Vivo Capital Issues Letter to Sinovac Biotech Shareholders Addressing the Company’s False and Misleading Claims

Dear Fellow Sinovac Shareholders,

We, Vivo Capital (“Vivo”), write to you as fellow shareholders of Sinovac Biotech Ltd. (“Sinovac” or the “Company”) to address a number of statements in the April 29, 2025 letter from Sinovac’s Board of Directors (the “Board”) that we believe are false, and to reaffirm our commitment to upholding the best interests of all shareholders and to transparent corporate governance.

The Board has deceptively portrayed recent events as centering around a dispute with Vivo only. But the problem is at Sinovac’s Board, not at Vivo. In fact, Sinovac’s Board has precipitated a corporate governance crisis that threatens the Company’s future growth and has eroded its credibility with all shareholders. After the Privy Council ruled in January that five (5) directors had been elected in February 2018 consistent with Antiguan law, a new Board was installed—but contrary to the claims of the Board, its composition did not match the slate the Privy Council had considered. With no transparency, multiple directors have purportedly resigned and been replaced within three months, casting substantial uncertainty over the Company’s corporate governance and stability. Further, the Company’s independent auditor, Grant Thornton Zhitong Certified Public Accountants LLP, resigned in response to the Board’s April 1, 2025 statement that attempted to cast doubt on the validity of the Company’s corporate actions over the past seven years.¹ This resignation, in turn, prompted Sinovac’s own management to publicly express concerns that the current Board’s actions have disrupted Sinovac’s compliant operations and governance.²

Further, dissatisfaction with the current Board does not just come from Vivo. Another major shareholder, SAIF Partners, formally requisitioned a special meeting of shareholders, which will be held on July 8, to elect new directors to the Board.³

In its April 29 letter, the Board continued its attempts to rewrite the Company’s history. As shareholders, you will have an important decision regarding the future of your investment—so we want to ensure you have the accurate information regarding these matters: