New Brazilian data show that the effective rate of Sinovac's SARS-CoV-2 vaccine is 50.4%

Publisher : BBC News Chinese / https://www.bbc.com/zhongwen/simp/science-55644206 / Translation, editing : Gan Yung Chyan, KUCINTA SETIA / Image courtesy (Sinovac's CoronaVac in Turkey) : Getty Images

The latest data released by Brazil shows that the overall effective rate of the CoronaVac vaccine developed by Sinovac Biotech is 50.4%. This figure barely meets the threshold required by global regulators, but is far lower than the 78% announced by Brazil last week. The data was submitted by the Butantan Institute in Sao Paulo to the Brazilian health regulator on Tuesday (12 January 2021). The Butantan Institute is a partner of Sinovac Biotech, and it is currently conducting the final phase of clinical trials of CoronaVac in Brazil. Researchers from the Institute explained that the decrease in effective rate was caused by including patients who were infected with SARS-CoV-2 but showed only "very mild" symptoms. "Very mild" symptoms

Last week, Brazilian researchers announced that the Sinovac vaccine trial had an effective rate of 78%, which they later called the "clinical effective rate." The researchers explained at a press conference on Tuesday (January 12) that they divided these cases into asymptomatic, very mild, mild, moderate, and severe. According to the report of the Institute, 78% of the previous "clinical effective rate" considered mild, moderate and severe cases, but if patients with "very mild" symptoms among volunteers are included, the new "overall effective rate" figure is 50.4%. These people do not need medical assistance. The researchers emphasized that this vaccine is still 78% effective in preventing mild cases requiring treatment, and 100% effective in moderate to severe cases. Currently, the World Health Organization and national regulatory agencies generally set the 50% effective rate as the threshold for vaccine qualification. "This vaccine reduces the intensity of the disease," said Ricardo Palacios, medical director of the Butantan Institute. He defended that the trial was conducted on medical staff who were highly exposed to the virus, and the interval between the two doses was very short, and that if it was extended to a wider community, the effect might be better. Image : The CoronaVac vaccine was jointly developed by Beijing Sinovac Biotechnology and Butantan Research Institute (EPA/Wu Hong)

The Butantan Institute also stated that the biggest side effects of the CoronaVac vaccine are local pain, headache and fatigue, but there is no record of any serious side effects. Brazil is one of the countries hardest hit by the covid pandemic. More than 8 million people have been infected with the new crown virus and the number of deaths ranks second in the world. The federal government is ready to start vaccinating the people with two vaccines. This vaccine is one of them. This has caused many people to pay great attention to the results of the test. Microbiologist Natalia Pasternak told reporters that the test results mean that the vaccine is not a panacea. "This is not the best vaccine in the world," she said, but she said it was a "fully acceptable vaccine." Different results

This vaccine named CoronaVac developed by Sinovac Biotechnology is an inactivated vaccine made from killed pathogens, which mainly induces the production of cellular immunity through antigens in it, Will not cause serious disease reactions. According to the New York Times, Sinovac has sold more than 300 million vaccines, mainly to low- and middle-income countries, accounting for about half of the total production capacity of vaccine manufacturers released by China in 2020. Many countries including Indonesia, Turkey and Singapore have ordered this vaccine, but its results in clinical trials in different countries are not the same. Last month, Turkish researchers stated that the effective rate of this vaccine was 91.25%, while Indonesia, which gave CoronaVac the green light on Monday, announced that its effective rate was 65.3%. Both of these are the interim results of Phase III clinical trials. In contrast, the United States Pfizer/BioNTech and Modena (Moderna) reported 95% and 94.1% respectively, and the Oxford/AstraZeneca vaccine has an effective rate of 70.4%. However, the two vaccines of Sinovac and Oxford/AstraZeneca have the same advantages-no need for ultra-low temperature storage, only a refrigerator refrigeration environment. But Modena's vaccine must be stored at minus 20 degrees Celsius, while the Pfizer/BioNTech vaccine must be stored at minus 70 degrees Celsius. This means that the first two can be used more effectively in developing countries, because those places may not have enough cryogenic storage facilities for vaccine storage. On Wednesday (January 13), Indonesian President Joko Widodo publicly vaccinated with CoronaVac on live TV. Sinovac Biotech has not yet announced the results of CoronaVac Phase III clinical trials in China, nor has it been approved for marketing. China's National Medical Products Administration approved the listing of a vaccine under the company's domestic competitor, Sinopharm Group, on 31 December 2020. However, China granted emergency use permission for CoronaVac very early. In November last year, several cities in Zhejiang have provided the people in need with the Sinovac vaccine. Brazil's dilemma

Despite being the most severely affected country in Latin America, Brazil's vaccination work has not progressed smoothly. BBC World Station Americas editor Candace Piette reported that Brazil has not yet announced a clear timetable for national vaccination. This delay is largely due to the government's disorder and fragmentation in vaccines. President Jair Bolsonaro has long rejected vaccines. Without providing evidence, he said that most Brazilians are unwilling to get vaccinated. He criticized CoronaVac more severely and banned the federal government from purchasing, but later withdrew the decision. Political analysts believe that this is mainly due to his political opponent, Sao Paulo Governor João Doria, who is a strong supporter of the vaccine. Brazil’s national immunization program currently relies on the vaccines of Sinovac and Oxford/AstraZeneca but they are both awaiting approval from Brazilian health regulators.