ISRA May 2022

Covid-19 mRNA Vaccination: Age and Immune Status and its Association with Axillary Lymph Node PET/CT Uptake

Yael Eshet 1,2 Michal Eifer 1,2 Noam Tau 1,2 Yousef Alhoubani 1,2 Nayroz Kanana 1,2 Liran Domachevsky 1,2 Jala Shams 2 Nir Keret 2 Malka Gorfine 2
1Department of Diagnostic Imaging, Chaim Sheba Medical Center, Israel
2Sackler School of Medicine, Tel Aviv University, Israel

The worldwide vaccination rollout against COVID-19 resulted in frequent avid axillary lymphadenopathy on PET/CT images. We aimed to assess PET/CT uptake in the deltoid muscle and axillary lymph nodes of patients that received a COVID-19 mRNA-based vaccine, and to evaluate its association with patients’ age and immune status.

Methods: All consecutive adult subjects undergoing PET/CT scans at our center during the first month of a national COVID-19 vaccination rollout (between 23 December 2020 and January 27, 2021) were included. Data regarding clinical status, laterality and time interval from recent COVID-19 mRNA vaccination was prospectively collected and retrospectively analyzed, and correlated with deltoid muscle and axillary lymph nodes uptake.

Results: Of 426 eligible, recently vaccinated, subjects (median age, 67±12 years; 49% female), 377 (88%) underwent PET/CT with 18F-fluorodeoxyglucose (FDG) and positive axillary lymph node uptake was seen in 45% of them. Multivariate logistic regression analysis revealed a strong inverse association between positive FDG uptake in ipsilateral lymph nodes and patients’ age (Odds Ratio [OR]=0.57, 95% CI, 0.45-0.72; p<.001), immunosuppressive treatment (OR=0.37, 95% CI, 0.20-0.64; p=0.003) and presence of hematological disease (OR=0.44, 95% CI, 0.24-0.8; p=0.021). No such association was found for deltoid muscle uptake. The number of days from the last vaccination and the number of vaccination doses were also significantly associated with increased odds of positive lymph nodes uptake.

Conclusion: Following mRNA-based COVID-19 vaccination, a high proportion of patients showed ipsilateral lymph node axillary uptake, which was more common in immunocompetent patients. This information will help recognize PET/CT pitfalls and may hint about the patient’s immune response to the vaccine.