Abstract
The development of effective and safe COVID-19 vaccines is a major move forward in our global effort to control the SARS-CoV-2 pandemic. The aims of this study were (1) to develop an inactivated whole-virus SARS-CoV-2 candidate vaccine named BIV1-CovIran and (2) to determine the safety and potency of BIV1-CovIran inactivated vaccine candidate against SARS-CoV-2. Infectious virus was isolated from nasopharyngeal swab specimen and propagated in Vero cells with clear cytopathic effects in a biosafety level-3 facility using the World Health Organization's laboratory biosafety guidance related to COVID-19. After characterisation of viral seed stocks, the virus working seed was scaled-up in Vero cells. After chemical inactivation and purification, it was formulated with alum adjuvant. Finally, different animal species were used to determine the toxicity and immunogenicity of the vaccine candidate. The study showed the safety profile in studied animals including guinea pig, rabbit, mice and monkeys. Immunisation at two different doses (3 or 5 μg per dose) elicited a high level of SARS-CoV-2 specific and neutralising antibodies in mice, rabbits and nonhuman primates. Rhesus macaques were immunised with the two-dose schedule of 5 or 3 μg of the BIV1-CovIran vaccine and showed highly efficient protection against 104 TCID50 of SARS-CoV-2 intratracheal challenge compared with the control group. These results highlight the BIV1-CovIran vaccine as a potential candidate to induce a strong and potent immune response that may be a promising and feasible vaccine to protect against SARS-CoV-2 infection.