GRAd-COV2, a gorilla adenovirus-based candidate vaccine against COVID-19, is safe and immunogenic in younger and older adults

Description GRAd-COV2, a candidate vaccine for COVID-19 based on a gorilla adenovirus, is safe and immunogenic in younger and older adults. A gorilla adenovirus vaccine for COVID-19 Multiple COVID-19 vaccines currently in-use use adenoviral vectors for delivery of the SARS-CoV-2 spike protein. However, as these vaccines use human or closely related chimpanzee adenoviruses, there is increased likelihood of preexisting antivector immunity, which may dampen the response to the vaccine. To avoid this, Lanini et al. developed GRAd-COV2, a gorilla adenovirus-based SARS-CoV-2 vaccine. Here, the authors report the results of a phase 1, dose-escalation, open-labeled clinical trial showing that GRAd-COV2 was safe and immunogenic in both younger (aged 18 to 55 years old) and older (aged 65 to 85 years old) adults. In addition, participants had little to no preexisting immunity to the gorilla adenoviral vector. Together, these results support the further development of GRAd-COV2 as a COVID-19 vaccine. Safe and effective vaccines against coronavirus disease 2019 (COVID-19) are essential for ending the ongoing pandemic. Although impressive progress has been made with several COVID-19 vaccines already approved, it is clear that those developed so far cannot meet the global vaccine demand alone. We describe a COVID-19 vaccine based on a replication-defective gorilla adenovirus expressing the stabilized prefusion severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) spike protein named GRAd-COV2. We assessed the safety and immunogenicity of a single-dose regimen of this vaccine in healthy younger and older adults to select the appropriate dose for each age group. For this purpose, a phase 1, dose-escalation, open-labeled trial was conducted including 90 healthy participants (45 aged 18 to 55 years old and 45 aged 65 to 85 years old) who received a single intramuscular administration of GRAd-COV2 at three escalating doses. Local and systemic adverse reactions were mostly mild or moderate and of short duration, and no serious adverse events were reported. Four weeks after vaccination, seroconversion to spike protein and receptor binding domain was achieved in 43 of 44 young volunteers and in 45 of 45 older participants. Consistently, neutralizing antibodies were detected in 42 of 44 younger-age and 45 of 45 older-age volunteers. In addition, GRAd-COV2 induced a robust and T helper 1 cell (TH1)–skewed T cell response against the spike protein in 89 of 90 participants from both age groups. Overall, the safety and immunogenicity data from the phase 1 trial support the further development of this vaccine.