Exhibit 99.1

SINOVAC PROVIDES UPDATE ON CLINICAL TRIAL FOR H1N1 VACCINE TRIALS

-H1N1 Vaccine Shows Good Safety Profile-

BEIJING, Aug. 3 /PRNewswire-Asia/ -- Sinovac Biotech Ltd. (NYSE AMEX: SVA), a leading provider of vaccines in China, announced today that the clinical trial of its A/H1N1 influenza vaccine is proceeding well. All of the volunteers have received their first shot of the vaccine and, during the three-day observation of safety, the preliminary tests on the A/H1N1 influenza vaccine have indicated that the vaccine is safe and reliable in humans.

The clinical trial began on July 22, 2009 and a total of 1,614 volunteers, including 101 elders, 706 adults, 404 juvenile and 403 children, had received the first shot of the vaccine through July 25. During the three-day safety observation period, none of the volunteers participating in Sinovac's clinical tests exhibited any signs of severe adverse reactions. Total adverse event rate is 11.8%, which is similar to seasonal influenza vaccine. The adverse events were all mild and transient. The most common symptom is pain at the site of injection.

This clinical trial is organized by China's Center for Disease Control (CDC), and undertaken by Beijing CDC. The Ministry of Health (MOH) and State Food and Drug Administration (SFDA) are paying great attention to this clinical trial. Deputy Director General of MOH Disease Control Department, Donglou Xiao, Director of SFDA Registration Section, Wei Zhang, and other relevant experts visited the clinical site to inspect the clinical study. In June 2009, Sinovac announced that the Ministry of Health had made an initial order of 4 million doses of Panflu, which is expected to be delivered by the end of September.

As usual, Sinovac's seasonal influenza vaccine has been released by China SFDA and officially launched to the market at the end of July 2009.

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. Sinovac's commercialized vaccines include Healive® (hepatitis A), Bilive® (combined hepatitis A and B), Anflu® (influenza) and Panflu(TM) (H5N1). Sinovac is currently developing Universal Pandemic Influenza vaccine and Japanese encephalitis vaccine. Additional information about Sinovac is available on its website, http://www.sinovac.com . To be added to our distribution list, please email: info@sinovac.com.

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 more information, please contact:

     Helen G. Yang

     Sinovac Biotech Ltd.

     Tel:   +86-10-8289-0088 x9871

     Fax:   +86-10-6296-6910

     Email: info@sinovac.com

   Investors:

     Amy Glynn/Sara Pellegrino

     The Ruth Group

     Tel:   +1-646-536-7023/7002

     Email: aglynn@theruthgroup.com

                spellegrino@theruthgroup.com

   Media

     Janine McCargo

     The Ruth Group

     Tel:   +1-656-536-7033

     Email: jmccargo@theruthgroup.com