“It is very important for cancer patients and their practitioners worldwide to know that they can be vaccinated against corona during their treatment and that this vaccination is safe,” says Liesbeth de Vries, professor of Medical Oncology at the UMCG and research leader of the VOICE- study (Vaccination against covid In Cancer).
A total of 503 patients with solid tumors and 240 control subjects, all partners of the patients, were vaccinated with the Moderna mRNA vaccine. They received two doses four weeks apart. The first vaccination took place within three months of the most recent administration of immunotherapy or within four weeks of the most recent administration of chemotherapy. The production of antibodies to the coronavirus after two vaccinations was chosen as the primary endpoint of the study. A positive response to the virus (seroconversion) was defined as a concentration of more than 10 virus binding antibodies per milliliter of blood serum.
The study showed no difference in response between patients and controls 28 days after the second vaccination. All controls had achieved seroconversion at that point, and so did many patients: 99.3% for immunotherapy, 97.4% for chemotherapy and 100% for chemoimmunotherapy. This was true for seroconversion, but the researchers wanted to know whether the response that had arisen offers protection against getting COVID-19. Based on the ability of the antibodies to neutralize the virus, a value of 300 virus-binding antibodies per milliliter appeared to be the boundary between a sub-optimal and an adequate response.
After the two vaccinations, an adequate response was achieved in 93.1% of the patients who received immunotherapy, 83.8% on chemotherapy and 88.8% on chemo-immunotherapy. In the control group, an adequate response was found in 99.6% of the control subjects. In most patients, the antibody concentration increased after the second vaccination. This indicates that in the group of patients who did not reach the limit value of 300 virus-binding antibodies after two vaccinations, a third vaccination may still give an adequate response. This will be investigated in further research. Only one patient contracted COVID-19 in the period up to 28 days after the second vaccination. No unexpected side effects of the vaccination were seen during the study.
The VOICE study was set up when it was found that COVID-19 can have serious consequences for patients with cancer. This raised the question of whether vaccination against corona is effective and safe for these patients. Chemotherapy can reduce the immune response caused by vaccines, while little is known about immunotherapy, which can potentially enhance the immune response and thereby cause side effects.
The researchers are still monitoring the study participants. They are currently collecting data from six months after vaccination. The response of T cells will also be investigated, as these immune cells can contribute to protection against COVID-19.
The publication ‘A prospective multicentre COVID-19 vaccination trial in patients receiving chemotherapy, immunotherapy, or chemo-immunotherapy for solid tumors’ is expected shortly in Lancet Oncology (in press). Co-researcher Sjoukje Oosting, medical oncologist at the UMCG, will present the research results on Monday 20 September in the ‘presidential symposium’ of the congress of the European Society of Medical Oncology.