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BEIJING: A candidate coronavirus vaccine developed by the Chinese Academy of Sciences (CAS) was found to be safe and elicits immune responses in early and mid-stage trials, researchers said on Tuesday (December 22).
A late-stage trial of the ZF2001 vaccine, which CAS is developing with a Chongqing Zhifei biologicals unit, began last month in China. Its goal is to recruit 29,000 people in China, Uzbekistan, Indonesia, Pakistan and Ecuador.
The candidate did not cause serious adverse events, with common mild side effects including injection pain, redness and swelling, researchers from the Chongqing Zhifei unit, CAS and other Chinese institutes said in a paper published Tuesday ahead of peer review.
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The combined data from the Phase 1 and 2 trials involved 950 healthy Chinese participants aged 18 to 59 years. Low and high dose versions were tested, and the Phase 2 study also evaluated two doses versus three doses for the low and high dose versions.
The highest dose administered by three injections spaced 30 days apart did not induce an enhanced immune response compared to the lowest dose, according to the paper. The Phase 3 trial will look at the lowest-dose version given in three injections, he said.
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Neutralizing antibodies against the virus were detected among at least 93 percent of the participants who received three injections in different groups. Levels of antibodies activated by the vaccine were higher than those seen in samples from patients recovered from the disease, the researchers said.
However, these antibody-based readings are not enough on their own to predict how effective ZF2001 will be in protecting people from the virus, the researchers said, cautioning that they could not yet determine the duration of immune responses.
The vaccine also triggered moderate cell-based immune responses, a crucial part of the human immune system that works differently from antibodies.
ZF2001 is a protein subunit vaccine, which uses a harmless part of the SARS-CoV-2 virus instead of the entire germ.
Four other Chinese vaccines from Sinopharm, Sinovac Biotech and CanSino Biologics have also entered phase 3 clinical trials.
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