# EDGAR Filing Document

**Accession Number:** 0001264738
**File Stem:** 0001104659-25-067910
**Filing Date:** 2025-7
**Character Count:** 7867
**Document Hash:** e6e50f9303c4ff96a18e64739cb0af50
**Contains OCR:** False
**Source Format:** 

## Filing Content

## Filing Summary
**0001104659-25-067910.hdr.sgml**: 20250715

**ACCESSION NUMBER**: 0001104659-25-067910

**CONFORMED SUBMISSION TYPE**: SCHEDULE 13D/A

**PUBLIC DOCUMENT COUNT**: 1

**FILED AS OF DATE**: 20250715

**DATE AS OF CHANGE**: 20250715

**SUBJECT COMPANY**: 

**COMPANY DATA:**
- **COMPANY CONFORMED NAME:** SINOVAC BIOTECH LTD
- **CENTRAL INDEX KEY:** 0001084201
- **STANDARD INDUSTRIAL CLASSIFICATION:** PHARMACEUTICAL PREPARATIONS [2834]
- **ORGANIZATION NAME:** 03 Life Sciences
- **EIN:** 000000000
- **STATE OF INCORPORATION:** B9
- **FISCAL YEAR END:** 1231

**FILING VALUES:**
- **FORM TYPE:** SCHEDULE 13D/A
- **SEC ACT:** 1934 Act
- **SEC FILE NUMBER:** 005-79318
- **FILM NUMBER:** 251123030

**BUSINESS ADDRESS:**
- **STREET 1:** NO. 39 SHANGDI XI ROAD
- **STREET 2:** HAIDIAN DISTRICT
- **CITY:** BEIJING
- **STATE:** F4
- **ZIP:** 100085
- **BUSINESS PHONE:** 86-10-82890088

**MAIL ADDRESS:**
- **STREET 1:** NO. 39 SHANGDI XI ROAD
- **STREET 2:** HAIDIAN DISTRICT
- **CITY:** BEIJING
- **STATE:** F4
- **ZIP:** 100085

**FORMER COMPANY:**
- **FORMER CONFORMED NAME:** NET FORCE SYSTEMS INC
- **DATE OF NAME CHANGE:** 19991110
**FILED BY**: 

**COMPANY DATA:**
- **COMPANY CONFORMED NAME:** WEIDONG YIN
- **CENTRAL INDEX KEY:** 0001264738

**ORGANIZATION NAME:**

**FILING VALUES:**
- **FORM TYPE:** SCHEDULE 13D/A

**MAIL ADDRESS:**
- **STREET 1:** LATHAM& WATKINS
- **STREET 2:** 200 CLARENDON STREET
- **CITY:** BOSTON
- **STATE:** MA
- **ZIP:** 02116

### UNITED STATES SECURITIES AND EXCHANGE COMMISSION
**Washington, D.C. 20549**

## SCHEDULE 13D

### Under the Securities Exchange Act of 1934

**(Amendment No. 6)**

**SINOVAC BIOTECH LTD.**

*(Name of Issuer)*

**Common Shares**

*(Title of Class of Securities)*

**P8696W104**

*(CUSIP Number)*

**Weidong Yin**<br>No. 39 Shangdi Xi Road<br>Haidian District<br>Beijing F4 100085<br>86-10-8289-0088

*(Name, Address and Telephone Number of Person Authorized to Receive Notices and Communications)*

