New COVID-19 vaccine, CoVac-1, offers better protection to immunocompromised patients, study reveals

A new COVID-19 vaccine has shown signs of inducing strong immune response especially in immonocompromised patients including those suffering from cancers like leukaemic and lymphoma. The findings of this response which was presented at the American Academy of Cancer Research (AACR) Annual Meeting in Louisiana, United States on Tuesday comes as early results from a small trial. The trial study on this vaccine shows that CoVac-1 induced T-cell immune responses in 93 per cent of patients with B-cell deficiencies.

Juliane Walz, senior author of the study, and a professor at the University Hospital Tubingen in Germany stated that CoVac-1 is currently the only peptide-based vaccine candidate specifically developed and evaluated for immunocompromised patients. In a peptide vaccine the protein pieces are injected directly, rather than being encoded via messenger RNA (mRNA).

According to the researchers, while vaccination provides a broad immune response against COVID-19 in most of the recipients, many approved vaccines have shown decreased efficacy in several immunocompromised people. The scientists also revealed that patients who were under treatments of blood cancers represent one such population, as their treatment regimens often damage healthy immune cells, particularly B cells, along with malignant ones.

At present, approved COVID-19 vaccines are dependent heavily on humoral responses, which may be impaired in patients with a B-cell deficiency. Enhancing the response from T cells which is another type of immune cells is one of the ways to overcome this issue.

Claudia Tandler, a graduate student at the University of Tubingen, who presented the study explained that the process requires the careful selection of SARS-CoV-2 antigens which are small pieces of viral proteins that can stimulate immune cells. While the current mRNA-based vaccines produce a larger piece of a single protein — the spike protein, the researchers chose six specific antigens from different parts of the virus, and not limited to spike, to build their vaccine.

In the phase I trial, the researchers selected 14 patients with a B-cell deficiency, including 12 patients with leukemia or lymphoma. Then, the patients were given a single dose of CoVac-1 and monitored for up to six months for safety and immune response. The scientists found that 64 per cent of the participants who had been previously vaccinated with an approved COVID-19 failed to elicit a humoral immune response.

The scientists also revealed that 14 days after vaccination, T-cell immune responses were observed in 71 per cent of patients, which rose to 93 per cent of patients 28 days after vaccination. When the scientists measured the potency of CoVac-1-induced T-cell responses they found increased spike-specific T-cell responses in B cell-deficient patients after vaccination with mRNA vaccines.

Currently, the researchers are preparing a phase III clinical trial to evaluate CoVac-1 in a larger population of immunocompromised individuals. The team is hopeful that the results will allow the vaccine to protect cancer patients with B-cell deficiencies from severe cases of COVID-19. The researchers also informed about the limitations of their study, including a relatively small sample size with low racial and ethnic diversity.

(With inputs from PTI)