The data from that preview have now been peer reviewed.
Although Sinovac is still at an earlier stage, Chinese researchers say their vaccine has the advantage that it can be stored at normal fridge temperatures of 2 to 8 degrees Celsius and may remain stable for up to three years.
Some context: The study comes after two Covid-19 vaccine candidates in the U.S. reported 95% efficacy.More news: Cuomo, de Blasio face blowback over handling of NYC school closures
Drugmakers of two rival vaccine candidates - one from Pfizer Inc. and Germany's BioNTech SE and another from Moderna Inc. - have each disclosed efficacy rates of more than 90%, higher than many had expected from vaccines developed so quickly. Data released in July showed the vaccine generated robust immune responses in adults aged 18 to 55.
The Oxford Vaccine Group's director, Andrew Pollard, said in a media briefing there were "lots of cases" of infections in its Phase III trial in Britain, Brazil and South Africa. It has also promised to deliver doses at no profit during the pandemic, and continuing afterward for poorer countries.
That was lower than antibodies from vaccine trials by world leaders Pfizer Inc. and Moderna Inc., which are using a different vaccine technology, and which recorded antibody levels in patients that were about the same as those who had contracted the virus.More news: Klay Thompson Suffers Lower Leg Injury, League Source Says It's 'Not Good'
'Older adults are a priority group for COVID-19 vaccination, because they are at increased risk of severe disease, but we know that they tend to have poorer vaccine responses'.
The study of 560 healthy adults - including 240 over the age of 70 - found the vaccine is better tolerated in older people compared with younger adults.
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What do the results show? "We and it's not a competition with the other developers", Oxford's Pollard said, adding that AstraZeneca would release headline efficacy data before it was published in an academic journal. This adenovirus doesn't infect humans but its presence trains our immune system to recognize these spike proteins as a danger. Those positive outcomes were present in all age groups given low and standard doses. So they included 200 people over 70 to be given the jab. Nor was there a wide range of backgrounds in the trial participants and "almost all participants of all ages were white and non-smokers".
"Our findings show that CoronaVac is capable of inducing a quick antibody response within four weeks of immunisation by giving two doses of the vaccine at a 14 day interval", said Fengcai Zhu, joint lead author of the study from the Jiangsu Provincial Centre for Disease Control and Prevention, Nanjing, China. The study also showed that adverse reactions to the vaccine were mild and the most common side effects were injection-site pain and tenderness, fatigue, headache, feverishness and muscle pain.