Abstract

Patients with cancer have a higher risk of severe coronavirus disease (COVID-19) and associated mortality than the general population. Owing to this increased risk, patients with cancer have been prioritized for COVID-19 vaccination globally, for both primary and booster vaccinations. However, given that these patients were not included in the pivotal clinical trials, considerable uncertainty remains regarding vaccine efficacy, and the extent of humoral and cellular immune responses in these patients, as well as the risks of vaccine-related adverse events. In this Review, we summarize the current knowledge generated in studies conducted since COVID-19 vaccines first became available. We also highlight critical points that might affect vaccine efficacy in patients with cancer in the future.

Key points

• Vaccination against COVID-19 administered according to current prime–boost concepts is both safe and clinically effective in patients with cancer.
• To date, no reliable correlate of protection that allows the definite deduction of clinical efficacy from immune responses has been established, either in patients with cancer or in the general population.
• Patient-associated factors such as advanced age, haematological malignancy and/or treatment-associated factors such as B cell depletion might all lead to less proficient immune responses following vaccination.
• Future research will determine the necessity of further booster regimens as well as therapeutic options for those who do not benefit from active COVID-19 vaccination.

Conclusions

The development of COVID-19 vaccines has been a massive global effort, leading to a marked reduction in the risk of severe COVID-19 and death. Encouragingly, the available vaccines are safe and effective in patients with cancer, although lower VE has been observed than in those without cancer. A high proportion of patients with solid tumours will develop both humoral and T cell responses following vaccination, although cancer therapies such as chemotherapy can suppress these responses. Patients with haematological malignancies are more vulnerable to breakthrough infections given the reduced VE and often limited immune responses in many of these patients, especially those with B cell malignancies receiving B cell-depleting therapies. Booster vaccines can result in seroconversion in those who were previously seronegative following two vaccine doses. This observation indicates that regular booster vaccines might be effective for immunocompromised patients with cancer. Additionally, high vaccination rates in the community, especially among the families of vulnerable patients and in clinical care settings, will help protect those with impaired vaccine responses.