The efficacy, safety and immunogenicity Nanocovax: results of a randomized, double-blind, placebo-controlled Phase 3 trial
Authors: Nguyen Thuy P. , Do Quyet , Phan Lan T. , Anh Dang D. , Khong Hiep , Nguyen Thuong V. , Hoang Luong V. , Dinh Duc V. , Pham Hung N. , Chu Men V. , Nguyen Toan T. , Pham Quang D. , Le Tri M. , Trang Tuyen N.T. , Dinh Thanh T. , Vo Thuong V. , Vu Thao T. , Nguyen Quynh B.P. , Phan Vuong T. , Nguyen Luong V. , Nguyen Giang T. , Tran Phong M. , Nghiem Thuan D. , Tran Tien V. , Nguyen Tien G. , Tran Tuynh Q. , Nguyen Linh T. , Do Anh T. , Nguyen Dung D. , Ho Son A. , Nguyen Viet T. , Pham Dung T. , Tran Hieu B. , Vu Son T. , Hoang Su X. , Do Trung M. , Nguyen Xuan T. , Le Giang Q. , Tran Ton , Cao Thang M. , Dao Huy M. , Nguyen Thao T.T. , Doan Uyen Y , Le Vy T.T. , Tran Linh P. , Nguyen Ngoc M. , Nguyen Ngoc T. , Pham Hang T.T. , Nguyen Quan H. , Nguyen Hieu T. , Nguyen Hang L.K. , Trang Nguyen V. , Nguyen Anh T.L. , Nguyen Linh T. , Nguyen Anh P. , Trinh Nhung T.H. , Le Ly T.K. , Tran Van T. B. , Chu Mai T. N. , Phan My H. , Phan My H. , Nguyen Hoa T. H. , Tran Vinh T. , Tran Mai T.N. , Nguyen Truc T.T. , Ha Phat T. , Huynh Hieu T. , Nguyen Khanh D. , Duong Nghia H.T. , Thuan Ung T. , Doan Chung C. , May  , Do Si M. 
Published: March 2022

Background

Nanocovax is a recombinant severe acute respiratory syndrome coronavirus 2 subunit vaccine composed of full-length prefusion stabilized recombinant SARS-CoV-2 spike glycoproteins (S-2P) and aluminum hydroxide adjuvant. In a Phase 1 and 2 studies, (NCT04683484) the vaccine was found to be safe and induce a robust immune response in healthy adult participants.

Methods

We conducted a multicenter, randomized, double-blind, placebo-controlled study to evaluate the safety, immunogenicity, and protective efficacy of the Nanocovax vaccine against Covid-19 in approximately 13,007 volunteers aged 18 years and over. The immunogenicity was assessed based on Anti-S IgG antibody response, surrogate virus neutralization, wild-type SARS-CoV-2 neutralization and the types of helper T-cell response by intracellular staining (ICS) for interferon gamma (IFNg) and interleukin-4 (IL-4). The vaccine efficacy (VE) was calculated basing on serologically confirmed cases of Covid-19.

Findings

Up to day 180, incidences of solicited and unsolicited adverse events (AE) were similar between vaccine and placebo groups. 100 serious adverse events (SAE) were observed in both vaccine and placebo groups (out of total 13007 participants). 96 out of these 100 SAEs were determined to be unrelated to the investigational products. 4 SAEs were possibly related, as determined by the Data and Safety Monitoring Board (DSMB) and investigators. Reactogenicity was absent or mild in the majority of participants and of short duration. These findings highlight the excellent safety profile of Nanocovax.

Regarding immunogenicity, Nanocovax induced robust IgG and neutralizing antibody responses. Importantly, Anti S-IgG levels and neutralizing antibody titers on day 42 were higher than those of natural infected cases. Nanocovax was found to induce Th2 polarization rather than Th1.

Post-hoc analysis showed that the VE against symptomatic disease was 51.5% (95% confidence interval [CI] was [34.4%-64.1%]. VE against severe illness and death were 93.3% [62.2-98.1]. Notably, the dominant strain during the period of this study was Delta variant.

Interpretation

Nanocovax 25 microgram (mcg) was found to be safe with the efficacy against symptomatic infection of Delta variant of 51.5%.

Funding

Research was funded by Nanogen Pharmaceutical Biotechnology JSC., and the Ministry of Science and Technology of Vietnam; ClinicalTrials.gov number, NCT04922788.