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.  ☐

Note: Schedules filed in paper format shall include a signed original and five copies of the schedule, including all exhibits. See §240.13d-7 for other parties to whom copies are to be sent.

* The remainder of this cover page shall be filled out for a reporting person’s initial filing on this form with respect to the subject class of securities, and for any subsequent amendment containing information which would alter disclosures provided in a prior cover page.

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).

CUSIP No. P8696W104

(1) Based on 69,081,861 Common Shares outstanding, consisting of (i) 57,281,861 shares outstanding as of December 31, 2017, as reported in the Issuer’s Form 20-F filed with the Securities and Exchange Commission on May 11, 2018 and (ii) 11,800,000 shares issued in a private placement by the Issuer on July 2, 2018.

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SCHEDULE 13D

This statement on Schedule 13D relates to the Common Shares, par value $0.001 per share (the “Common Shares”) of Sinovac Biotech Ltd., an Antigua and Barbuda company (the “Issuer”). The address of the principal executive offices of the Issuer is No. 15 Zhi Tong Road, Zhongguancun Science and Technology Park, Changping District, Beijing 102200, People’s Republic of China.

On July 2, 2018, the Issuer entered into a Securities Purchase Agreement (the “Purchase Agreement”) with Vivo Capital, LLC and Prime Success, L.P. (each an “Investor” and together, the “Investors”), pursuant to which the Issuer, in a private placement (the “Private Placement”), issued and sold to the Investors an aggregate of 11,800,000 Common Shares (the “Shares”) for an aggregate purchase price of $86,730,000, or $7.35 per Share. The Purchase Agreement is Exhibit A to this Schedule 13D and is incorporated herein by reference to Exhibit 99.2 to the Issuer’s Report on Form 6-K filed with the Securities and Exchange Commission on July 3, 2018 (the “Form 6-K”). Any description of the Purchase Agreement is qualified in its entirety by reference thereto. Pursuant to the Purchase Agreement, Vivo purchased 5,900,000 Shares for a purchase price of $43,365,000. Vivo issued a Promissory Note dated July 2, 2018 (the “Promissory Note”), pursuant to which it promised to pay such purchase price, plus all interest accrued thereon, to the Issuer. The Promissory Note is Exhibit B to this Schedule 13D and is incorporated herein by reference to Exhibit 99.5 to the Form 6-K. Any description of the Promissory Note is qualified in its entirety by reference thereto.

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Vivo purchased the Shares for investment purposes. Vivo intends to transfer such Shares to one or more funds managed by Vivo.

In connection with the Purchase Agreement and the Private Placement, the Issuer entered into a Shareholders Agreement with the Investors (the “Shareholders Agreement”). The Shareholders Agreement is Exhibit C to this Schedule 13D and is incorporated herein by reference to Exhibit 99.4 to the Form 6-K. Any description of the Shareholders Agreement is qualified in its entirety by reference thereto. Pursuant to the Shareholders Agreement, Vivo has the right to designate one individual to be elected to the Issuer’s Board of Directors.

Except as otherwise described in this statement, the Reporting Person does not have any present plans or proposals that relate to or would result in: (i) the acquisition by any person of additional securities of the Issuer, or the disposition of securities of the Issuer; (ii) an extraordinary corporate transaction, such as a merger, reorganization or liquidation, involving the Issuer or any of its subsidiaries; (iii) a sale or transfer of a material amount of assets of the Issuer or any of its subsidiaries; (iv) any change in the present Board of Directors or management of the Issuer, including any plans or proposals to change the number or term of directors or to fill any existing vacancies on the board; (v) any material change in the present capitalization or dividend policy of the Issuer; (vi) any other material change in the Issuer’s business or corporate structure; (vii) changes in the Issuer’s charter, by-laws or instruments corresponding thereto or other actions which may impede the acquisition of control of the Issuer by any person; (viii) causing a class of securities of the Issuer to be de-listed from a national securities exchange or to cease to be authorized to be quoted in an inter-dealer quotation system of a registered national securities association; (ix) a class of equity securities of the Issuer becoming eligible for termination of registration pursuant to Section 12(g)(4) of the Exchange Act; or (x) any action similar to any of those enumerated above. The Reporting Person may change its present intentions at any time and therefore reserves the right to make alternative plans or proposals in the future or take any other steps to enhance the value of its investment. The Reporting Person may, from time to time, depending on market conditions and other considerations, acquire additional securities of the Issuer or dispose of some or all of the securities of the Issuer held by it, as permitted by the relevant securities laws and any agreement or agreements that have been or may be entered into with the Issuer. In addition, the Reporting Person and its representatives and advisers may, from time to time, engage in discussions with the Issuer’s Board of Directors, management, other shareholders, industry participants and/or other interested parties concerning the Issuer.

Based on the transactions described herein, including the Shareholders Agreement, the Reporting Person may be deemed to constitute a “group” with Prime Success L.P. within the meaning of Section 13(d)(3) of the Act. Members of a group may be deemed to beneficially own the securities beneficially owned by other members of the group. However, the Reporting Person expressly disclaims any beneficial ownership in the securities held by Prime Success L.P., or by any of its affiliates. The filing of this Statement shall not be construed as an admission that the Reporting Person and its affiliates, on the one hand, and Prime Success L.P. and its 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.

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In connection with the Purchase Agreement and the Private Placement, the Issuer entered into a Registration Rights Agreement with the Investors (the “Registration Rights Agreement”). The Registration Rights Agreement is Exhibit D to this Schedule 13D and is incorporated herein by reference to Exhibit 99.3 to the Form 6-K. Any description of the Registration Rights Agreement is qualified in its entirety by reference thereto. Pursuant to the Registration Rights Agreement the Issuer granted certain registration and other rights under the Securities Act of 1933, as amended, with respect to the Registrable Securities (as defined therein), including the Shares.

Exhibit A - Purchase Agreement (incorporated by reference to Exhibit 99.2 to the Issuer’s Report on Form 6-K filed with the Securities and Exchange Commission on July 3, 2018)

Exhibit B – Promissory Note (incorporated by reference to Exhibit 99.5 to the Issuer’s Report on Form 6-K filed with the Securities and Exchange Commission on July 3, 2018)

Exhibit C – Shareholders Agreement (incorporated by reference to Exhibit 99.4 to the Issuer’s Report on Form 6-K filed with the Securities and Exchange Commission on July 3, 2018)

Exhibit D – Registration Rights Agreement (incorporated by reference to Exhibit 99.3 to the Issuer’s Report on Form 6-K filed with the Securities and Exchange Commission on July 3, 2018)

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SIGNATURE

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

Dated: July 11, 2018