Omicron: Number of vaccine breakthroughs in cancer patients on the rise, study finds

A total of 3,959 patients who are or have been treated for cancer at University Hospital Vienna and at the Franz Tappeiner Hospital in Merano (Italy) were examined in the study. Eighty-five (85) percent of patients had received at least one vaccination with one of the SARS-CoV-2 vaccines authorised in the EU. Between February 2020 and February 2022, a total of 950 of the 3,959 cancer patients (24 percent) had become infected with the SARS-CoV-2 virus. As the research shows, the number of breakthrough infections increased significantly with the emergence of the Omicron variant in January 2022: 70 percent of infected patients were vaccinated. Thus, the risk of vaccine breakthrough for cancer patients due to Omicron tripled compared with the Delta variant that prevailed between October and December. Breakthrough infections were significantly more common among those who were undergoing systemic treatment than among those without ongoing cancer therapy.

To obtain reasons for the higher rate of breakthrough infections with Omicron compared to Delta, the researchers examined, among other things, the concentration of protective antibodies in the blood in samples from 78 cancer patients and 25 healthy individuals. Strikingly, both in people with solid tumors and blood cancers, there was greatly reduced inhibition of the Omicron variant by specific vaccine antibodies as compared to people without cancer. However, there was also a trend toward shorter hospital stays for vaccinated versus unvaccinated patients. In addition, breakthrough infections only required intensive medical care in rare cases.

Protective measures still important for cancer patients

Matthias Preusser, Head of the Division of Oncology at the Department of Medicine I at MedUni Vienna and University Hospital Vienna, says, "The increasing rates of breakthrough infections and hospitalisations of vaccinated cancer patients associated with Omicron underscore the need for further protective measures not only to effectively combat the ongoing pandemic, but also to prepare for the potential emergence of additional Sars-CoV-2 variants. Vaccines adapted to the particular Sars-CoV-2 variant could help to better protect cancer patients and maintain life-sustaining cancer treatment during the pandemic."

As study director, Preusser conducted the study in cooperation with the Haemato-Oncological Day Clinic at the Franz Tappeiner Hospital in Merano (Italy), the Center for Pathophysiology, Infectiology and Immunology at MedUni Vienna, the Clinical Institute of Laboratory Medicine, the Department of Infections and Tropical Medicine (Department of Medicine I) at MedUni Vienna, the Department of Artificial Intelligence and Human Interfaces and Intelligent Data Analytics Lab Salzburg at the University of Salzburg, and the Faculty of Economics at the University of Klagenfurt.