Clinical trials in Brazil of a Chinese-made vaccine against Covid-19 have shown “extremely positive” results, and a widespread vaccination campaign could begin as early as December, the governor of Sao Paulo state said on Wednesday. Sao Paulo, the epicentre of the coronavirus pandemic in hard-hit Brazil, is one of six states helping to test the so-called CoronaVac vaccine developed by Chinese pharmaceutical firm Sinovac Biotech. The vaccine produced an immune response in 98 per cent of recipients over 60 years old, with no adverse side-effects reported so far, said Governor Joao Doria. “The results have been extremely positive,” he told a news conference. “We will soon be able to immunise Brazilians in Sao Paulo and across the country with the CoronaVac vaccine … The projected delivery date is in December this year.” Sinovac has partnered with a Brazilian public health research centre, the Butantan Institute, to conduct Phase 3 clinical trials of the vaccine – the last step before regulatory approval. The deal gives the institute the right to produce 120 million doses of the vaccine, according to officials. CoronaVac has become caught up in a political battle in Brazil, however. President Jair Bolsonaro, whose administration has tense relations with China, has criticised the vaccine, and lashed out at Doria, a leading opponent, for supposedly backing it. The far-right president has instead allocated 1.9 billion reals (US$360 million) to purchase another vaccine candidate, developed by Oxford University and pharmaceutical firm AstraZeneca. Brazil Covid-19 deaths pass 100,000 as country struggles to contain pandemic Trials of that vaccine, which is also being tested partly in Brazil, were suspended on Tuesday after a volunteer recipient developed an unexplained illness – a move the company described as “routine”. Brazil has the second-highest death toll in the pandemic after the United States, with more than 127,000 people killed and 4.1 million infections. The South American country has emerged as a leading testing ground for vaccines. In the latest development, Brazilian medical diagnostics company Dasa and US vaccine maker Covaxx announced a deal on Wednesday to conduct Phase 2 and 3 trials of the latter’s Covid-19 vaccine in Brazil. Covaxx, a subsidiary of US firm United Biomedical, plans to test the vaccine on at least 3,000 volunteers in Brazil.