<unk> , also known as the Sinovac COVID-19 vaccine, is an whole inactivated virus COVID-19 vaccine developed by the Chinese company Sinovac Biotech. It was Phase III clinical trialled in Brazil, Chile, Indonesia, the Philippines, and Turkey and relies on traditional technology similar to other inactivated-virus COVID-19 vaccines, such as the Sinopharm BIBP vaccine, another Chinese vaccine, and Covaxin, an Indian vaccine.<unk>  does not need to be frozen and both the final product and the raw material for formulating<unk>  can be transported refrigerated at 2–8 °C (36–46 °F), temperatures at which flu vaccines are kept. A real-world study of tens of millions of Chileans who received<unk>  found it 66% effective against symptomatic COVID-19, 88% against hospitalization, 90% against ICU admissions, and 86% against deaths. In Brazil, after 75% of the population in Serrana, São Paulo, received<unk> , preliminary results show deaths fell by 95%, hospitalizations by 86%, and symptomatic cases by 80%. In Indonesia, real world data from 128,290 healthcare workers showed 94% protection against symptomatic infection by the vaccine, beating results in clinical trials. Phase III results from Turkey published in The Lancet showed an efficacy of 84% based on 10,218 participants in the trials. Phase III results from Brazil previously showed 50.7% efficacy at preventing symptomatic infections and 83.7% effective in preventing mild cases needing treatment. Efficacy against symptomatic infections increased to 62.3% with an interval of 21 days or more between the doses.<unk>  is being used in vaccination campaigns in various countries in Asia, South America, Central America, and Eastern Europe. By April 2021, Sinovac had a production capacity of 2 billion doses a year. It is currently being manufactured at several facilities in China, with planned overseas manufacture in Brazil in September 2021 and eventually in Egypt and Hungary. On 1 June 2021, the World Health Organization (WHO) validated the vaccine for emergency use. Sinovac has signed purchase agreements for 380 million doses from COVAX. As of July 2021,<unk>  was the most widely used COVID-19 vaccine in the world, with 943 million doses delivered. As of 14 October 2021,<unk>  is the COVID-19 vaccine with most doses administered worldwide. A recent study jointly conducted by the LKS Faculty of Medicine, The University of Hong Kong (HKUMed) and the Faculty of Medicine, The Chinese University of Hong Kong (CU Medicine) showed that a third dose of Comirnaty vaccine given to those who received two doses of either Comirnaty or<unk>  provides protective levels of measured antibodies against the Omicron variant of SARS-CoV-2. Three doses of<unk>  however did not provide adequate levels of protective antibodies by the same measure, in direct contradiction to claims made by the vaccine manufacturer.
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