EXHIBIT 10.10 Cooperation Agreement on the research and development of avian flu vaccine for human use between Sinovac Biotech Co. Ltd and the Center for Disease Control & Prevention of China

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                                  EXHIBIT 10.10

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           This is an Exhibit to the Form 20-F of Sinovac Biotech Ltd.

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                     Attached find the following materials:

   Cooperation Agreement on the Research and Development of Avian Flu Vaccine

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               for Human Use entered into between the Company and

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         the Center for Disease Control & Prevention of China, effective

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                                December 15, 2004

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                                  (Translation)

              Cooperation Agreement on the research and development

                   of avian flu vaccine for human use between

                         Sinovac Biotech Co. Ltd and the

                Center for Disease Control & Prevention of China

              Article I: Purpose of cooperation and name of Project

The research and  development of avian flu vaccine for human use is an important

component of China's flu prevention and cure system.  Incorporating the research

and  development  of the vaccine  into the total  framework  of China's  disease

control and prevention will help increase the efficiency of its performance.  In

order to complement  each other with their own  resources,  and to  successfully

produce an avian flu vaccine for human use in the shortest possible time to meet

the state's needs in the prevention and cure of the flu, Sinovac Biotech Co. Ltd

(Sinovac)  and the Center for Disease  Control and  Prevention  of China  (CDC),

through friendly consultations,  have agreed to cooperate with each other in the

research and development of the avian flu vaccine for human use.

                       Article II: The Cooperating Parties

Sinovac  Biotech  Co.  Ltd  is a  Company  that  specializes  in  the  research,

development,  production  and sale of vaccines  for human use. Its mission is to

provide  vaccines for human beings to eliminate  diseases.  Since its inception,

the Company has successfully developed the hepatitis A vaccine inactivated;  the

combined  vaccine for hepatitis A and B; the flu splitting  vaccine and the SARS

vaccine inactivated, etc. It has rich experience in the research and development

of vaccines as well as a team of professional technicians.

The Center for Disease  Control and  Prevention of China is a Government  public

service agency  responsible for the  implementation  of national disease control

and  prevention,  as  well as the  management  of  public  health  services  and

technology.  Its  mission is to create a healthy  environment,  maintain  social

stability,  safeguard the security of the state and to promote the health of the

people  through  the  prevention  and  control  of  diseases,   deformities  and

impairments.  Its aim is to rely on scientific  research based on the ability of

its personnel, concentrating on disease control.

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