SINOVAC Initiates Phase Ⅲa Clinical Trial of Quadrivalent Vaccine Against Hand, Foot, and Mouth Disease (HFMD)

Beijing, China - Sinovac Biotech Ltd. ("SINOVAC" or the "Company") (NASDAQ: SVA), a leading provider of biopharmaceutical products in China, initiated enrollment for a Phase IIIa clinical trial of its self-developed quadrivalent inactivated enterovirus vaccine (HFMD4, Vero cell) candidate to prevent HFMD caused by Enterovirus 71 (EV71), Coxsackievirus A16 (CA16), Coxsackievirus A10 (CA10), and Coxsackievirus A6 (CA6).

The initiation and investigator meeting for the Phase Ⅲa clinical trial of the quadrivalent enterovirus inactivated vaccine (Vero cell) were held in Henan Province, China.

The Phase Ⅲa clinical trial is designed to be a multicenter, randomized, double-blind, placebo-controlled trial to evaluate the efficacy, safety, and immunogenicity of this vaccine candidate in infants and young children aged 6 to 71 months.

Previous Phase Ⅰ and Ⅱ trials demonstrated that the vaccine was well-tolerated and safe in children in this age group. Data also showed that two doses of HFMD4 can elicit robust neutralizing antibody responses against all four virus serotypes within 30 days after the second vaccination.

By developing multivalent vaccines such as HFMD2 and HFMD4, SINOVAC aims to protect against a broader range of enteroviruses and address the limitations of cross-protection among different serotypes. SINOVAC’s HFMD2 (EV71 and CA16), as the world’s first bivalent HFMD vaccine candidate under Phase Ⅲ clinical trial evaluation, successfully obtained primary endpoint data and safety monitoring data from the first epidemic season in March 2026. Preliminary results indicate that the vaccine candidate exhibits a favorable safety profile and satisfactory efficacy results.

As the development of both bivalent and quadrivalent HFMD vaccines advances steadily, SINOVAC’s pipeline for multivalent enterovirus vaccines continues to expand. These candidates are expected to strengthen scientific support and offer additional options for HFMD prevention worldwide. The company remains committed to advancing clinical trials to provide more comprehensive immunization strategies against HFMD.

About SINOVAC

Sinovac Biotech Ltd. (SINOVAC) is a China-based global biopharmaceutical company, with a mission of "supply vaccines to eliminate human diseases", the company specializes in the research, development, manufacturing and commercialization of vaccines and related biological products that protect against human infectious diseases.

The company's diversified portfolio includes vaccines for influenza, viral hepatitis, varicella, Hand-Foot-Mouth disease (HFMD), poliomyelitis, pneumococcal disease, etc., of which 3 vaccines have been prequalified by WHO, including inactivated hepatitis A vaccine Healive®, Sabin-strain inactivated polio vaccine (sIPV), and varicella vaccine.

SINOVAC has a leading edge in developing vaccines to combat infectious disease outbreaks and was among the first to initiate R&D during major public health emergencies, including SARS, H5N1, H1N1, and COVID-19. The company developed the world's first inactivated SARS vaccine (Phase I completed), China's first H5N1 influenza vaccine (Panflu®), the world's first H1N1 influenza vaccine (Panflu.1®), and CoronaVac®, the most widely used inactivated COVID-19 vaccine globally.

Beyond its marketed portfolio, the company is advancing a robust pipeline that includes combination vaccines, recombinant protein vaccines and next-generation platforms such as mRNA technologies and antibodies.

With a long-standing commitment to innovation and global health, SINOVAC is expanding its global footprint by strengthening partnerships with research institutions, international organizations, and local partners. Through broader market presence, technological cooperation, and localized production, the company aims to accelerate vaccine development and supply, enhance regional access to high-quality products, and better address unmet medical needs while improving preparedness for future pandemics.

For more information, please see the Company's website at www.sinovac.com.cn or www.sinovac.com.