · form4-01052026_040114.xml · nonDerivative · entry 2

Jordt Raymond M · CIK 0001960780 · Chief Business Officer

10b5-1 filing: No plan indicated

Ownership: Direct

Disclosed balance after: 43,170

F2 · kind: Vesting transaction: Shares surrendered to the Issuer solely to cover taxes associated with vesting of RSUs.

SEC source: 0001960780-26-000002 · form4-01052026_040114.xml · nonDerivative · entry 1

Jordt Raymond M · CIK 0001960780 · Chief Business Officer

10b5-1 filing: No plan indicated

Ownership: Direct

Disclosed balance after: 45,645

Exercise/conversion can include RSU settlement. Transaction price and option strike are different fields; a missing price is not zero. Derivative and underlying rows can describe the same event.

F1 · price: Each Restricted Stock Unit ("RSU") represents a contingent right to receive one share of Common Stock, par value $0.0001, when vested.

SEC source: 0001527204-25-000005 · form4-12292025_041201.xml · nonDerivative · entry 1

Jorkasky Diane · CIK 0001527204 · Director

10b5-1 filing: No plan indicated

Ownership: Direct

Disclosed balance after: 527

SEC source: 0001409939-25-000005 · form4-12232025_041201.xml · nonDerivative · entry 1

GILL JOHN · CIK 0001409939 · Director

10b5-1 filing: No plan indicated

Ownership: Direct

Disclosed balance after: 12,500

SEC source: 0001698665-25-000005 · form4-12222025_091234.xml · nonDerivative · entry 1

Durso Jerome Benedict · CIK 0001698665 · Director

10b5-1 filing: No plan indicated

Ownership: Direct

Disclosed balance after: 12,500

F1 · price: The price reported in Column 4 is a weighted average price. These shares were purchased in multiple transactions at prices ranging from $4.1200 to $4.1300, inclusive. The reporting person undertakes to provide to Altimmune, Inc., any security holder of Altimmune, Inc., or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares purchased at each separate price within the ranges set forth in this footnote

SEC source: 0001104659-25-117451 · tm2532516-1_4seq1.xml · derivative · entry 2

Durso Jerome Benedict · CIK 0001698665 · Director · CEO-elect

10b5-1 filing: No plan indicated

Ownership: Direct

Disclosed balance after: 633,700

Underlying: Common Stock, par value $0.0001 · 633,700 shares

Expires not disclosed

F2 · derivative.exercise_price: Each Restricted Stock Unit ("RSU") represents a contingent right to receive one share of Common Stock, par value $0.0001, when vested.

F3 · derivative.exercise_date: The RSUs become vested over four (4) years with 25% of the shares vesting December 1, 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.

F3 · derivative.expiration_date: The RSUs become vested over four (4) years with 25% of the shares vesting December 1, 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.

SEC source: 0001104659-25-117451 · tm2532516-1_4seq1.xml · derivative · entry 1

Durso Jerome Benedict · CIK 0001698665 · Director · CEO-elect

10b5-1 filing: No plan indicated

Ownership: Direct

Disclosed balance after: 1,824,400

Underlying: Common Stock, par value $0.0001 · 1,824,400 shares

Expires 2035-12-01

F1 · derivative.exercise_date: The shares underlying the option become vested and exercisable over four (4) years with 25% of the shares vesting on December 1, 2026, with the remainder vesting in equal monthly installments for the following thirty-six (36) months, subject to the reporting person's continued service on each applicable vesting date.

SEC source: 0001251779-25-000006 · form4-11122025_091117.xml · derivative · entry 3

WEAVER GREGORY L · CIK 0001251779 · Chief Financial Officer

10b5-1 filing: No plan indicated

Ownership: Direct

Disclosed balance after: 56,250

Underlying: Common Stock, par value $0.0001 · 18,750 shares

Expires not disclosed

Exercise/conversion can include RSU settlement. Transaction price and option strike are different fields; a missing price is not zero. Derivative and underlying rows can describe the same event.

F1 · derivative.exercise_price: Each Restricted Stock Unit ("RSU") represents a contingent right to receive one share of Common Stock, par value $0.0001, when vested.

F3 · derivative.exercise_date: The RSUs become vested over four (4) years with 25% of the shares vesting on November 11, 2025, 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.

