A new COVID-19 vaccine might also protect cancer patients with weak immune systems, a new study found.

Researchers from the American Association for Cancer Research found that CoVac-1, a new vaccine developed in Germany, induced T-cell (part of the immune system that develop stem cells in the bone marrow to fight against infection and cancer) immune responses in 93 percent of patients with B-cell (a type of white blood cell that makes antibodies) deficiencies, including patients with lymphoma and leukemia.

“To our knowledge, CoVac-1 is currently the only peptide-based vaccine candidate specifically developed and evaluated for immunocompromised patients,” Juliane Walz, MD, senior author of the study and professor of peptide-based immunotherapy at the University Hospital Tübingen in Germany said in a statement on Tuesday.

Approved COVID-19 vaccines that are available at the moment induce an immune response in against the SARS-CoV-2, the virus that causes COVID-19, in some individuals but have, over time, proven to be less effective in patients with weaker immune systems. This has proven to be a major issue among cancer patients grappling with blood cancer and undergoing chemotherapy and other treatments that often destroy B-cells.

What differentiates CoVac-1 from traditional vaccines is that it directly targets specific pathogens within the body.

“In the clinic, we see many cancer patients who do not mount sufficient humoral immune responses after vaccination with available SARS-CoV-2 vaccines,” Walz said.

“These patients are thus at a high risk for a severe course of COVID-19.”

“T-cell immune responses against SARS-CoV-2 are of particular importance for patients with B-cell deficiencies, who develop very limited antibody responses after infection or vaccination,” said Claudia Tandler, MSc, a graduate student at the University of Tübingen, who presented the study.

“T cell-mediated immunity is indispensable for developing protective antiviral responses, and previous evidence has shown that T cells can combat COVID-19 even in the absence of neutralizing antibodies.”

Creating a vaccine that stimulates T-cells requires the careful selection of SARS-CoV-2 antigens—small pieces of viral proteins that can stimulate immune cells, Tandler added.

The researchers chose six specific antigens from different parts of the virus to design the vaccine. CoVac-1 is a peptide vaccine, meaning that the protein pieces are injected into it directly rather than encoded via mRNA.

“While the current mRNA-based vaccines produce a larger piece of a single protein—the spike protein—which our cells can break down into antigens, Tandler and colleagues chose six specific antigens from different parts of the virus (not limited to spike) to make up their vaccine. CoVac-1 is a peptide vaccine, meaning that the protein pieces are injected directly, rather than being encoded via mRNA,” the statement read.

The researchers previously tested the safety and preliminary efficacy of CoVac-1 in people without immune deficiencies. They found that all those who received the shot maintained robust T-cell responses three months after vaccination. These responses include the highly transmissible omicron variant and other variants of concern, with minimal side effects.

“CoVac-1 is designed to induce broad and long-lasting SARS-CoV-2 T-cell immunity, even in individuals who have impaired ability to mount sufficient immunity from a currently approved vaccine, and thus protect these high-risk patients from a severe course of COVID-19,” Walz said.

Limitations of this study include a relatively small sample size with low racial and ethnic diversity.