ABSTRACT
Background: T cell immunity is key for the control of viral infections including SARS-CoV-2, in particular with regard to immune memory and protection against arising genetic variants. Method: We recently evaluated a peptide-based SARS-CoV-2 T cell activator termed CoVac-1 in a first-in-human clinical trial and observed a favorable safety profile and induction of poly-specific T cell responses until month 3. Here, we report on long-term safety and efficacy data of CoVac-1 in healthy adults until month 12. Findings: CoVac-1 is well tolerated without long-term immune-related side effects and induces long-lasting anti-viral T cell responses in 100% of study participants. Potent expandability of CD4+ and CD8+ T cells targeting multiple different CoVac-1 T cell epitopes was observed 6 and 12 months after one single dose of CoVac-1. T cell responses were associated with the severity and the number of local adverse events at injection site. Beyond induction of T cell immunity, 89% of study participants developed CoVac-1-specific IgG antibody titers which associated with the intensity of the T cell response, indicating that CoVac-1-specific CD4+ T cells support the induction of B cell responses. Vaccination with approved COVID-19 vaccines boosted CoVac-1-specific T cell responses. Overall, a low SARS-CoV-2 infection rate was observed in the study population (8.3% of participants until month 12). Interpretation: Together, a single application of CoVac-1 elicits long-lived and broad SARS-CoV-2-specific T cell immunity, which further supports the current evaluation of our T cell activator in patients with congenital or acquired B cell defects (NCT04954469). Funding: This trial is funded by the Ministry of Science, Research and the Arts Baden-Wuerttemberg., Germany