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SINOVAC's Varicella Vaccine Demonstrates Superior Safety in Head-to-Head Phase III Study Published in Vaccine
BEIJING, Oct. 25, 2025 – A head-to-head Phase III clinical trial published in Vaccines showed that SINOVAC's varicella vaccine had a more favorable safety profile than a WHO-prequalified comparator vaccine, while meeting non-inferiority criteria for immunogenicity in children aged 12 to 15 months.
The randomized, double-blind, active-controlled Phase III trial was conducted at San Juan de Dios Hospital in the Philippines and enrolled 484 healthy children aged 12 to 15 months. Participants were randomized to receive either SINOVAC's live attenuated varicella vaccine (n=239) or the comparator vaccine (n=245). The primary endpoint was the varicella-zoster virus antibody response rate (IgG ≥10 mIU/mL) six weeks post-vaccination, and secondary endpoints included geometric mean concentration (GMC) and safety.
According to the published analysis, the SINOVAC varicella vaccine met the predefined non-inferiority criteria for both seroresponse rate and GMC compared with the comparator vaccine. Safety analyses showed statistically significant differences in the incidence of adverse reactions between the two groups, with a lower overall rate of reported adverse reactions in the SINOVAC vaccine group. Differences were most notable for injection-site erythema. Two serious adverse events (0.82%) were reported in the comparator group during the study period.
SINOVAC's vaccine does not contain antibiotics, gelatin, and human serum albumin, removing several potential sources of hypersensitivity reactions.. In addition, its osmolarity is designed to be close to that of the human body, which may help reduce pain and local reactions during
Varicella is a highly contagious disease caused by the varicella-zoster virus and remains a public health concern in multiple countries. Vaccination is widely recognized as the most effective and economical preventive measure.
The head-to-head comparative data further strengthen the clinical evidence base for the SINOVAC's live attenuated varicella vaccine. The vaccine is currently the first and only varicella vaccine developed and manufactured in China to have received WHO prequalification, and it has been supplied to nearly 20 countries and regions, with cumulative distribution reaching tens of millions of doses.
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The full research paper, titled “Immunogenicity and Safety of a Live Attenuated Varicella Vaccine in Healthy Children Aged 12 to 15 Months: A Phase III, Randomized, Double-Blind, Active-Controlled Clinical Trial”, is available at: https://doi.org/10.3390/vaccines13090973
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.