Clinical Perspective: Greater Magnitude of Reactive Nodal Uptake Following COVID-19 mRNA Vaccination Compared to Traditional Influenza Vaccination

Massachusetts General Hospital, Department of Radiology, Boston, MA, USA

*Corresponding Author: Yingbing Wang, MD, Massachusetts General Hospital, Department of Radiology, 55 Fruit Street, Wht 4-427, Boston, MA 02114, Tel: 617-726-8350; Fax: 617-726-6165; E-mail: [email protected]

Received Date: July 09, 2021

Publication Date: August 25, 2021

ABSTRACT

Background: Increased axillary nodal uptake ipsilateral to site of COVID-19 vaccination on FDG PET is described in the literature.

Purpose: We hypothesize that novel mRNA COVID-19 vaccines induce greater reactive nodal uptake than traditional Influenza vaccines. 

Materials and Methods: We retrospectively reviewed a consecutive series of FDG PET scans performed in patients with recent (<30 days) mRNA-type COVID-19 vaccination during the early vaccination rollout period. The EHR was queried for subset of patients who also had prior FDG PET scans performed within 30 days of intramuscular Influenza vaccination. All relevant FDG PET imaging was reviewed for magnitude of nodal uptake (SUVmax) and assigned a qualitative score of 1, if less than or equal to mediastinum reference, 2 if less than or equal to liver reference, and 3 if greater than liver reference.

Results: During the study period spanning February 22-March 11, 2021, we identified 176 FDG PET scans performed in patients with recent mRNA-type COVID-19 vaccination. 23% of scans showed intense (greater than liver) nodal uptake ipsilateral to the site of injection. All correlative lymph nodes on diagnostic CT remained sub centimeter. 19 patients were identified to have also had prior FDG PET scans performed within 30 days of intramuscular Influenza vaccination; no post-Influenza vaccine FDG PET scans showed any significantly increased axillary nodal uptake.

Conclusion: Our data suggests a significant rate of abnormal ipsilateral nodal uptake following COVID-19 mRNA vaccination and that this rate is likely significantly higher compared to traditional intramuscular Influenza vaccination, possibly due to the highly immunostimulatory effects of the mRNA vaccines.

KEYWORDS: COVID-19; FDG PET; mRNA; Axillary lymph nodes