Impact of COVID-19 after lung transplantation: A retrospective multicenter comparison of clinical outcomes in Denmark and Sweden

Abstract

Background: The coronavirus disease-2019 (COVID-19) pandemic posed pronounced challenges in the care of lung transplant (LTx) recipients. Global variations in containment strategies and the introduction of messenger ribonucleic acid (mRNA) vaccines have sparked extensive debate in both scientific and public arenas.

Methods: This retrospective study compared outcomes among LTx recipients in Denmark, which implemented a more restrictive COVID-19 containment strategy, and Sweden, which adopted a less restrictive approach. A total of 318 LTx recipients with at least 1 episode of polymerase chain reaction (PCR)-confirmed COVID-19 were included. Propensity score weighting was applied to balance covariates, and survival outcomes were analyzed using weighted Cox proportional hazards and Kaplan-Meier analyses.

Results: No significant differences in mortality or risk of chronic lung allograft dysfunction (CLAD) were found between countries (hazard ratios [HR] for death, Sweden = 1.49, 95% confidence intervals [CI]: 0.68-3.26, p = 0.314; HR for CLAD, Sweden = 0.63, 95% CI: 0.32-1.25, p = 0.187). Unvaccinated patients had a significantly higher risk of death compared to vaccinated patients (HR = 3.49, 95% CI: 1.46-8.34, p = 0.005), and infections with the original Wuhan strain carried a higher risk than Omicron (HR = 3.59, 95% CI: 1.53-8.44, p = 0.003). CLAD development or progression was not significantly associated with any subgroup.

Conclusions: Despite differences in timing of infections and case load between Sweden and Denmark, clinical outcomes among infected LTx recipients were comparable. mRNA vaccination was strongly associated with improved survival. The results of the current study highlight the importance of continued vaccination efforts and tailored containment strategies in vulnerable populations.

Keywords: COVID-19; Denmark; Sweden; lung transplantation; outcome; sociopolitical approach.

Figure 1

Incidence of the different strains of SARS-CoV-2 over time. Bar plot showing the number of cases of COVID-19 per country over time (orange = Sweden, black = Denmark) as well as the dominating strain of SARS-CoV-2 in the 4 different time periods (Wuhan: January 2020-December 2020, Alpha: January 2021-July 2021, Delta: August 2021-December 2021, Omicron: January 2022-December 2023). COVID-19, coronavirus disease-2019; SARS-CoV-2, severe acute respiratory syndrome coronavirus 2.

Figure 2

No difference in the risk of death between Sweden and Denmark. Kaplan-Meier curve displaying survival probability with 95% CI for patients with COVID-19 in Sweden and in Denmark (blue = Sweden, red = Denmark). There is no statistically significant difference in survival compared between Swedish and Danish patients (p = 0.314). A table with numbers at risk for every 30 days is placed below the curve. CI, confidence interval; COVID-19, coronavirus disease-2019.

Figure 3

Significantly higher risk of death for unvaccinated patients. Kaplan-Meier curve displaying survival probability with 95% CI for patients with COVID-19 before vs after full vaccination (red = unvaccinated, green = vaccinated). There is a statistically significant increase in the risk of death for unvaccinated patients compared to vaccinated patients (p = 0.005). A table with numbers at risk for every 30 days is placed below the curve. CI, confidence interval; COVID-19, coronavirus disease-2019.