6-K

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

WASHINGTON, DC 20549

FORM 6-K

REPORT OF FOREIGN PRIVATE ISSUER

PURSUANT TO RULE 13a-16 OR 15d-16 UNDER

THE SECURITIES EXCHANGE ACT OF 1934

For the month of October 2010

Commission File Number: 001-32371

SINOVAC BIOTECH LTD.

No. 39 Shangdi Xi Road

Haidian District

Beijing 100085, People’s Republic of China

(Address of principal executive offices)

Indicate by check mark whether the registrant files or will file annual reports under cover of Form 20-F or Form 40-F:

Form 20-F x Form 40-F o

Indicate by check mark if the registrant is submitting the Form 6-K in paper as permitted by Regulation S-T Rule 101(b)(1): o

Indicate by check mark if the registrant is submitting the Form 6-K in paper as permitted by Regulation S-T Rule 101(b)(7): o

SIGNATURE

Pursuant to the requirements of the Securities Exchange Act of 1934, the registrant has duly caused this report to be signed on its behalf by the undersigned, thereunto duly authorized.

	SINOVAC BIOTECH LTD.
	By:	/s/ Weidong Yin
	Name: Weidong Yin
	Title: Chairman and Chief Executive Officer
Date: October 25, 2010

2

Exhibit Index

Exhibit 99.1 – Press Release

Exhibit 99.2 – Press Release

Exhibit 99.3 – Press Release

3

EX-99.1

Exhibit 99.1

Sinovac Announces Preliminary Unaudited Third Quarter 2010 Sales Range and Revises Full Year 2010 Sales Expectations

Press Release Source: Sinovac Biotech Ltd. On Sunday October 24, 2010, 5:00 pm

BEIJING, Oct. 24 /PRNewswire-Asia-FirstCall/ — Sinovac Biotech Ltd. (Nasdaq:SVA - News), a leading provider of biopharmaceutical products in China, announced today its preliminary unaudited sales range for the third quarter ended September 30, 2010 and revised sales guidance for full year 2010. A conference call to discuss these preliminary results and revised sales guidance will be held on October 25, 2010 at 8:00 a.m. Eastern Time (October 25, 2010 at 8:00 pm China Standard Time). The Company will issue its final unaudited 2010 third quarter and nine months financial results on or about November 15, 2010.

Sinovac expects its third quarter 2010 sales to be in the range of approximately $9 million to $10 million. The Company revises its total 2010 sales expectations to be in the range of approximately $40 million to $45 million compared to previous expectations in the range of $60 million to $67 million. The Company has provided this revised outlook based on the following factors:

1.The vaccine market in China is experiencing a much longer than originally expected demand weakness in the market following the unfounded media reports about vaccine safety in China’s Shanxi province.

2.A large-scale measles vaccination campaign was conducted in September 2010 that delayed administration of routine vaccinations, including the seasonal influenza vaccine. The campaign concluded in September 2010.

Sinovac vaccine product portfolio is comprised of five commercialized products and a number of pipeline products. The Company is advancing the development of its portfolio and pursuing opportunities to add products. Currently the R&D process for our pipeline products is progressing well on schedule.

Dr. Weidong Yin, Chairman, President and CEO of Sinovac, stated, “We are well positioned to leverage our competitive strengths as we deliver mid to long term growth to our shareholders. We have proven research and development capabilities and a robust vaccine development pipeline with promising market potential. With stringent quality assurance programs in place at our manufacturing facilities, we are poised to benefit from new China GMP standards that are anticipated to be issued in the coming year. We are on track with our capacity expansion initiatives in advance of the commercialization of our pipeline products. Moreover, we are actively seeking international collaborations and potential expansion opportunities.”

The preliminary sales range is a preliminary unaudited estimate for the quarter ended September 30, 2010. The Company’s financial results for third quarter of 2010 have not been finalized, and remain subject to the completion of its normal quarter-end closing procedures and possible change.

Conference Call Details

The Company will host a conference call on Monday, October 25, 2010 at 8:00 a.m. EDT (October 25, 2010 at 8:00 pm China Standard Time) to review the Company’s selected preliminary unaudited sales range for the third quarter ended September 30, 2010 and revised full year 2010 sales expectations. To access the conference call, please dial 1-877-407-4018 (USA) or 1-201-689-8471 (international). A replay of the call will be available from 11:00 a.m. EDT on October 25, 2010 to November 8, 2010 at midnight. To access the replay, please dial 1-877-870-5176 (USA) or 1-858-384-5517 (international) and the replay pin number 359546.

A live audio webcast of the call will also be available from the Investors section on the corporate web site at http://www.sinovac.com. A webcast replay can be accessed on the corporate website beginning October 25, 2010 and the replay will remain available for 30 days.

