Safety, Immunogenicity, and Efficacy of COVID-19 Vaccines in Radiation-Oncology Patients: A Systematic Review and Meta-Analysis

Abstract

Background/Objectives: The COVID-19 pandemic significantly threatened cancer patients and oncologic care. The rollout of vaccines emerged as a critical milestone, despite the initial lack of evidence regarding their safety and efficacy in this population. This systematic review and meta-analysis evaluate the current evidence on COVID-19 vaccination in patients undergoing radiotherapy (RT). Methods: PubMed, Livivo, Scopus, and Cochrane Library were systematically reviewed for relevant publications on COVID-19 vaccination in the context of radiation oncology, published by 19 April 2024. The treatment effects were calculated as the proportion of seroconverted individuals. Results: A total of 22 studies published between 2021 and 2024 were included, covering various aspects of vaccination, including safety, tolerability, qualitative and quantitative humoral responses, cellular responses, vaccination efficacy, and booster vaccinations. Notably, patients undergoing RT exhibited a high willingness to receive vaccination. Vaccination was overall well tolerated and safe, with a low incidence of side effects, which were primarily mild. The primary meta-analysis showed a seroconversion proportion of 91% [95% CI: 84-96%] overall, with a somewhat higher proportion of 93% in patients receiving RT alone, compared to 90% in patients receiving either RT or RT combined with chemotherapy. Furthermore, immunization during RT led to a sustained increase in antibody titers, with a notable long-term persistence of IgG. Conclusions: COVID-19 vaccines demonstrate excellent safety, immunogenicity, and efficacy in patients receiving RT, who also exhibit a high willingness to be vaccinated. The outcomes observed are comparable to those in healthy controls and superior to those seen in patients receiving other cancer treatments, such as chemotherapy. The vaccination of radiation oncology patients in future pandemics or epidemics is strongly advocated even during active treatment.

Keywords: SARS-CoV-2; booster vaccination; cancer; cellular response; humoral response; immunization; vaccination.

Figure A1

Forest plot of all studies included in the meta-analysis with the pooled result based on inverse-variance weights as a sensitivity analysis. CI = Confidence interval.

Figure A2

Funnel plot of the included studies.

Figure A3

Stratified forest plot with the respective pooled result, discriminating between studies based on the temporal proximity of radiotherapy to vaccination. CI = Confidence interval.

Figure A4

Stratified forest plots with the respective pooled result, discriminating studies based on the study design. CI = Confidence interval.

Figure A5

Stratified forest plot with the respective pooled result, discriminating between studies excluding or not excluding patients with a history of COVID-19 or positive nucleocapsid antibodies prior to vaccination. CI = Confidence interval.

Figure 1

Flow chart of the study conception in detail.

Figure 2

Proportion of seroconversion in patients as reported in the original studies of the meta-analysis, with seroconversion in controls where reported, along with 95% confidence intervals (CIs).

Figure 3

Forest plot of all studies included in the meta-analysis with the pooled result. Each square represents the point estimate with 95% CI for an individual study; The pooled estimate is shown as a diamond. CI = Confidence interval.

Figure 4

Stratified forest plot with the respective pooled result, discriminating between studies comprising patients receiving only radiotherapy and patients additionally receiving chemotherapy. CI = Confidence interval.