F3 · derivative.expiration_date: The RSUs become vested over four (4) years with 25% of the shares vesting on November 11, 2025, 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.

SEC source: 0001251779-25-000006 · form4-11122025_091117.xml · nonDerivative · entry 2

WEAVER GREGORY L · CIK 0001251779 · Chief Financial Officer

10b5-1 filing: No plan indicated

Ownership: Direct

Disclosed balance after: 23,078

F2 · kind: Vesting transaction: Shares surrendered to the Issuer solely to cover taxes associated with vesting of RSUs.

SEC source: 0001251779-25-000006 · form4-11122025_091117.xml · nonDerivative · entry 1

WEAVER GREGORY L · CIK 0001251779 · Chief Financial Officer

10b5-1 filing: No plan indicated

Ownership: Direct

Disclosed balance after: 28,750

Exercise/conversion can include RSU settlement. Transaction price and option strike are different fields; a missing price is not zero. Derivative and underlying rows can describe the same event.

F1 · price: Each Restricted Stock Unit ("RSU") represents a contingent right to receive one share of Common Stock, par value $0.0001, when vested.

SEC source: 0001104659-25-096679 · tm2527887-3_4seq1.xml · derivative · entry 2

WEAVER GREGORY L · CIK 0001251779 · Chief Financial Officer

10b5-1 filing: No plan indicated

Ownership: Direct

Disclosed balance after: 57,900

Underlying: Common Stock, par value $0.0001 · 57,900 shares

Expires not disclosed

F2 · derivative.exercise_price: Each Restricted Stock Unit ("RSU") represents a contingent right to receive one share of Common Stock, par value $0.0001, when vested

F3 · derivative.exercise_date: The RSUs become vested over four (4) years with 25% of the shares vesting October 1, 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.

F3 · derivative.expiration_date: The RSUs become vested over four (4) years with 25% of the shares vesting October 1, 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.

SEC source: 0001104659-25-096679 · tm2527887-3_4seq1.xml · derivative · entry 1

WEAVER GREGORY L · CIK 0001251779 · Chief Financial Officer

10b5-1 filing: No plan indicated

Ownership: Direct

Disclosed balance after: 166,800

Underlying: Common Stock, par value $0.0001 · 166,800 shares

Expires 2035-10-01

F1 · derivative.exercise_date: The shares underlying the option become vested and exercisable over four (4) years with 25% of the shares vesting on October 1, 2026, with the remainder vesting in equal monthly installments for the following thirty-six (36) months, subject to the reporting person's continued service on each applicable vesting date.

SEC source: 0001104659-25-096678 · tm2527887-2_4seq1.xml · derivative · entry 2

Arbet-Engels Christophe · CIK 0001802615 · Chief Medical Officer

10b5-1 filing: No plan indicated

Ownership: Direct

Disclosed balance after: 150,000

Underlying: Common Stock, par value $0.0001 · 150,000 shares

Expires not disclosed

F2 · derivative.exercise_price: Each Restricted Stock Unit ("RSU") represents a contingent right to receive one share of Common Stock, par value $0.0001, when vested

F3 · derivative.exercise_date: The RSUs become vested over four (4) years with 25% of the shares vesting October 1, 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.

F3 · derivative.expiration_date: The RSUs become vested over four (4) years with 25% of the shares vesting October 1, 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.

SEC source: 0001104659-25-096678 · tm2527887-2_4seq1.xml · derivative · entry 1

Arbet-Engels Christophe · CIK 0001802615 · Chief Medical Officer

10b5-1 filing: No plan indicated

Ownership: Direct

Disclosed balance after: 450,000

Underlying: Common Stock, par value $0.0001 · 450,000 shares

Expires 2035-10-01

F1 · derivative.exercise_date: The shares underlying the option become vested and exercisable over four (4) years with 25% of the shares vesting on October 1, 2026, with the remainder vesting in equal monthly installments for the following thirty-six (36) months, subject to the reporting person's continued service on each applicable vesting date.

