A new player has entered the COVID-19 vaccine game: CoVac-1, a multi-peptide vaccine designed to offer long-lasting immunity, has passed its first human trial. Proving itself to be safe and effective, the vaccine produced an immune response lasting at least three months and surpassing that of natural immunity or alternative vaccines.
The single-shot vaccine, based on SARS-CoV-2 proteins, induced immune cells, known as T cells, in 100 percent of participants 28 days after vaccination. Promisingly, the T cell response was not affected by any current variants of concern – Alpha, Beta, Delta, or Gamma. The results of the phase I clinical trial are published in Nature today.
T cell immunity is the primary goal of vaccine development, as T cells are the key to long-lasting protection.
When the body is infected with a pathogen, such as SARS-CoV-2, the immune system responds by sending white blood cells to attack it. First up are cells called macrophages, which engulf and digest the pathogen, leaving behind antigens. These are molecules that act as a marker of the invading pathogen and are recognized by antibodies. Antibodies are produced by the body’s second line of defense – B cells – and enable pathogens to be clumped together, where they can be destroyed by macrophages.
Finally, T cells attack infected cells and stimulate B cells to produce antibodies. After infection, a few T cells hang around, ready to spring into action if the body encounters the same pathogen again. These cells are aptly called “memory cells” and are what enable us to clear repeat infections so quickly.
Inducing a strong T cell response, therefore, is crucial for a vaccine's success. It is of particular importance for people with B cell deficiencies, such as patients with cancer, who rely more heavily on T cell immunity when fighting infections.
“CoVac-1 may well serve as a (complimentary) vaccine to induce T-cell immunity, particularly in elderly and immunocompromised individuals with impaired ability to mount sufficient immune responses after SARS-CoV-2 vaccination with currently approved vaccines,” the study authors write.
The team delivered the vaccine to 36 participants aged between 18 and 80 with no pre-existing T cell response to SARS-CoV-2. After an initial assessment on day one, the team continued to measure the T cell response of participants after seven, 14, 28, and 56 days, with a final assessment at the three-month mark.
They found no serious side effects and a whole load of T cells after almost a month. These persisted for at least three months – the duration of the trial.
The vaccine itself contains copies of various antigens derived from SARS-CoV-2 proteins, including the infamous spike protein, and the lesser talked about envelope, membrane, and nucleocapsid proteins.
How well CoVac-1 stacks up against these COVID-19 vaccine stalwarts remains to be seen.
For now, the vaccine is undergoing a phase II trial to test its efficacy in people with B cell and antibody deficiency. But, with any luck, a new COVID-19 vaccine offering long-lasting immunity could be on the horizon.