Safety and immunogenicity of a hybrid-type vaccine booster in BBIBP-CorV recipients: a randomized controlled phase 2 trial

ABSTRACT

The emergence of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) variants with immune escape ability raises the urgent need for developing cross-neutralizing vaccines against the virus. NVSI-06-08 is a potential broad-spectrum recombinant COVID-19 vaccine that integrates the antigens from multiple SARS-CoV-2 strains into a single immunogen. Here, we evaluated the safety and immunogenicity of NVSI-06-08 as a heterologous booster dose in adults previously vaccinated with the inactivated vaccine BBIBP-CorV in a randomized, double-blind, controlled, phase 2 trial conducted in the United Arab Emirates (NCT05069129). Three groups of healthy adults over 18 years of age (600 participants per group) who had administered two doses of BBIBP-CorV 4-6-month, 7-9-month and >9-month earlier, respectively, were vaccinated with either a homologous booster of BBIBP-CorV or a heterologous booster of NVSI-06-08. The primary outcome was immunogenicity and safety of booster vaccinations. The exploratory outcome was cross-reactive immunogenicity against multiple SARS-CoV-2 variants of concerns (VOCs). The incidence of adverse reactions was low in both booster vaccinations, and the overall safety profile of heterologous boost was quite similar to that of homologous boost. Heterologous NVSI-06-08 booster was immunogenically superior to homologous booster of BBIBP-CorV. Both Neutralizing and IgG antibodies elicited by NVSI-06-08 booster were significantly higher than by the booster of BBIBP-CorV against not only SARS-CoV-2 prototype strain but also multiple VOCs. Especially, the neutralizing activity induced by NVSI-06-08 booster against the immune-evasive Beta variant was no less than that against the prototype strain, and a considerable level of neutralizing antibodies against Omicron (GMT 367.67; 95%CI, 295.50-457.47) was induced by heterologous booster, which was substantially higher than that boosted by BBIBP-CorV (GMT 45.03; 95%CI, 36.37-55.74). Our findings showed that NVSI-06-08 was safe and immunogenic as a booster dose following two doses of BBIBP-CorV, which was immunogenically superior to homologous boost with another dose of BBIBP-CorV. Our study also indicated that the design of hybrid antigen may provide an effective strategy for broad-spectrum vaccine developments.