SEC source: 0001104659-25-094485 · tm2527377-1_4seq1.xml · derivative · entry 1

Pisano Wayne · CIK 0001743611 · Director

10b5-1 filing: No plan indicated

Ownership: Direct

Disclosed balance after: 48,800

Underlying: Common Stock, par value $0.0001 · 48,800 shares

Expires 2035-09-25

F1 · derivative.exercise_date: The shares underlying the option become vested and exercisable in substantially equal monthly installments over the 12 months following September 25, 2025, subject to the reporting person's continued service through the applicable vesting date.

SEC source: 0001104659-25-094493 · tm2527377-5_4seq1.xml · derivative · entry 2

GILL JOHN · CIK 0001409939 · Director

10b5-1 filing: No plan indicated

Ownership: Direct

Disclosed balance after: 48,800

Underlying: Common Stock, par value $0.0001 · 48,800 shares

Expires 2035-09-25

F3 · derivative.exercise_date: The shares underlying the option become vested and exercisable in substantially equal monthly installments over the 12 months following September 25, 2025, subject to the reporting person's continued service through the applicable vesting date.

SEC source: 0001104659-25-094503 · tm2527377-9_4seq1.xml · derivative · entry 1

Sohn Catherine A. · CIK 0001555132 · Director

10b5-1 filing: No plan indicated

Ownership: Direct

Disclosed balance after: 48,800

Underlying: Common Stock, par value $0.0001 · 48,800 shares

Expires 2035-09-25

F1 · derivative.exercise_date: The shares underlying the option become vested and exercisable in substantially equal monthly installments over the 12 months following September 25, 2025, subject to the reporting person's continued service through the applicable vesting date.

SEC source: 0001104659-25-094499 · tm2527377-8_4seq1.xml · derivative · entry 1

Durso Jerome Benedict · CIK 0001698665 · Director

10b5-1 filing: No plan indicated

Ownership: Direct

Disclosed balance after: 48,800

Underlying: Common Stock, par value $0.0001 · 48,800 shares

Expires 2035-09-25

F1 · derivative.exercise_date: The shares underlying the option become vested and exercisable in substantially equal monthly installments over the 12 months following September 25, 2025, subject to the reporting person's continued service through the applicable vesting date.

SEC source: 0001104659-25-094497 · tm2527377-7_4seq1.xml · derivative · entry 1

Lawver Teri L · CIK 0001960596 · Director

10b5-1 filing: No plan indicated

Ownership: Direct

Disclosed balance after: 48,800

Underlying: Common Stock, par value $0.0001 · 48,800 shares

Expires 2035-09-25

F1 · derivative.exercise_date: The shares underlying the option become vested and exercisable in substantially equal monthly installments over the 12 months following September 25, 2025, subject to the reporting person's continued service through the applicable vesting date.

SEC source: 0001104659-25-094495 · tm2527377-6_4seq1.xml · derivative · entry 1

Jorkasky Diane · CIK 0001527204 · Director

10b5-1 filing: No plan indicated

Ownership: Direct

Disclosed balance after: 48,800

Underlying: Common Stock, par value $0.0001 · 48,800 shares

Expires 2035-09-25

F1 · derivative.exercise_date: The shares underlying the option become vested and exercisable in substantially equal monthly installments over the 12 months following September 25, 2025, subject to the reporting person's continued service through the applicable vesting date.

SEC source: 0001104659-25-094490 · tm2527377-4_4seq1.xml · derivative · entry 1

Schafer Klaus · CIK 0001705904 · Director

10b5-1 filing: No plan indicated

Ownership: Direct

Disclosed balance after: 48,800

Underlying: Common Stock, par value $0.0001 · 48,800 shares

Expires 2035-09-25

F1 · derivative.exercise_date: The shares underlying the option become vested and exercisable in substantially equal monthly installments over the 12 months following September 25, 2025, subject to the reporting person's continued service through the applicable vesting date.

SEC source: 0001104659-25-094488 · tm2527377-3_4seq1.xml · derivative · entry 1

SAYARE MITCHEL · CIK 0001201196 · Director

10b5-1 filing: No plan indicated

Ownership: Direct

Disclosed balance after: 48,800

Underlying: Common Stock, par value $0.0001 · 48,800 shares

Expires 2035-09-25

F1 · derivative.exercise_date: The shares underlying the option become vested and exercisable in substantially equal monthly installments over the 12 months following September 25, 2025, subject to the reporting person's continued service through the applicable vesting date.

