[SCHEDULE 13D/A] Sinovac Biotech, Ltd SEC Filing

Rhea-AI Filing Summary

Schedule 13D/A Amendment No. 5 – Sinovac Biotech Ltd. (SVA)

The filing, dated 19 June 2025 and triggered by events on 16 June 2025, updates the ownership position of Weidong Yin, a long-time insider and former executive of Sinovac. Yin reports sole voting and dispositive power over 6,359,500 common shares, representing 8.85 % of the 71,860,702 shares outstanding cited in the company’s FY-2023 Form 20-F. No shares are held jointly and no derivatives or other economic interests are disclosed, indicating a straightforward equity stake funded with personal funds ("PF").

New governance development (Item 4): On 17 June 2025, shareholder SAIF Partners IV L.P. mailed definitive proxy materials for a special meeting on 8 July 2025 (9 July 2025 CST), proposing, among other matters, to nominate several directors, including Yin, to Sinovac’s board. Yin confirms preliminary discussions with SAIF but states no agreement on cooperation or voting arrangements has been reached. He reserves the right to engage in additional discussions or pursue future actions that could involve any of the matters listed under Item 4(a)-(j) of Regulation 13D.

No other material changes: Items concerning intent, contracts, and litigation remain unchanged from previous amendments, apart from incorporating the above governance disclosure by reference. The filing does not modify Yin’s economic exposure or signal additional share purchases or sales.

For investors, the amendment highlights a potential alignment (or tension) between two significant shareholders ahead of a contested board election, while confirming that Yin’s 8.85 % stake remains intact.

Positive

• Stable insider holding: Weidong Yin confirms continued sole control of 6.36 million shares (8.85 % of float), signalling ongoing commitment.

Negative

• Proxy contest risk: SAIF’s solicitation and lack of agreement with Yin introduce governance uncertainty that could distract management and pressure the share price.

Insights

Corporate Governance Expert

TL;DR: Filing flags possible proxy contest; Yin holds 8.85 % and may join board, but no pact with SAIF yet—governance direction uncertain.

The amendment is narrowly focused on Item 4. Yin’s ownership is unchanged, but SAIF’s proxy solicitation moves Sinovac toward a shareholder vote that could reshape the board. Yin’s inclusion on SAIF’s slate suggests he is acceptable to an activist fund, yet the absence of a voting agreement signals independent positioning and lowers the likelihood of a formal control group under Section 13(d). From a governance standpoint, investors should watch for: 1) whether Yin publicly supports SAIF, 2) how incumbent directors respond, and 3) any settlement to avoid a full proxy fight. While the filing itself is neutral economically, the emerging activism could influence strategy, capital allocation, and ADR liquidity.

Portfolio Manager

TL;DR: Ownership static; looming board contest may introduce short-term volatility but no immediate valuation trigger.

The unchanged 8.85 % stake means no dilution or insider buying that directly affects intrinsic value. However, governance shifts can move sentiment—especially for a China-based biotech with a checkered control history. A successful SAIF slate, with Yin aboard, could lead to clearer strategic direction or unlock corporate actions (e.g., spin-offs, buybacks). Conversely, a deadlock might prolong uncertainty and weigh on discount rates applied to Chinese ADRs. Absent financial metrics or operational updates, I classify the filing as informational rather than catalytic, maintaining a neutral impact on near-term price targets.

SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

SCHEDULE 13D

Under the Securities Exchange Act of 1934

(Amendment No. 5)

SINOVAC BIOTECH LTD.

(Name of Issuer)

Common Shares

(Title of Class of Securities)

P8696W104

(CUSIP Number)

Weidong Yin
No. 39 Shangdi Xi Road, Haidian District
Beijing, F4, 100085
86-10-8289-0088

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

06/16/2025

(Date of Event Which Requires Filing of This Statement)

If the filing person has previously filed a statement on Schedule 13G to report the acquisition that is the subject of this Schedule 13D, and is filing this schedule because of §§ 240.13d-1(e), 240.13d-1(f) or 240.13d-1(g), check the following box.

The information required on the remainder of this cover page shall not be deemed to be "filed" for the purpose of Section 18 of the Securities Exchange Act of 1934 ("Act") or otherwise subject to the liabilities of that section of the Act but shall be subject to all other provisions of the Act (however, see the Notes).

SCHEDULE 13D

CUSIP No. P8696W104

1

Name of reporting person

Weidong Yin

2

Check the appropriate box if a member of a Group (See Instructions)

(a)
(b)

3

SEC use only

4

Source of funds (See Instructions)

PF

5

Check if disclosure of legal proceedings is required pursuant to Items 2(d) or 2(e)

6

Citizenship or place of organization

CHINA

Number of Shares Beneficially Owned by Each Reporting Person With:

7	Sole Voting Power 6,359,500.00
8	Shared Voting Power 0.00
9	Sole Dispositive Power 6,359,500.00
10	Shared Dispositive Power 0.00

11

Aggregate amount beneficially owned by each reporting person

6,359,500.00

12

Check if the aggregate amount in Row (11) excludes certain shares (See Instructions)

13

Percent of class represented by amount in Row (11)

8.85 %

14

Type of Reporting Person (See Instructions)

IN

Comment for Type of 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").

SCHEDULE 13D

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, CHINA , 100085.
Item 1 Comment: This Amendment No.5 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, and Amendment No.4 to Schedule 13D filed on April 30, 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: On June 17, 2025, SAIF Partners IV L.P. ("SAIF") filed an amendment to its Schedule 13D, announcing that it has mailed its definitive proxy materials to shareholders of the Issuer, in connection with the special meeting of shareholders of the Issuer to be held on Tuesday, July 8, 2025 at 8 p.m. Atlantic Standard Time (Wednesday, July 9, 2025 at 8:00 a.m. China Standard Time) for the purposes of, among other things, nominating a few persons, including the Reporting Person, to the board of directors of the Company (the "Board"). Before the definitive proxy materials were mailed, SAIF discussed with the Reporting Person the proposal to nominate the Reporting Person to the Board. The Reporting Person and SAIF have not reached any agreement on cooperation or voting. Except as set forth in this statement, the Reporting Person has no present plan or intention which would result in or relate to any of the transactions described in clauses (a) through (j) of Item 4 of Schedule 13D. The Reporting Person anticipates that further communications may occur with SAIF and other shareholders regarding the proxy materials and the special meeting. Depending upon, among other things, the outcome of these communications, the financial condition, results of operations and prospects of the Issuer, conditions in the securities markets, general economic conditions and other factors that the Reporting Person deem relevant, the Reporting Person 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.
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. 5 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.

Weidong Yin

Signature:	/s/ Weidong Yin
Name/Title:	Weidong Yin
Date:	06/19/2025

FAQ

How many Sinovac (SVA) shares does Weidong Yin currently own?

He reports beneficial ownership of 6,359,500 common shares, equal to 8.85 % of shares outstanding.

Why was Schedule 13D/A Amendment No. 5 filed?

It discloses SAIF’s proxy solicitation naming Yin as a board nominee and clarifies that Yin has no cooperation agreement with SAIF.

When is Sinovac’s special shareholder meeting?

The meeting is scheduled for 8 July 2025, 8 p.m. AST (9 July 2025, 8 a.m. CST).

Does the filing indicate any new share purchases or sales by Yin?

No. The amendment shows no change in Yin’s share count or percentage ownership since the prior filing.

What potential impact could the proxy vote have on Sinovac’s governance?

If SAIF’s slate succeeds, it could alter board composition and influence strategic decisions; failure may leave governance unchanged.