A team of hematologists and oncologists affiliated with the Bavarian Cancer Research Center (BZKF) conducted a multi-center retrospective analysis of lymphoma patients who contracted COVID-19 at five tertiary care centers in Germany between March 2020 and March 2022. The centers involved span some of the country’s largest university hospitals, including LMU University Hospital Munich, TUM University Hospital, University Hospital Erlangen, University Hospital Regensburg, and University Hospital Augsburg. By pooling anonymized routine clinical data across these institutions, the investigators assembled a cohort large enough and sufficiently granular to compare baseline characteristics, treatment decisions, and clinical outcomes across distinct pandemic waves. The study, led by Stefanie Forkl and Johannes C. Hellmuth of LMU Munich, was published as a brief report in the journal Annals of Hematology and received ethics approval from the medical faculty of LMU Munich.

The central finding is striking in its clarity. In the most recent pandemic wave covered by the analysis — defined as infections occurring after December 27, 2021, when the Omicron variant dominated transmission in Germany — severe COVID-19 courses were recorded in only 4 of 40 lymphoma patients. In the earlier waves, by contrast, 26 of 73 patients experienced severe disease. This difference was statistically significant, with a p-value of 0.03. Mortality followed the same pattern: two of the 40 patients in the late wave died, compared with 14 of the 73 patients infected earlier in the pandemic, a difference that also reached statistical significance at p = 0.039. In proportional terms, the case fatality rate fell from roughly 19 percent in the earlier period to 5 percent in the most recent wave, while the rate of severe disease dropped from about 36 percent to 10 percent.

The authors attribute this improvement not to any single intervention but to the convergence of several protective factors that changed the clinical landscape between 2020 and early 2022. Vaccination coverage among lymphoma patients rose dramatically over the study period. In the final pandemic wave, 88 percent of the infected lymphoma patients had received at least partial vaccination before their SARS-CoV-2 infection, a level of coverage that was essentially absent during the first waves of 2020. This matters even in a population known to mount attenuated antibody responses, because cellular immunity, hybrid immunity from prior infection, and residual humoral responses all contribute to protection against severe disease even when neutralizing antibody titers are suboptimal.

Therapeutic options expanded in parallel. Once infected, 57 percent of the lymphoma patients in the most recent wave were treated with neutralizing monoclonal antibodies, and 35 percent received antiviral agents. Neither class of drug was available in the early months of the pandemic. Monoclonal antibodies such as those directed against the SARS-CoV-2 spike protein offered passive immunization that could compensate for the blunted endogenous antibody responses typical of patients treated with CD20-depleting agents like rituximab, which eliminate the B cells responsible for antibody production. Antiviral drugs, meanwhile, provided a mechanism of protection independent of the patients’ own immune competence, directly inhibiting viral replication during the critical early phase of infection.

The technical significance of this study lies in its wave-by-wave comparison within a single, well-characterized patient population. Many earlier analyses of COVID-19 in hematologic malignancies pooled cases across the entire pandemic or focused on a single center, making it difficult to separate the effects of evolving viral variants, changing patient management, and the natural heterogeneity of lymphoma subtypes. By stratifying outcomes by calendar period and documenting vaccination status and pharmacologic treatment for each case, the BZKF registry provides a longitudinal view of how the intersection of a vulnerable immune state and a shifting pandemic environment determined clinical risk. The consistency of the improvement across both severity and mortality endpoints strengthens the conclusion that the change is real rather than a statistical artifact.

At the same time, the investigators are careful about causal attribution. Because vaccination, monoclonal antibody therapy, antiviral treatment, and the transition to the less virulent Omicron variant all occurred roughly simultaneously, the retrospective design cannot cleanly disentangle the relative contribution of each factor to the observed improvement. A patient infected in early 2022 differed from one infected in 2020 in nearly every relevant dimension: the circulating variant, the immune history, the drugs available, and the accumulated clinical experience of the treating teams. The authors explicitly acknowledge this limitation, noting that while they cannot clearly distinguish the individual effects of each intervention, the aggregate data demonstrate that severity and mortality of COVID-19 in this vulnerable population have recently declined.

For clinicians managing lymphoma patients, the practical implications are nonetheless substantial. The authors conclude that their data largely support a return to pre-pandemic treatment recommendations and protocols for this patient group. During the acute phases of the pandemic, many cancer centers deferred or modified lymphoma therapy, delayed rituximab-containing regimens, and imposed restrictive isolation measures out of concern that immunosuppression would amplify COVID-19 risk. The new findings suggest that such extraordinary caution is no longer proportionate to the residual risk, provided that patients are vaccinated and that breakthrough infections are treated promptly with the antiviral and antibody-based agents now available. This does not mean vigilance can be abandoned entirely — a 5 percent mortality rate among infected patients remains far higher than in the general population — but it marks a meaningful recalibration of the risk-benefit calculus that governed oncology practice during the pandemic’s peak.

The study also underscores the enduring value of disease-specific registries during public health emergencies. The COVID-19-lymphoma registry of the BZKF was built on the infrastructure of an established regional cancer research consortium, allowing rapid, coordinated data collection across five centers without the delays that typically accompany prospective trials in rare populations. Lymphoma patients are heterogeneous — the category encompasses indolent and aggressive B-cell malignancies, T-cell lymphomas, Hodgkin lymphoma, and patients at vastly different points in their treatment trajectories — and only registry-scale efforts can capture enough cases to draw meaningful conclusions about outcomes in subgroups defined by both malignancy and pandemic timing. Similar registry models have proven their worth for other immunocompromised populations and represent a template for future infectious disease threats.

As the pandemic recedes from daily attention, studies like this one serve as a quantitative record of how clinical outcomes evolved in the populations hit hardest. For lymphoma patients in Bavaria and, by extension, in comparable health systems across Europe and North America, the trajectory from 2020 to 2022 was one of genuine improvement: vaccination rates approaching 90 percent, widespread access to passive and antiviral therapies, and a decline in severe disease and death to a fraction of earlier levels. The residual risks are real and warrant continued attention to vaccination schedules, pre-exposure prophylaxis where appropriate, and early treatment of breakthrough infections. But the central message of the BZKF registry is ultimately an encouraging one — that the convergence of immunization, targeted therapeutics, and clinical experience substantially tamed what was once one of the most feared complications facing patients with cancer of the immune system.

Subject of Research: COVID-19 outcomes in lymphoma patients across pandemic waves

Article Title: Change in COVID-19 outcomes in lymphoma patients across pandemic waves: results of the COVID-19-lymphoma registry of the Bavarian Cancer Research Center (BZKF) 2020–2022

Article References: Forkl, S., Freudenberger, F., Jacobs, B., Einhell, S., Hirschbuehl, K., Claus, R., Hellwig, D., Mougiakakos, D., Dreyling, M., Illert, L., Heidegger, S., Weigert, O., & Hellmuth, J. C. (2026). Change in COVID-19 outcomes in lymphoma patients across pandemic waves: results of the COVID-19-lymphoma registry of the Bavarian Cancer Research Center (BZKF) 2020–2022. Annals of Hematology, 105(9), Article 401. https://doi.org/10.1007/s00277-026-07094-x

Image Credits: AI Generated

DOI: 10.1007/s00277-026-07094-x

Keywords: COVID-19, lymphoma, BZKF registry, vaccination, monoclonal antibodies, antiviral therapy, rituximab, CD20-depleting therapy, immunocompromised patients, Omicron variant, Annals of Hematology, hematologic malignancies