Six Months Efficacy and Safety Results of Zifivax® Published in New England Journal of Medicine

On May 4, 2022, the team of Dr. George Fu Gao, Academician from Institute of Microbiology, Chinese Academy of Sciences (IMCAS) officially published phase III clinical trial results of the Recombinant COVID-19 Vaccine (CHO Cell) (trade name: Zifivax®) jointly developed by Anhui Zhifei Longcom Biopharmaceutical Co., Ltd. in the New England Journal of Medicine, one of the international leading medical academic journals. The study showed that, Zifivax® had good safety and efficacy six months after full vaccination, indicating good immune persistency of the vaccine.

The international multi-regional phase III clinical trial of the Recombinant COVID-19 Vaccine (CHO Cell) was performed at 31 clinical centers across Uzbekistan, Indonesia, Pakistan, and Ecuador; An additional center in China was included in the safety analysis only. A total of 28,904 participants aged 18 years old and above were recruited, of which 6.4% were over 60 years old, and randomized, double-blind and placebo-controlled methods were used to investigate the efficacy and confirm the safety of the vaccine.

The results showed that, the vaccine efficacy (VE) against COVID-19 of any severity among participants who completed full vaccination reached 81.4% (95% CI, 73.3-87.3), and the VE against severe-to-critical cases and death cases reached 92.9% (95% CI, 52.4-99.8) and 100%, respectively. The VE was 81.2% (95% CI,72.8-87.3) in people aged 18-59. In people aged 60 and above, the VE was 87.6% (95% CI,2.5-99.7). The VE against Delta and Alpha variants were 81.4% (95% CI,70.1-88.9) and 92.7% (95% CI,70.9-99.2), respectively.

In the long-term efficacy analysis of 6-month follow-up data after full vaccination (as of December 15^th, 2021), the VE against COVID-19 of any severity could still reach 75.7% (95% CI,71.0-79.8), and the VE against severe-to-critical cases and death cases reached 87.6% (95% CI,70.6-95.7) and 86.5% (95% CI,38.9-98.5), respectively. The VE against Delta and Alpha variants were 76.1% (95% CI,70.0-81.2) and 88.3% (95% CI,66.8-97.0), respectively.

In terms of safety profile of the vaccine, the phase III clinical trial results showed that the vaccine was safe among nearly 30,000 participants. The incidence of adverse events and serious adverse events in vaccine group and placebo group was similar, and there were no vaccine-related deaths reported. Most of the adverse reactions (98.5%) were mild (Grade 1 or 2). The incidence of adverse events in the elderly aged 60 and above was lower than the younger adult group, and all symptoms could be resolved with or without treatment.

The Recombinant COVID-19 Vaccine (CHO Cell) is jointly developed by IMCAS and Anhui Zhifei Longcom, the wholly-owned subsidiary of Chongqing Zhifei Biological Products Co., Ltd. On March 1, 2021, the vaccine was approved for marketing in Uzbekistan, which at the time was the first recombinant protein subunit COVID-19 vaccine registered for use in the world. On March 10, 2021, the vaccine was approved for emergency use in China. On February 19, 2022, it was approved as heterologous booster after prime immunization of two doses of inactivated vaccines in China. On March 1, 2022, the vaccine was approved for conditional marketing in China. At present, the Recombinant COVID-19 Vaccine (CHO Cell) has protected more than 100 million people all over the world, and has continued contributing to the prevention and control of the COVID-19 pandemic.

Paper link: https://www.nejm.org/doi/full/10.1056/NEJMoa2202261