Epidemiologic Analysis of Delta Variant SARS-CoV-2 in a Cohort of Lung Transplant Recipients

PURPOSE: Lung transplant (LTx) recipients have increased risk of infection with SARS-CoV-2 and have reduced efficacy from COVID-19 vaccination. The Delta variant of SARS-CoV-2 has increased virulence compared to earlier variants. We hypothesized that LTx recipients would have increased susceptibility to Delta variant infection despite vaccination. METHODS: We performed a retrospective cohort study of 314 LTx recipients followed between 1/1/2020-9/30/2021. Diagnosis of SARS-CoV-2 infection by PCR was recorded; Delta variant comprised >99% of strains from 6/1/2021-9/30/2021. Data regarding COVID-19 vaccination status, symptom development, hospitalization, intubation, and death were collected. RESULTS: Forty-four patients (14%) were diagnosed with COVID-19, 18 (41%) of which were Delta variant. The rate of infection with Delta was 4-fold higher than with earlier strains (Figure, 0.016 vs. 0.004 cases / patient months, p<0.001). Fifteen (83%) patients diagnosed with Delta variant were fully vaccinated at the time of infection (p<0.001). The rate of infection with Delta variant in vaccinated and unvaccinated individuals was similar (0.017/patient months with vaccine, 0.015/patient months without vaccine, p=0.84). The majority (>89%) of patients had respiratory symptoms in both groups. More patients with Delta variant received monoclonal antibody infusions (89% vs. 54%, p=0.021) and fewer patients with Delta variant had resolution of disease (50% vs. 92%, p<0.001). There was a trend towards greater O(2) needs with Delta variant (p=0.07). Hospitalization (38% vs. 23%), intubation (11% vs. 4%), and death (11% vs. 4%) were numerically greater with Delta variant, although not statistically significant. CONCLUSION: The incidence rate of SARS-CoV-2 infection was significantly greater with Delta variant in LTx recipients, despite high prevalence of full vaccination during the Delta wave. Further study in larger cohorts is needed to determine whether booster vaccines can reduce such infectivity.