Evaluation of Seropositivity after Standard Doses of Vaccination against SARS-CoV-2 in Early Breast Cancer Patients Receiving Adjuvant Treatment

Background Coronavirus disease 2019 (COVID-19) pandemic affected millions of individuals and patients with cancer are known to be more susceptible. Vaccines against SARS-CoV-2 have been developed and used for patients with cancer, but scarce data is available on their efficacy in patients under active anti-cancer therapies. Materials and Methods In this study, we semi-quantitatively measured the titers of the immunoglobulin G against the anti-spike protein subunit 1 of SARS-CoV-2 after vaccination in early breast cancer patients with concurrent chemotherapy, endocrinal or targeted non-cytotoxic treatments, and no treatments. Results Standard doses of COVID-19 vaccines provided sufficient immune responses in patients with early breast cancer, regardless of the type of anticancer therapies. However, the post-vaccination serum anti-spike antibody titers were significantly lower in the patients under cytotoxic chemotherapy. Conclusion Our study emphasizes the importance of the personalized risk stratification and consideration for booster doses in more vulnerable populations. Implications for Practice In this article, we present rare data on the homogeneous population of patients with early breast cancer under active anti-cancer treatments. The patients showed adequate serologic responses against SARS-CoV-2 virus after standard doses of vaccination without serious adverse events in concurrence with active adjuvant anti-cancer therapy. The patients receiving concurrent cytotoxic chemotherapy, however, have significantly lower serum anti-spike antibody titers than those under non-cytotoxic anti-cancer treatments or without treatments. Selection of the COVID-19 vaccines should be based on personalized risk stratification considering the use of concurrent cytotoxic chemotherapy and the patient’s medical circumstances. Booster doses of vaccination could be considered for the vulnerable population, such as elderly with comorbidities and the single standard dose of vaccination.