**07/10/2025**

*(Date of Event Which Requires Filing of this Statement)*

| **CUSIP No.** | **P8696W104** |

---

| | | | |
|:--|:--|:--|:--|
| 1 | Name of reporting person<br>**Weidong Yin** | Name of reporting person<br>**Weidong Yin** | |
| 2 | Check the appropriate box if a member of a Group (See Instructions)<br>[ ] (a)<br>[x] (b) | Check the appropriate box if a member of a Group (See Instructions)<br>[ ] (a)<br>[x] (b) | |
| 3 | SEC use only | SEC use only | |
| 4 | Source of funds (See Instructions)<br>**PF** | Source of funds (See Instructions)<br>**PF** | |
| 5 | Check if disclosure of legal proceedings is required pursuant to Items 2(d) or 2(e)<br>[ ] | Check if disclosure of legal proceedings is required pursuant to Items 2(d) or 2(e)<br>[ ] | |
| 6 | Citizenship or place of organization<br>**CHINA** | Citizenship or place of organization<br>**CHINA** | |
| Number of Shares<br>Beneficially Owned by<br>Each Reporting Person With: | 7 | Sole Voting Power<br>**6359500.00** |
| Number of Shares<br>Beneficially Owned by<br>Each Reporting Person With: | 8 | Shared Voting Power<br>**0.00** |
| Number of Shares<br>Beneficially Owned by<br>Each Reporting Person With: | 9 | Sole Dispositive Power<br>**6359500.00** |
| Number of Shares<br>Beneficially Owned by<br>Each Reporting Person With: | 10 | Shared Dispositive Power<br>**0.00** |
| 11 | Aggregate amount beneficially owned by each reporting person<br>**6359500.00** | Aggregate amount beneficially owned by each reporting person<br>**6359500.00** | |
| 12 | Check if the aggregate amount in Row (11) excludes certain shares (See Instructions)<br>[ ] | Check if the aggregate amount in Row (11) excludes certain shares (See Instructions)<br>[ ] | |
| 13 | Percent of class represented by amount in Row (11)<br>**8.85%** | Percent of class represented by amount in Row (11)<br>**8.85%** | |
| 14 | Type of Reporting Person (See Instructions)<br>**IN** | Type of Reporting Person (See Instructions)<br>**IN** | |

---

**Comment for Reporting Person:** Comments to item 13: Calculation is 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").

**Item 1. Security and Issuer**

**(a) Title of Class of Securities:**
Common Shares

**(b) Name of Issuer:**
SINOVAC BIOTECH LTD.

**(c) Address of Issuer's Principal Executive Offices:**
No. 39 Shangdi Xi Rd, Haidian District, Beijing, F4, 100085

This Amendment No.6 to Schedule 13D is being filed on behalf of Weidong Yin (the "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 Person on February 7, 2008, as amended by Amendment No.1 to Schedule 13D filed on February 8, 2016, Amendment No.2 to Schedule 13D filed on June 27, 2017, Amendment No.3 to Schedule 13D filed on March 21, 2025, Amendment No.4 to Schedule 13D filed on April 30, 2025 and Amendment No.5 to Schedule 13D filed on June 20, 2025 (collectively, the "Original Schedule 13D"). The information in each Item below amends the information disclosed under the corresponding Item of the Original Schedule 13D. Except as amended and supplemented herein, the information set forth in the Original Schedule 13D remains unchanged. Capitalized terms used herein have meanings as assigned thereto in the Original Schedule 13D unless defined herein. The information set forth in response to each separate Item below shall be deemed to be a response to all Items where such information is relevant.

**Item 4. Purpose of Transaction**

Item 4 is hereby amended and supplemented to add the following:

The Issuer announced on July 10, 2025 a new board of directors of the Issuer (the "Board"), comprising Mr. Simon Anderson, Mr. Shan Fu, Mr. Shuge Jiao, Mr. Chiang Li, Mr. Yuk Lam Lo, Mr. Yumin Qiu, Mr. Yu Wang, Ms. Rui-Ping Xiao, Mr. Andrew Y Yan (as Chairman of the Board) and the Reporting Person. The Reporting Person has accepted the appointment and plans to participate in the future governance of the Issuer as a member of the newly Board.

Except as set forth in this Item 4, the Reporting Person has no present plan or intention that wouldresu lt in or relate to the listed transactions described in Item 4 of Schedule 13D. The Reporting Person has engaged and will continue to engage in discussions with other shareholders of the Issuer regarding the Board, the corporate governance and similar matters that the Reporting Person believes would increase shareholder value, and depending on the outcome of the discussion, the Reporting Person may pursue plans or proposals that relate to or would result in any of the matters set forth in clauses (a)-(j) of Item 4 of Schedule 13D.

The filing of this Amendment shall not be construed as an admission that the Reporting Person, 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 Person expressly disclaims beneficial ownership of the common shares beneficially owned by other shareholders of the Issuer.

**Item 6. Contracts, Arrangements, Understandings or Relationships With Respect to Securities of the Issuer.**

Item 6 is hereby amended and supplemented to add the following:

Item 4 of Amendment No. 6 is incorporated herein by reference.

### SIGNATURE

After reasonable inquiry and to the best of my knowledge and belief, I certify that the information set forth in this statement is true, complete and correct.

**Reporting Person:** Weidong Yin

**Signature:** /s/ Weidong Yin

**Name/Title:** Weidong Yin

**Date:** 07/14/2025