[SCHEDULE 13G (Amendment No. SINOVAC BIOTECH LTD. (Name of Issuer) (Title of Class of Securities) (CUSIP Number) (Date of Event Which Requires Filing of This Statement) o Rule 13d-1(b) x Rule 13d-1(c) o Rule 13d-1(d) *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]