Leading Independent Proxy Advisory Firm ISS Joins Glass Lewis in Recommending Shareholders Vote to Keep the Current SINOVAC Board in Place ISS states, "[T]he [current] board appears to be working to pay SVA shareholders

Leading Independent Proxy Advisory Firm ISS

Joins Glass Lewis in Recommending Shareholders Vote to Keep the Current SINOVAC Board in Place

ISS states, "[T]he [current] board appears

to be working to pay SVA shareholders their fair share of dividends, and to resume trading of the company's shares, which are the two

most pressing issues currently facing SVA shareholders."

SINOVAC's Board of Directors encourages

shareholders to follow recommendations by ISS and Glass Lewis and VOTE the WHITE proxy card "AGAINST" the misguided proposals

to remove the SINOVAC Board and appoint the Reconstituted Imposter Former Board Slate

Special Meeting of SINOVAC shareholders to

be held on July 8, 2025

learn more, visit: VoteSinovac.com

BEIJING, July 4, 2025 - The Board of Directors of SINOVAC

Biotech Ltd. (NASDAQ: SVA) ("SINOVAC" or the "Company"), a leading provider of biopharmaceutical

products in China, today announced that leading independent proxy advisory firm Institutional Shareholder Services Inc. ("ISS")

has joined Glass, Lewis & Co. ("Glass Lewis") in recommending that SINOVAC shareholders vote to KEEP the current

SINOVAC Board in place by voting the WHITE proxy card "AGAINST" the election of the Reconstituted Imposter Former Board Slate

at the upcoming Special Meeting of Shareholders (the "Special Meeting").

The SINOVAC Board issued the following statement in response to ISS'

are thrilled that independent proxy advisors ISS and Glass Lewis recommended shareholders vote to KEEP SINOVAC's current Board

in place and OPPOSE the Reconstituted Imposter Former Board Slate. In making their recommendations, ISS and Glass Lewis both recognized

the swift actions the current SINOVAC Board has taken to restore fairness and deliver value to SINOVAC's rightful shareholders,

and they have criticized the Imposter Former Board's abject governance failures that robbed value from SINOVAC shareholders

during its seven-year "de facto" tenure.

"The facts speak for themselves: over the past four

months, the current SINOVAC Board has demonstrated its commitment to righting the wrongs of the Imposter Former Board. The current Board

has declared a US$55.00 per common share special cash dividend and has continued to lay the groundwork for additional distributions,

is working with NASDAQ to resume trading, and is launching a formal exploration of a future listing on the Stock Exchange of Hong Kong

to promote liquidity and support shareholder value creation.

"In contrast, the Imposter Former Board, in close

coordination with SAIF, Advantech/Prime Success ("Advantech/Prime") and Vivo Capital (together, "the Dissenting Investor

Group"), continue to attempt to derail our progress through misleading rhetoric, baseless claims and frivolous legal actions. Their

self-serving objective is clear: regain control of SINOVAC and deprive common shareholders of their rightful dividend payments.

"We urge shareholders to follow the recommendations

of both leading independent proxy advisory firms by voting AGAINST the election of the Reconstituted Imposter Former Board on

the WHITE proxy card."

Highlights from the ISS Report include1 (emphasis

SUPERIORITY OF THE CURRENT BOARD

POISON PILL AND NASDAQ TRADING HALT

IMPOSTER FORMER BOARD'S SELF-DEALING

At the Special Meeting, shareholders will have the chance to send

a clear message to the Dissenting Investor Group: SINOVAC will no longer be held captive to their self-dealing.

1 Permission to use quotations was neither sought nor obtained.

SINOVAC's Board urges shareholders to protect their investment

and the future of their Company by voting the WHITE proxy card today "AGAINST" Proposals 1 and 2 at the Special Meeting.

details on the misdeeds and shareholder harm caused by the Imposter Former Board and Dissenting Investor Group, visit our website www.votesinovac.com.

Your Vote is Important

Your vote on or before July 8 will be about the future of SINOVAC,

your receipt of your make-whole dividend payments in the near-term, and the long-term value of your investment.