SEC source: 0001104659-25-094487 · tm2527377-2_4seq1.xml · derivative · entry 1

Hodges Philip · CIK 0001705562 · Director

10b5-1 filing: No plan indicated

Ownership: Direct

Disclosed balance after: 48,800

Underlying: Common Stock, par value $0.0001 · 48,800 shares

Expires 2035-09-25

F1 · derivative.exercise_date: The shares underlying the option become vested and exercisable in substantially equal monthly installments over the 12 months following September 25, 2025, subject to the reporting person's continued service through the applicable vesting date.

SEC source: 0001104659-25-090867 · tm2526275-2_4seq1.xml · derivative · entry 2

Richardson Linda M · CIK 0001595064 · Chief Commercial Officer

10b5-1 filing: No plan indicated

Ownership: Direct

Disclosed balance after: 96,000

Underlying: Common Stock, par value $0.0001 · 96,000 shares

Expires not disclosed

F2 · derivative.exercise_price: Each Restricted Stock Unit ("RSU") represents a contingent right to receive one share of Common Stock, par value $0.0001, when vested

F3 · derivative.exercise_date: The RSUs become vested over four (4) years with 25% of the shares vesting 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.

F3 · derivative.expiration_date: The RSUs become vested over four (4) years with 25% of the shares vesting 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.

SEC source: 0001104659-25-090867 · tm2526275-2_4seq1.xml · derivative · entry 1

Richardson Linda M · CIK 0001595064 · Chief Commercial Officer

10b5-1 filing: No plan indicated

Ownership: Direct

Disclosed balance after: 278,000

Underlying: Common Stock, par value $0.0001 · 278,000 shares

Expires 2035-09-16

F1 · derivative.exercise_date: The shares underlying the option become vested and exercisable over four (4) years with 25% of the shares vesting on September 16, 2026, with the remainder vesting in equal monthly installments for the following thirty-six (36) months, subject to the reporting person's continued service on each applicable vesting date.

SEC source: 0001104659-25-073629 · tm2522384-3_4seq1.xml · nonDerivative · entry 1

Jordt Raymond M · CIK 0001960780 · Chief Business Officer

10b5-1 filing: No plan indicated

Ownership: Direct

Disclosed balance after: 36,270

F1 · kind: These shares were purchased due to participation by the reporting individual in the Issuer's 2019 Employee Stock Purchase Plan ("ESPP"). It pertains to the ESPP purchase period from February 1, 2025 through July 31, 2025.

F2 · price: In accordance with the ESPP, these shares were purchased based on 85% of the closing price of the issuer's common stock on July 31, 2025.

SEC source: 0001104659-25-073627 · tm2522384-2_4seq1.xml · nonDerivative · entry 1

Harris Matthew Scott · CIK 0001787762 · Chief Medical Officer

10b5-1 filing: No plan indicated

Ownership: Direct

Disclosed balance after: 16,087

F1 · kind: These shares were purchased due to participation of the reporting individual in the Issuer's 2019 Employee Stock Purchase Plan ("ESPP"). It pertains to the ESPP purchase period from February 1, 2025 through July 31, 2025.

F2 · price: In accordance with the ESPP, these shares were purchased based on 85% of the closing price of the issuer's common stock.

SEC source: 0001104659-25-073624 · tm2522384-1_4seq1.xml · nonDerivative · entry 1

Roberts M Scot · CIK 0001705905 · Chief Scientific Officer

10b5-1 filing: No plan indicated

Ownership: Direct

Disclosed balance after: 74,066

F1 · kind: These shares were purchased due to participation by the reporting individual in the Issuer's 2019 Employee Stock Purchase Plan ("ESPP"). It pertains to the ESPP purchase period from February 1, 2025 through July 31, 2025.

F2 · price: In accordance with the ESPP, these shares were purchased based on 85% of the closing price of the issuer's common stock on July 31, 2025.

