Abstract 504P
Background
Evidence is lacking as to the impact of SARS-CoV-2 Omicron (B.1.1.529) variant in oncological patients.
Methods
Capitalizing on OnCovid study data (NCT04393974), we analysed COVID-19 morbidity and case fatality rate at 28 days (CFR28) of unvaccinated patients across 3 phases defined following the evolution of the pandemic in Europe, according to date of COVID-19 diagnosis: “Pre-vaccination” phase (27/02/2020-30/11/2020), “Alpha-Delta variant” phase (01/12/2020-14/12/2021), “Omicron variant” phase (15/12/2021-31/01/2022).
Results
By the data lock of 04/02/2022, 3820 patients from 37 institutions across 6 countries were entered. Out of 3473 eligible patients, 2033 (58.6%), 1075 (30.9%) and 365 (10.5%) were diagnosed during the Pre-vaccination, Alpha-Delta and Omicron phases. In total 659 (61.3%) and 42 (11.5%) were unvaccinated in the Alpha-Delta and Omicron. Unvaccinated patients across the Omicron, Alpha-Delta and Pre-vaccination phases experienced similar CFR28 (27.5%, 28%, 29%). Following propensity score matching, 42 unvaccinated Omicron patients were matched with 122 and 121 patients from the Pre-vaccination and Alpha-Delta phases respectively, based on country of origin, sex, age, comorbidity burden, primary tumour, cancer stage and status, and the receipt of systemic anticancer therapy at COVID-19. Unvaccinated Omicron patients experienced improved COVID-19 outcomes in comparison to patients diagnosed during the Pre-vaccination phase. Morbidity and mortality were comparable to those of unvaccinated patients diagnosed during the Alpha-Delta phase. Table: 504P
| Omicron vs Pre-vaccination OR (95%CI) | Omicron vs Alpha-Delta OR (95%CI) | |
| CFR 28 | 0.43 (0.19-0.94) | 0.56 (0.25-1.24 |
| Hospitalization | 0.30 (0.12-0.72) | 1.07 (0.46-2.51) |
| Oxygen therapy | 0.39 (0.18-0.84) | 0.77 (0.35-1.66) |
| COVID-19 complications | 0.47 (0.22-1.01) | 0.84 (0.39-1.79) |
Conclusions
Despite time-dependent improvements in outcomes reported in the Omicron phase, patients with cancer remain highly vulnerable to SARS-CoV-2 in absence of vaccinal protection. This study provides unequivocal evidence in support of universal vaccination of patients with cancer as a protective measure against morbidity and mortality from COVID-19.
Clinical trial identification
NCT04393974.
Editorial acknowledgement
Legal entity responsible for the study
The authors.
Funding
Imperial College Biomedical Research Centre.
Disclosure
All authors have declared no conflicts of interest.