We urge you to keep SINOVAC's Board in place and vote on the

WHITE proxy card "AGAINST" Proposal 1 to remove the current Board and "AGAINST" Proposal

2 to appoint the Reconstituted Imposter Former Board Slate. Your vote is critical to ensuring that SINOVAC remains on the path to stability,

growth, and value creation for all shareholders.

any items you received asking you to vote for the Reconstituted Imposter Former Board Slate. If you have already voted for the Reconstituted

Imposter Former Board Slate, you can subsequently revoke it by using the WHITE proxy card or WHITE voting instruction form to vote. Only

your latest-dated vote will count!

The Special Meeting of Shareholders will be held on Wednesday, July 9,

2025, at 8:00 a.m. China Standard Time (Tuesday, July 8, 2025, at 8:00 p.m. Atlantic Standard Time). Valid shareholders

of record as of the close of business on May 19, 2025, are entitled to vote at the meeting.

have any questions about locating your control number or voting your shares, please contact our proxy solicitor, Georgeson LLC, toll

free at (844) 568-1506 in the U.S and (646) 543-1968 outside the U.S. or via email at SinovacSpecialMeeting@georgeson.com.

Sinovac Biotech Ltd. (SINOVAC) is a China-based biopharmaceutical

company that focuses on the R&D, manufacturing, and commercialization of vaccines that protect against human infectious diseases.

SINOVAC's product portfolio includes vaccines against COVID-19, enterovirus

71 (EV71) infected Hand-Foot-Mouth disease (HFMD), hepatitis A, varicella, influenza, poliomyelitis, pneumococcal disease, etc.

The COVID-19 vaccine, CoronaVac , has been approved for use in

more than 60 countries and regions worldwide. The hepatitis A vaccine, Healive , passed WHO prequalification requirements in

2017. The EV71 vaccine, Inlive , is an innovative vaccine under "Category 1 Preventative Biological Products"

and commercialized in China in 2016. In 2022, SINOVAC's Sabin-strain inactivated polio vaccine (sIPV) and varicella

vaccine were prequalified by the WHO.

SINOVAC was the first company to be granted approval for its H1N1

influenza vaccine Panflu.1 , which has supplied the Chinese government's vaccination campaign and stockpiling program. The

Company is also the only supplier of the H5N1 pandemic influenza vaccine, Panflu , to the Chinese government stockpiling program.

SINOVAC continually dedicates itself to new vaccine R&D, with

more combination vaccine products in its pipeline, and constantly explores global market opportunities. SINOVAC plans to conduct

more extensive and in-depth trade and cooperation with additional countries, and business and industry organizations.

Important Additional Information and Where to Find It

with SINOVAC's Special Meeting, SINOVAC has filed with the U.S. Securities and Exchange Commission ("SEC")

and mailed to shareholders of record entitled to vote at the Special Meeting a definitive proxy statement and other documents, including

a WHITE proxy card. SHAREHOLDERS ARE ENCOURAGED TO READ THE PROXY STATEMENT AND ALL OTHER RELEVANT DOCUMENTS WHEN FILED WITH THE

SEC AND WHEN THEY BECOME AVAILABLE BECAUSE THOSE DOCUMENTS WILL CONTAIN IMPORTANT INFORMATION. Investors and other interested parties

will be able to obtain the documents free of charge at the SEC's website, www.sec.gov, or from SINOVAC at its

website: https://www.sinovac.com/en-us/Investors/sec filings. You may also obtain copies of SINOVAC's definitive proxy

statement and other documents, free of charge, by contacting SINOVAC's Investor Relations Department at ir@sinovac.com.

Safe Harbor Statement

This announcement contains forward-looking statements within the meaning

of Section 21E of the Securities Exchange Act of 1934, as amended, and as defined in the U.S. Private Securities Litigation Reform

Act of 1995. These forward-looking statements can be identified by terminology such as "may," "will," "expect,"

"anticipate," "aim," "estimate," "intend," "plan," "believe,"

"potential," "continue," "is/are likely to" or other similar expressions. Such statements are based

upon current expectations and current market and operating conditions and relate to events that involve known or unknown risks, uncertainties

and other factors, all of which are difficult to predict and many of which are beyond the Company's or Board's control, which

may cause actual results, performance or achievements to differ materially from those in the forward-looking statements. Further information

regarding these and other risks, uncertainties or factors is included in the Company's filings with the U.S. Securities and Exchange

Commission. The Company and Board do not undertake any obligation to update any forward-looking statement as a result of new information,

future events or otherwise, except as required under law.

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