About Sinovac

Sinovac Biotech Ltd. is a China-based biopharmaceutical company that focuses on the research, development, manufacture and commercialization of vaccines that protect against human infectious diseases including hepatitis A, seasonal influenza, H5N1 (bird flu) pandemic influenza and H1N1 influenza. In 2009, Sinovac was the first company worldwide to receive approval for its H1N1 influenza vaccine, PANFLU.1 and has received the orders from the Chinese Central Government pursuit to the government stockpiling program. The company is currently developing a number of new vaccine products, including pneumococcal conjugate vaccine, EV71

inactivated vaccine (against Hand, Foot & Mouth Disease), Japanese Encephalitis vaccine, animal and human rabies vaccine, HIB and epidemic meningitis, chickenpox, mumps and rubella vaccines. Its wholly owned subsidiary, Tangshan Yian, is focusing on the research, development, manufacturing and commercialization of animal vaccines and currently has completed the field trials for an independently developed inactivated animal rabies vaccine, which is anticipated to be launched into market in 2011.

Safe Harbor Statement

This announcement contains forward-looking statements. These statements are made under the “safe harbor” provisions of the U.S. Private Securities Litigation Reform Act of 1995. These forward-looking statements can be identified by words or phrases such as “will,” “expects,” “anticipates,” “future,” “intends,” “plans,” “believes,” “estimates” and similar statements. Among other things, the business outlook and quotations from management in this press release contain forward-looking statements. Statements that are not historical facts, including statements about Sinovac’s beliefs and expectations, are forward-looking statements. Forward-looking statements involve inherent risks and uncertainties. A number of important factors could cause actual results to differ materially from those contained in any forward-looking statement. Sinovac does not undertake any obligation to update any forward-looking statement, except as required under applicable law.

For further information, please contact:

Helen Yang

Sinovac Biotech Ltd.

Tel:  +86-10-8279-9871

Fax:  +86-10-6296-6910

Email: info@sinovac.com

Investors:

Stephanie Carrington/Amy Glynn

The Ruth Group

Tel:  +1-646-536-7017/7023

Email: scarrington@theruthgroup.com

aglynn@theruthgroup.com

Media:

Jason Rando

The Ruth Group

Tel:  +1-646-536-7025

Email: jrando@theruthgroup.com

EX-99.2

Exhibit 99.2

Sinovac Selected by Beijing CDC to Supply Seasonal Flu Vaccine Anflu(R) to Beijing Citizens

Press Release Source: Sinovac Biotech Ltd. On Sunday October 24, 2010, 5:05 pm

BEIJING, Oct. 24 /PRNewswire-Asia-FirstCall/ — Sinovac Biotech Ltd. (Nasdaq:SVA - News), a leading provider of biopharmaceutical products in China, announced today that it has been selected by the Beijing Centers for Disease Control and Prevention (Beijing CDC) as one of the five manufacturers to supply seasonal influenza vaccine to the citizens of Beijing.

As part of the bidding process, the Beijing CDC evaluated potential suppliers and assigned scores for different factors, including product quality, service and price. Based on the comprehensive score, Sinovac was selected as the first priority supplier. Based on the first contract with the Beijing CDC, Sinovac will supply 375,000 doses of its seasonal influenza vaccine, Anflu®, valued at RMB 8.8 million or approximately $1.3 million. The total quantity to be supplied will depend on the actual demand in Beijing.

Dr. Weidong Yin, Chairman, President and CEO of Sinovac, stated, “Being selected as the first priority supplier of seasonal influenza vaccine by the Beijing CDC is further validation of Sinovac’s leading quality assurance system. We look forward to working closely with the Beijing CDC to deliver our Anflu vaccine to the citizens under the vaccination campaign.”

In order to prevent and control the seasonal flu, the Beijing CDC plans to provide free inoculations against the seasonal influenza to Beijing citizens, inclusive of elderly people over the age of 60 and elementary and secondary school age children. And Beijing CDC plans to order total 2.8 million doses for this vaccination campaign. Previously, school students were inoculated with the influenza vaccine at a charge of 20 RMB per person with allowances from the Bureau.

About Sinovac

Sinovac Biotech Ltd. is a China-based biopharmaceutical company that focuses on the research, development, manufacture and commercialization of vaccines that protect against human infectious diseases including hepatitis A, seasonal influenza, H5N1 (bird flu) pandemic influenza and H1N1 influenza. In 2009, Sinovac was the first company worldwide to receive approval for its H1N1 influenza vaccine, PANFLU.1, and has received orders from the Chinese Central Government pursuit to the government stockpiling program. The Company is developing a number of new vaccine products, including vaccines for pneumococcal conjugate, enterovirus 71 (EV71) (against Hand, Foot & Mouth Disease), Japanese Encephalitis, animal and human rabies, HIB and epidemic meningitis, chickenpox, mumps and rubella. Its wholly owned subsidiary, Tangshan Yian, is focusing on the research, development, manufacturing and commercialization of animal vaccines and has completed the field trials for an independently developed inactivated animal rabies vaccine, which is anticipated to be launched into market in 2011.

