Clinical assessment of the Omicron outbreak in Europe and trends in morbidity and mortality from COVID-19 and cancer

ABSTRACT

Background: Whilst patients (pts) with cancer are at increased risk of adverse outcome from Coronavirus disease 2019 (COVID-19), no evidence exists as to the natural history of the SARS-CoV-2 B.1.1.529 (Omicron) variant in this population. Methods: Capitalizing on OnCovid study data (NCT04393974), a European registry that collects data on consecutive patients with cancer and COVID-19, we analysed COVID-19 morbidity and case fatality rates at 14 days (CFR14) 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 (15/12/2020-31/01/2022). Results: By the data lock of 04/02/2022, 3820 consecutive pts were enrolled, 3473 of whom were eligible for this analysis. Among them, 2033 (58.6%), 1075 (30.9%) and 365 (10.5%) were diagnosed during the Pre-vaccination, Alpha-Delta and Omicron phases. Pts diagnosed in the Omicron phase were more likely aged < 65 years (48.6% vs 42.5%, 39.4% p = 0.01), had < 2 comorbidities (61.9% vs 55.6%, 52.1% p = 0.01). They had more advanced-stage tumours (62.1% vs 53.3%, 49.0%, p < 0.01) and were more likely receiving systemic anticancer therapy (SACT) at COVID-19 diagnosis (54.9% vs 43.9%, 39.6%, p < 0.01). Proportions of fully vaccinated/boosted pts were higher in the Omicron phase (33.9%-48.1%) compared to the Alpha-Delta phase (16.6%-2.3%, p < 0.01). Pts diagnosed in the Omicron phase had improved CFR14 (9.0% vs 13.9%, 23.1%, p < 0.01) lower hospitalization rates due to COVID-19 (24.4% vs 41.4%, 56.6%, p < 0.01), lower complications rates (15.3% vs 33.6%, 39.4%, p < 0.01) and reduced need for COVID-19 specific therapy (22.4% vs 43.0%, 65.7% p < 0.01) compared to the Alpha-Delta and pre-vaccinal phase. After adjusting for country of origin, sex, age, comorbidities, tumour stage, status and receipt of SACT at COVID-19, patients diagnosed in the Omicron phase displayed the lowest risk of death at 14 days compared to earlier phases. Similarly, rates of hospitalization and complicated COVID-19 were lowest for Omicron phase. Conclusions: This is the first study to portray the evolution of the SARS-CoV-2 Omicron outbreak in Europe, documenting an improvement in all COVID-19 outcomes compared to earlier phases of the pandemic. Enhanced healthcare capacity, improved disease management, immunization campaigns alongside differential virulence of viral strains are likely contributing to improved outcomes across phases.