SEC source: 0001104659-25-025032 · tm259651-1_4seq1.xml · nonDerivative · entry 1

Sohn Catherine A. · CIK 0001555132 · Director

10b5-1 filing: No plan indicated

Ownership: Direct

Disclosed balance after: 1,000

SEC source: 0001104659-25-023724 · tm259169-1_4seq1.xml · nonDerivative · entry 1

WEAVER GREGORY L · CIK 0001251779 · Chief Financial Officer

10b5-1 filing: No plan indicated

Ownership: Direct

Disclosed balance after: 10,000

F1 · price: The price reported in Column 4 is a weighted average price. These shares were purchased in multiple transactions at prices ranging from $5.1950 to $5.1997, inclusive. The reporting person undertakes to provide to Altimmune, Inc., any security holder of Altimmune, Inc., or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares purchased at each separate price within the ranges set forth in this footnote.

SEC source: 0001104659-25-022550 · tm258873-1_4seq1.xml · nonDerivative · entry 1

Harris Matthew Scott · CIK 0001787762 · Chief Medical Officer

10b5-1 filing: No plan indicated

Ownership: Direct

Disclosed balance after: 14,069

F1 · ownership.direct: On March 7, 2025, the reporting person transferred 67,787 shares of common stock to the Matthew Scott Harris Trust for no consideration. The reporting person is trustee of the trust, and the reporting person and members of his immediate family are the sole beneficiaries of the trust. The reporting person remains the beneficial owner of the securities held by the trust.

SEC source: 0001104659-25-017006 · tm257585-3_4seq1.xml · derivative · entry 1

Durso Jerome Benedict · CIK 0001698665 · Director

10b5-1 filing: No plan indicated

Ownership: Direct

Disclosed balance after: 69,800

Underlying: Common Stock, par value $0.0001 · 69,800 shares

Expires 2035-02-24

F1 · derivative.exercise_date: The shares underlying the option become vested and exercisable in 36 substantially equal monthly installments following February 24, 2025 subject to the reporting person's continued service through the applicable vesting date.

SEC source: 0001104659-25-017580 · tm257585-4_4seq1.xml · derivative · entry 1

Lawver Teri L · CIK 0001960596 · Director

10b5-1 filing: No plan indicated

Ownership: Direct

Disclosed balance after: 69,800

Underlying: Common Stock, par value $0.0001 · 69,800 shares

Expires 2035-02-24

F1 · derivative.exercise_date: The shares underlying the option become vested and exercisable in 36 substantially equal monthly installments following February 24, 2025 subject to the reporting person's continued service through the applicable vesting date.

SEC source: 0001104659-25-010528 · tm255923-1_4seq1.xml · derivative · entry 1

Sohn Catherine A. · CIK 0001555132 · Director

10b5-1 filing: No plan indicated

Ownership: Direct

Disclosed balance after: 18,600

Underlying: Common Stock, par value $0.0001 · 18,600 shares

Expires 2035-02-06

F1 · derivative.exercise_date: The shares underlying the option shall vest as follows: (i) 50% on July 15, 2025, (ii) 25% on September 30, 2025 and 25% on December 31, 2025, subject to the reporting person's continued service through the applicable vesting date.

SEC source: 0001104659-25-008772 · tm255357-3_4seq1.xml · derivative · entry 10

Harris Matthew Scott · CIK 0001787762 · Chief Medical Officer

10b5-1 filing: No plan indicated

Ownership: Direct

Disclosed balance after: 7,775

Underlying: Common Stock, par value $0.0001 · 7,775 shares

Expires not disclosed

Exercise/conversion can include RSU settlement. Transaction price and option strike are different fields; a missing price is not zero. Derivative and underlying rows can describe the same event.

F1 · derivative.exercise_price: Each Restricted Stock Unit ("RSU") represents a contingent right to receive one share of Common Stock, par value $0.0001, when vested.

F7 · derivative.exercise_date: The RSUs vest in substantially equal annual installments over the 4 years following February 2, 2022, subject to the reporting person's continued service through the applicable vesting date, and have no expiration date.

F7 · derivative.expiration_date: The RSUs vest in substantially equal annual installments over the 4 years following February 2, 2022, subject to the reporting person's continued service through the applicable vesting date, and have no expiration date.

SEC source: 0001104659-25-008772 · tm255357-3_4seq1.xml · nonDerivative · entry 7

Harris Matthew Scott · CIK 0001787762 · Chief Medical Officer

10b5-1 filing: No plan indicated

Ownership: Direct

Disclosed balance after: 81,856

F1 · kind: Each Restricted Stock Unit ("RSU") represents a contingent right to receive one share of Common Stock, par value $0.0001, when vested.