CoVac-1, a promising candidate vaccine

One of the solutions against the SARS-CoV-2 virus, which is responsible for COVID-19, is vaccines that are able to confer long-lasting immunity, especially in sectors of the population at high risk from complications. Currently available vaccines bring about a strong neutralising antibody response. But T lymphocytes also play an important role in antiviral defences by destroying infected cells.

The CoVac-1 vaccine is, however, different to other vaccines. It was designed to induce a strong T cell response targeting SARS-CoV-2. Researchers at the University of Tübingen (Germany) have carried out phase 1 clinical trials in order to evaluate the safety and effectiveness of this candidate vaccine.

36 participants aged between 18 and 80 years were recruited and given a single dose of the CoVac-1 vaccine. The vaccine is made up of many T cell epitopes derived from different SARS-CoV-2 proteins. The scientists firstly tested its safety by noting any side-effects up to 56 days after vaccination. The majority of side effects  were slight to moderate. The most severe involved erythema (redness) at the injection site, affecting nearly 20% of patients, and resolving in an average of 2 days. 

The researchers then analysed the immunogenicity of this vaccine, that is, the immune reaction that it triggers. In all participants, local stimulation of T cells was observed, without any generalised inflammatory reaction, with a continued T cell response during the whole length of the study, that is, up to 3 months. This production of anti-SARS-CoV-2 T cells was similar to that observed during natural infection, but with a much greater intensity.

This vaccine is potentially very useful, notably for patients with a limited humoral (i.e. antibody) immunity who are at high risk of serious forms of COVID-19, such as certain cancer patients. Studies involving a greater time period and more participants are currently underway.