SCHEDULE 13D/A 0001650757 XXXXXXXX LIVE 1 Common Shares 04/09/2025 true 0001084201 P8696W104 SINOVAC BIOTECH LTD.

No. 39 Shangdi Xi Road, Haidian District Beijing F4 100085

Xingluo Zhu 86-10-8593-5676 Suite 1707-08, 17/F, One Exchange Square 8 Connaught Place, Central Hong Kong K3 000000 0001650757 N Advantech Capital L.P. b WC N E9 0.00 5851423.00 0.00 5851423.00 5851423.00 N 8.14 PN Comments to item 13: Based on 71,860,702 Common Shares of the Issuer outstanding as of March 31, 2024 according to the Issuer's annual report on Form 20-F for the fiscal year ended December 31, 2023 (the "2023 Annual Report"). Y Advantech Capital Partners Ltd. b WC N E9 0.00 5851423.00 0.00 5851423.00 5851423.00 N 8.14 CO Comments to item 13: Based on 71,860,702 Common Shares of the Issuer outstanding as of March 31, 2024 according to the 2023 Annual Report. Y Green Vision Partners Limited b WC N E9 0.00 5851423.00 0.00 5851423.00 5851423.00 N 8.14 CO Comments to item 13: Based on 71,860,702 Common Shares of the Issuer outstanding as of March 31, 2024 according to the 2023 Annual Report. Y Prime Success, L.P. b WC N E9 0.00 5851423.00 0.00 5851423.00 5851423.00 N 8.14 PN Comments to item 13: Based on 71,860,702 Common Shares of the Issuer outstanding as of March 31, 2024 according to the 2023 Annual Report. Common Shares SINOVAC BIOTECH LTD. No. 39 Shangdi Xi Road, Haidian District Beijing F4 100085 This Amendment No.1 to Schedule 13D is being filed on behalf of Advantech Capital L.P., Advantech Capital Partners Ltd., Green Vision Partners Limited and Prime Success, L.P. (each, a "Reporting Person") to amend the Schedule 13D relating to the common shares, par value $0.001 per share (the "Common Shares"), of Sinovac Biotech Ltd. (the "Issuer"), filed by the Reporting Persons on March 25, 2025. The items herein amend the information disclosed under the corresponding items of the original Schedule 13D. Capitalized terms used herein and not otherwise defined have the meanings given to them in the original Schedule 13D. Item 4 is hereby supplemented and amended by adding the following: The Issuer's announcement on April 1, 2025 implies that the New Board will take steps to determine whether the Reporting Persons' shares in the Issuer are valid and that the Issuer will issue a cash dividend to shareholders that excludes the Reporting Persons' entitlement. The Reporting Persons intend to take all necessary action to protect their entitlement. In connection thereto, on April 9, 2025 the Reporting Persons requested to join an arbitration that Vivo Capital initiated in March 2025 against the Issuer at the Hong Kong International Arbitration Centre seeking, among other things, a declaration affirming the Reporting Persons' rights to its entitlement. The Reporting Persons may take additional actions as needed to further protect their rights and investment. Except as set forth herein as may be necessary for defending their lawful interests in the Issuer in relation to the 2018 Private Placement, either alone or in coordination with any one or more shareholders of the Issuer, the Reporting Persons have no present plan or intention that would result in or relate to any of the transactions described in clauses (a) through (j) of Item 4 of Schedule 13D. Depending on discussions with other shareholders of the Issuer, the financial condition, results of operations and prospects of the Issuer and other factors that the Reporting Persons deem relevant, the Reporting Persons may take steps and pursue other plans or proposals that relate to or would result in any of the matters set forth in clauses (a) through (j) of Item 4 of Schedule 13D. The filing of this Amendment shall not be construed as an admission that the Reporting Persons and their affiliates, on the one hand, and any other shareholders of the Issuer and their affiliates, on the other hand, are a group, or have agreed to act as a group with each other for purposes of Section 13(d) of the Act or for any other purpose. The Reporting Persons expressly disclaim beneficial ownership of the common shares beneficially owned by other shareholders of the Issuer. Item 5 is hereby amended and restated as follows: The information requested by this paragraph is incorporated herein by reference to the information provided on the cover pages to this Amendment No.1 to Schedule 13D. The information requested by this paragraph is incorporated herein by reference to the information provided on the cover pages to this Amendment No.1 to Schedule 13D. No Reporting Person has, and to the knowledge of the Reporting Persons, no Person named in Item 2 to this Amendment No.1 to Schedule 13D has, effected any other transactions in the securities of the Issuer during the past 60 days. Except as otherwise described herein, and to the knowledge of the Reporting Person, no other person has the right to receive or the power to direct the receipt of dividends from, or the proceeds from the sale of, the Common Shares owned by the Reporting Person. Not applicable. Item 6 is hereby supplemented and amended by adding the following: Item 4 of this Amendment No. 1 to Schedule 13D is incorporated herein by reference. Advantech Capital L.P. /s/ Yan Yang 04/10/2025 Advantech Capital Partners Ltd. /s/ Yan Yang 04/10/2025 Green Vision Partners Limited /s/ Yan Yang 04/10/2025 Prime Success, L.P. /s/ Yan Yang 04/10/2025