“It is incredibly important that patients with cancer all over the world and their treatment specialists know that they can get their COVID-19 vaccine during treatment, and that this 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 – partners of said patients – received a Moderna mRNA vaccine. They received two doses, with the second dose being administered 4 weeks after the first. The first vaccination round took place within three months of the most recent immunotherapy session, or within four weeks of their most recent chemotherapy session. The production of antibodies against COVID-19 after two vaccinations was chosen as the primary endpoint of the trial. A positive response to the virus (seroconversion) was defined as a concentration of over 10 binding antibodies per milliliter of blood serum.
On day 28 after the second vaccine, the study revealed no difference in response between patients and control group. All control subjects had achieved seroconversion, as had most of the patients: 99.3% of the immunotherapy group, 97.4% of the chemotherapy group, and 100% of the chemo-immunotherapy group. While this was true for seroconversion, the researchers also wanted to find out whether the response that had occurred, offered sufficient protection against 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 threshold between a suboptimal and adequate response.
After the two vaccinations, an adequate response occurred in 93.1% of patients receiving immunotherapy, 83.8% of patients receiving chemotherapy, and 88.8% of patients receiving chemo-immunotherapy. An adequate response was found in 99.6% of control subjects. The concentration of antibodies in most patients had increased after their second vaccination, suggesting that a third vaccination may still be able to produce an adequate response in the group of patients who did not reach the necessary 300 virus-binding antibodies after their second vaccination. This will be investigated further in follow-up studies. Only one patient contracted COVID-19 during the 28 days following the second vaccination. No unexpected adverse vaccine side-effects came to light during this study.
The VOICE study was initiated once it became apparent that COVID-19 could have a considerable impact on patients with cancer, which led to the question of whether these patients could safely and effectively get vaccinated against COVID-19. Chemotherapy is known to potentially reduce the immune response caused by vaccines. Little is known about immunotherapy, which could potentially enhance the immune response, potentially causing side effects.
The researchers will continue to closely follow all trial participants. They are currently collecting data from six months after the vaccine, and will also assess T cells response, as these immune cells may contribute to the protection against COVID-19.
The publication, ‘A prospective multicentre COVID-19 vaccination trial in patients receiving chemotherapy, immunotherapy, or chemo-immunotherapy for solid tumours’ is expected to be published in Lancet Oncology (in press). Co-researcher Sjoukje Oosting, medical oncologist at the UMCG, will present the results of the study on Monday, September 20, during the ‘presidential symposium’ of the European Society of Medical Oncology congress.
The VOICE study has been (financially) supported by ZonMw, The Netherlands Organisation for Health Research and Development.