European OnCovid Registry Analysis of COVID-19 Sequelae During Omicron Phase vs Earlier Phases in Patients With Cancer

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In an analysis from the European OnCovid registry reported in The Lancet Oncology, Alessio Cortellini, PhD, and colleagues found that rates of COVID-19 sequelae among patients with cancer were lower during the omicron phase of the pandemic vs the alpha-delta and prevaccination phases, consistent with a higher rate of vaccination during the omicron phase. Overall, booster or two-dose vaccination was associated with a lower risk of sequelae vs partial/no vaccination.

Alessio Cortellini, PhD

Alessio Cortellini, PhD

Study Details 

The study assessed the prevalence of COVID-19 sequelae in patients who survived COVID-19 infection and underwent formal clinical reassessment, with infection categorized by date of diagnosis as falling in:

  • The omicron (B.1.1.529) phase, from December 15, 2021, to January 31, 2022
  • Alpha (B.1.1.7)-delta (B.1.617.2) phase, from December 1, 2020, to December 14, 2021
  • Prevaccination phase, from February 27 to November 30, 2020.

Key Findings

A total of 1,909 eligible patients were included in the analysis. Patients were evaluated at a median of 39 days (interquartile range = 24–68 days) after COVID-19 diagnosis.

In the total cohort, 317 (16.6%, 95% confidence interval [CI] = 14.8%–18.5%) of 1,909 patients had COVID-19 sequelae at first oncologic reassessment.

COVID-19 sequelae were found in 191 (19.1%, 95% CI = 16.4%–22.0%) of 1,000 patients in the prevaccination phase, 110 (16.8%, 95% CI = 13.8–20.3%) of 653 patients in the alpha-delta phase (P = .24 vs prevaccination phase), and 16 (6.2%, 95% CI = 3.5%–10.2%) of 256 patients in the omicron phase (P < .0001 vs prevaccination phase).

Among 458 unvaccinated patients in the alpha-delta phase, sequelae were identified in 84 (18.3%, 95% CI = 14.6%–22.7%). Among 32 unvaccinated patients in the omicron phase, 3 (9.4%, 95% CI = 1.9%–27.3%) had sequelae.

COVID-19 sequelae occurred in 10  (7.4%, 95% CI = 3.5%–13.5%) of 136 vaccine-boosted patients and 18 (9.8%, 95% CI = 5.8%–15.5%) of 183 patients who had two vaccine doses vs 277 (18.5%, 95% CI = 16.5%–20.9%) of 1,489 partially vaccinated/unvaccinated patients (overall P =.0001), including respiratory sequelae in 4.4% and 6.0% vs 9.9% (overall P = .030) and prolonged fatigue in 2.2% and 5.4% vs 7.7% (overall P = .037).

The investigators concluded, “Unvaccinated patients with cancer remain highly vulnerable to COVID-19 sequelae irrespective of viral strain. This study confirms the role of previous SARS–CoV-2 immunisation as an effective measure to protect patients from COVID-19 sequelae, disruption of therapy, and ensuing mortality.”

Dr. Cortellini, of the Department of Surgery and Cancer, Imperial College London, is the corresponding author for The Lancet Oncology article. 

Disclosure: The study was funded by UK National Institute for Health and Care Research Imperial Biomedical Research Centre and the Cancer Treatment and Research Trust. For full disclosures of the study authors, visit

The content in this post has not been reviewed by the American Society of Clinical Oncology, Inc. (ASCO®) and does not necessarily reflect the ideas and opinions of ASCO®.