Phase III Clinical Trial of Recombinant COVID-19 Vaccine (Sf9 Cells)

The emergence of COVID-19 in December 2019 was declared a Public Health Emergency of International Concern (PHEIC) by the World Health Organization (WHO) on 30 January 2020. The COVID-19 pandemic has placed heavy economic pressure, medical burden, and severe harm to people's lives and well-being.

In response to this unpredictable outbreak, the State Key Laboratory of Biotherapy at West China Hospital of Sichuan University, along with the scientific team at WestVac Biopharma Co., Ltd (WestVac), developed a Recombinant COVID-19 vaccine (Sf9 cells). This vaccine, composed of adjuvant and recombinant severe acute respiratory syndrome-coronavirus 2 (SARS-CoV-2) spike protein receptor binding domain (S-RBD) protein expressed in insect cells, aims to prevent COVID-19.

Phase I Results

The initial results from phase I trials showed that this vaccine is both safe and immunogenic. Preliminary safety analysis indicated an adverse reaction rate below 30%, with all reactions being mild and limited to injection sites or systemic responses. No serious adverse reactions were recorded.

Regarding immunogenicity, the seroconversion rate of live virus-neutralizing antibodies reached 100%. The geometric mean titer (GMT) of live virus-neutralizing antibodies, as measured by cytopathic methods, was comparable to those of mRNA vaccines developed by Pfizer and Moderna. Phase II clinical trials, involving over 900 participants, demonstrated similarly favorable safety outcomes.

Phase III Trial Implementation

Based on the promising results from phases I and II, phase III clinical trials were conducted across the Philippines, Indonesia, Kenya, and Nepal. In Nepal, SOLID Nepal implemented the phase III clinical trial of the recombinant COVID-19 vaccine (Sf9 cells) in Chitwan.

The primary objective of the study was to evaluate the efficacy, safety, and immunogenicity of the recombinant COVID-19 vaccine (Sf9 cells) for preventing COVID-19 in adults aged 18 years and older. A total of 1271 participants received three doses of the (Sf9 cells) vaccine, completing all follow-up visits as per the protocol.

This trial marks a significant advancement in the global fight against COVID-19, contributing hope for a safer and healthier future for communities worldwide.