Safe Harbor Statement

This announcement contains forward-looking statements. These statements are made under the “safe harbor” provisions of the U.S. Private Securities Litigation Reform Act of 1995. These forward-looking statements can be identified by words or phrases such as “will,” “expects,” “anticipates,” “future,” “intends,” “plans,” “believes,” “estimates” and similar statements. Among other things, the business outlook and quotations from management in this press release contain forward-looking statements. Statements that are not historical facts, including statements about Sinovac’s beliefs and expectations, are forward-looking statements. Forward-looking statements involve inherent risks and uncertainties. A number of important factors could cause actual results to differ materially from those contained in any forward-looking statement. Sinovac does not undertake any obligation to update any forward-looking statement, except as required under applicable law.

For further information, please contact:

Helen Yang

Sinovac Biotech Ltd.

Tel:  +86-10-8279-9871

Fax:  +86-10-6296-6910

Email: info@sinovac.com

Investors:

Stephanie Carrington/Amy Glynn

The Ruth Group

Tel:  +1-646-536-7017/7023

Email: scarrington@theruthgroup.com

aglynn@theruthgroup.com

Media

Jason Rando

The Ruth Group

Tel:  +1-646-536-7025

Email: jrando@theruthgroup.com

EX-99.3

Exhibit 99.3

Sinovac Receives Drug Registration Certificate from Hong Kong Department of Health for Seasonal Flu Vaccine Anflu(R)

Press Release Source: Sinovac Biotech Ltd. On Sunday October 24, 2010, 5:10 pm

BEIJING, Oct 24 /PRNewswire-Asia-FirstCall/ — Sinovac Biotech Ltd. (Nasdaq:SVA - News), a leading provider of biopharmaceutical products in China, announced today that Sinovac Biotech (Hong Kong) Ltd., its wholly owned subsidiary company in Hong Kong, has received the Certificate of Drug/Product Registration from the Hong Kong Department of Health for its seasonal influenza vaccine Anflu®. Sinovac filed the application with the Hong Kong Department of Health for the drug registration certificate for Anflu in November 2009. Obtaining the drug certificate in Hong Kong is a continuation of Sinovac’s strategy to pursue opportunities to export its vaccines manufactured in mainland China to targeted areas and countries around the globe.

Dr. Weidong Yin, Chairman, President and CEO of Sinovac, stated, “We are advancing our international sales strategy by obtaining regulatory approvals in targeted areas and countries that will enable us generate sales by exporting our commercialized vaccines. We have successfully registered Anflu in Hong Kong and are actively evaluating marketing and distribution opportunities in this market.”

About Sinovac

Sinovac Biotech Ltd. is a China-based biopharmaceutical company that focuses on the research, development, manufacture and commercialization of vaccines that protect against human infectious diseases including hepatitis A, seasonal influenza, H5N1 (bird flu) pandemic influenza and H1N1 influenza. In 2009, Sinovac was the first company worldwide to receive approval for its H1N1 influenza vaccine, PANFLU.1, and has received the orders from the Chinese Central Government pursuit to the government stockpiling program. The Company is developing a number of new vaccine products, including vaccines for pneumococcal conjugate, enterovirus 71 (EV71) (against Hand, Foot & Mouth Disease), Japanese Encephalitis, animal and human rabies, HIB and epidemic meningitis, chickenpox, mumps and rubella. Its wholly owned subsidiary, Tangshan Yian, is focusing on the research, development, manufacturing and commercialization of animal vaccines and has completed the field trials for an independently developed inactivated animal rabies vaccine, which is anticipated to be launched into market in 2011.

Safe Harbor Statement

This announcement contains forward-looking statements. These statements are made under the “safe harbor” provisions of the U.S. Private Securities Litigation Reform Act of 1995. These forward-looking statements can be identified by words or phrases such as “will,” “expects,” “anticipates,” “future,” “intends,” “plans,” “believes,” “estimates” and similar statements. Among other things, the business outlook and quotations from management in this press release contain forward-looking statements. Statements that are not historical facts, including statements about Sinovac’s beliefs and expectations, are forward-looking statements. Forward-looking statements involve inherent risks and uncertainties. A number of important factors could cause actual results to differ materially from those contained in any forward-looking statement. Sinovac does not undertake any obligation to update any forward-looking statement, except as required under applicable law.

For further information, please contact:

Helen Yang

Sinovac Biotech Ltd.

Tel:  +86-10-8279-9871

Fax:  +86-10-6296-6910

Email: info@sinovac.com

Investors:

Stephanie Carrington/Amy Glynn

The Ruth Group

Tel:  +1-646-536-7017/7023

Email: scarrington@theruthgroup.com

aglynn@theruthgroup.com

Media

Jason Rando

The Ruth Group

Tel:  +1-646-536-7025

Email: jrando@theruthgroup.com