South Africa Phase III Clinical Study Shows SINOVAC CoronaVac® Safe for Children as Young as 6 Months

Beijing, China, December 24, 2021 – SINOVAC Biotech Ltd. (NASDAQ: SVA) ("SINOVAC" or the "Company"), a leading provider of biopharmaceutical products in China, today announced results of a Phase III clinical study of its COVID-19 inactivated vaccine CoronaVac® in South Africa indicating safety for children from 6 months to 17 years. The results are part of an international, multi-center, case-driven, randomized, double blind, placebo-controlled Phase III clinical trial currently being held in South Africa, Chile, Malaysia, the Philippines and Kenya, investigating the immunogenicity, safety and efficacy of the SINOVAC COVID-19 vaccine in children and adolescents.

On October 28, subjects aged 6 to 35 months were recruited in South Africa and 200 volunteers were successfully enrolled in the Phase III clinical trial on December 20. No Grade-3 or above adverse events were reported. As of December 22, nearly 4,000 children in South Africa have participated in the trial with zero reported severe adverse events.

This follows several countries – including Chile, Ecuador, El Salvador, Colombia, Cambodia and Indonesia – approving the use of the SINOVAC COVID-19 vaccine for children of varying ages since September.

According to the latest data disclosed at a press conference held by the Joint Prevention and Control Mechanism of the State Council on December 20, more than 140 million children aged 3 to 11 years have received the COVID-19 vaccine in mainland China. Currently, only inactivated vaccines are approved for emergency use in this age group and a high level of antibody positive conversion was observed with the antibody level equal to, or higher than that of adults.

About SINOVAC's Phase I/II Trials in Children

On June 28, the Lancet Infectious Diseases online published the results of Phase I/II clinical studies of CoronaVac® in healthy children and adolescents aged 3 to 17 years in China with results showing good safety and tolerability, and a strong humoral immune response. On July 19, SINOVAC released the results of its world-first immunity persistence study of 180 individuals 3 to 17 years of age. It showed a 100% neutral antibody-positive conversion rate. The geometric mean titer (GMT) remained at a high level 28 days after the second dose, as well as another 3 months afterwards, which indicated that CoronaVac® induces stable and good immunogenicity.

About SINOVAC

SINOVAC Biotech Ltd., is a China-based biopharmaceutical company that focuses on the research, development, manufacturing and commercialization of vaccines that protect against human infectious diseases. SINOVAC's product portfolio includes vaccines against COVID-19, enterovirus71 (EV71), hepatitis A and B, seasonal influenza, 23-Valent pneumococcal polysaccharide ("PPV"), H5N1 pandemic influenza (avian flu), H1N1 influenza (swine flu), varicella and mumps. SINOVAC's COVID-19 vaccine, CoronaVac®, has been granted emergency use approval or conditional marketing authorization by over 40 countries or regions worldwide. Healive®, the hepatitis A vaccine manufactured by the Company, has passed the assessment under WHO prequalification procedures in 2017. The EV71 vaccine, an innovative vaccine developed by SINOVAC against hand foot and mouth disease caused by EV71, was commercialized in China in 2016. In 2009, SINOVAC was the first company worldwide to receive approval for its H1N1 influenza vaccine, which it has supplied to the Chinese Government's vaccination campaign and stockpiling program. The Company is also the only supplier of the H5N1 pandemic influenza vaccine to the government stockpiling program. The Company is developing several new products including a Sabin-strain inactivated polio vaccine and combined vaccines. SINOVAC primarily sells its vaccines in China, while also exploring growth opportunities in international markets. The Company is seeking market authorization of its products in over 30 countries outside of China. For more information, please see the Company's website at www.sinovac.com.