149



                                  EXHIBIT 10.10
                                  -------------



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


                     Attached find the following materials:


   Cooperation Agreement on the Research and Development of Avian Flu Vaccine
   --------------------------------------------------------------------------
               for Human Use entered into between the Company and
               --------------------------------------------------
         the Center for Disease Control & Prevention of China, effective
         ---------------------------------------------------------------
                                December 15, 2004
                                -----------------











                                       150



                                  (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.





                                       151



                   Article III. Research & Division of Duties

1.     CDC will monitor and assess all future flu information and will embark on
       sustained  study of molecular  epidemiology on prevalent virus strains to
       promptly identify the strains that may lead to the flu epidemic.

2.     CDC will guide the planning of the research and  development of the avian
       flu  vaccine  for  human use and will  participate  in its  research  and
       development and the design of its production technology.

3.     Sinovac will use its  established  research and production  technology in
       vaccines  for human use to research and develop the avian flu vaccine for
       human use, and will be  responsible  for the reporting and  production of
       the vaccine.

4.     CDC will  undertake the genome  analysis of virus strains and the antigen
       analysis,  and will monitor the effects of immunity protection during the
       course of the  research  and  development  of the  vaccine.  It will also
       provide technical  guidance and requirements in the areas of vaccine use,
       vaccine storage and assessment of the effects of the vaccine.

                      Article IV: International Cooperation

Under the unified  organization and guidance of CDC, this Project will seek wide
international  cooperation  and will  engage  in  exchanges  with  international
bodies.  Sinovac will be responsible  for  international  cooperation  regarding
technological property rights and the signing of relevant documents.

                         Article V: Form of Cooperation

Sinovac and CDC will jointly form a key task team for the Project. If necessary,
a  corresponding  organization  will be set up to complete  the  research of the
avian flu vaccine for human use and other related projects.

Sinovac  and  CDC  will  each  have  one  person  specially   assigned  for  the
organization and  implementation  of the Project.  The two Parties will exchange
technicians according to the needs of the research.  Each side will also provide
proper research environment in their respective laboratories.






                                       152



                      Article VI: Funding for the Research

1.     Sinovac will be responsible  for funding the research and  development of
       the avian flu vaccine for human use,  including the introduction of virus
       strains;  patent application and the payment of fees; the examination and
       determination of vaccines and the costs of allocating research, etc.

2.     CDC will be responsible  for funding the study of avian flu  epidemiology
       among humans; molecular epidemiology and other related researches.

3.     The two Parties may jointly use this Project to apply for research  funds
       with the appropriate  Government  Departments,  to be used on the Project
       and other related purposes.

             Article VII: Ownership and sharing of technical results

1.     The two  Parties  agree that the  application  for new drug  certificate;
       production documents; patent and specialized technology for the avian flu
       vaccine for human use will be made in Sinovac's  name and will remain the
       properties of Sinovac.

2.     When the  products  of avian flu  vaccine  for  human use yield  economic
       benefits, Sinovac will provide funds gratis to CDC to support its work in
       the  investigation  of flu  epidemic  in China  and the  formulation  and
       implementation of prevention and cure planning.

3.     The two Parties will jointly  apply and  complete  all  applications  for
       awards with the state based on the results of the scientific  research of
       avian flu vaccine for human use. Any such award or honour will be jointly
       owned by both Parties.

4.     During the entire course of the two Parties  working  together to develop
       the avian flu  vaccine for human use,  the  publication  of any  relevant
       research results in domestic or foreign academic journals must first have
       the approval of both sides.  The  signature  for the results  shall be in
       accordance with the work performed and the amount of contribution by each
       Party.

                          Article VIII: Confidentiality

The two Parties  undertake  to maintain  strict  confidentiality  regarding  the
specialized  technology and related information for the research and manufacture
of the  vaccine.  Any  information  disclosed  to the  public,  including  news,
treatises, etc must be approved by both Parties.








                                       153



(no text proper on this page)

Sinovac Biotech Co. Ltd (seal) [content of seal unclear]
Representative: Yin Weidong [signature]
Date: 2004.11.29


Center for Disease Control & Prevention of China (seal)
[Seal of Center for Disease Control & Prevention of China]
Representative: [Signature. Characters illegible.]
Date: 2004.12.15

















- --------------------------------------------------------------------------------
Translator's Declaration:
I, Miguel Tu, Certified Translator and Member in good standing of the Society of
Translators and Interpreters of British Columbia, attest that, to the best of my
knowledge and belief, the document above is a true and accurate English
translation of a document in the Chinese language that appears to be a
[Cooperation Agreement between Sinovac and CDC].


Signed:   /s/ Miguel Tu                                  Date: December 28, 2004
          ------------------------
              Miguel Tu
Certified Translator. STIBC Membership No. 04-10-0685    Tel: 604-728-6181
Attorney General Accredited & STIBC Certified Court Interpreter
Member of Canadian Translators, Terminologists & Interpreters Council




                              End of Exhibit 10.10

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