The physical conditions of the vaccine receivers are being closely monitored through immunopathological analysis, cytokine detection and neutralizing antibody monitoring, a key indicator for the vaccine's efficacy, said Zhang Yuntao, vice president of the China National Biotec Group (CNBG), a subsidiary of the China National Pharmaceutical Group (Sinopharm), which developed one of the vaccines.
The clinical trial, which began on April 12, will include 288 volunteers in the first phase and 1,108 in the second phase, all of them healthy and aged over six.
They are divided into four groups: those receiving low doses, medium doses, high doses and a placebo.
The inactivated vaccine uses the dead virus to implant an immune cell memory, so when the real coronavirus attacks, it induces the immune response. The vaccine has the advantages of mature production processes, controllable quality standards and wide-ranging protection range.
Its development took several painstaking processes, Yang Xiaoming, president of CNBG told the Science and Technology Daily.
After isolating virus strains of the novel coronavirus, researchers had to test whether the strains were suitable for production of a vaccine, as they may differ in toxicity and reproductive capacity.
Researchers screened them and selected those suitable as vaccine seeds in a three-tier virus seed bank. Then they made a culture in the vero cells to keep the selected strains alive and stable.
"These processes must be conducted in biological laboratories with high security," Yang said.
At the same time, researchers explored inactivation and purification processes, formula adjuvant and vaccine doses, which are key to the vaccine's safety and efficacy, Yang added.
The research team used two kinds of monkeys, three kinds of mice, rabbits and guinea pigs to carry out virus attack tests before clinical trials.
Drawing on previous experience in SARS vaccine development, Sinovac, the other inactivated vaccine developer, cooperated closely with institutions including the Chinese Center for Disease Control and Prevention and the Institute of Laboratory Animal Sciences under the Chinese Academy of Medical Sciences.
Since the vaccine project was launched on Jan. 28, the company had sent researchers to P3 laboratories, where the virus can be contained, in Zhejiang Province and Beijing to conduct strain screening and develop vaccine preparation methods. Researchers worked against the clock to finish preclinical studies of the vaccine, Sinovac CEO Yin Weidong said at a press conference.
Wang Junzhi, an academician with the Chinese Academy of Engineering, said vaccines entering clinical trials marked important progress. However, they were still a long way from the market as the third phase of the clinical trial could involve thousands of people to finally determine its effectiveness.
Even in an emergency, the evaluation criteria for vaccine safety and effectiveness cannot be lowered during the trial process, Wang said.
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