March 30, 2021
FDG-avid reactive lymphadenopathy on PET/CT has been reported in patients following COVID-19 vaccinations.1 Reactive lymphadenopathy has been reported in up to 16% of the patients following COVID-19 vaccination with the mRNA (Pfizer/BioNTech, Moderna) vaccines; this side effect has not been reported to date with the AdV vector vaccine (Janssen/Johnson & Johnson).2-5
Some guidelines recommend delay of imaging by 4-6 weeks following the COVID-19 vaccine (NCCN) if it will not affect patient outcomes.2 It is not known at this time if delaying imaging by 6 weeks after the second dose of COVID-19 vaccine is sufficient to ensure resolution of FDG-avid lymphadenopathy.
As with some other vaccinations, such as the influenza vaccine, FDG uptake can also occur at the COVID-19 vaccine injection site. Development of FDG-avid lymphadenopathy is generally ipsilateral to the site of vaccine injection. In addition to the axillary nodes, lymph nodes in the ipsilateral lower internal jugular and supraclavicular stations may also demonstrate FDG uptake. Physicians in the SNMMI COVID-19 Task Force have also anecdotally observed splenomegaly/increased splenic uptake following COVID-19 vaccination. Additional information will be shared on this platform as it becomes available.
The COVID-19 Task Force makes the following recommendations based on the currently available information.
Recognize that FDG-avid lymphadenopathy can occur in the axillary (and possibly lower cervical/supraclavicular) station(s) ipsilateral to the site of injection and can be seen for 4–6 weeks or longer after the most recent dose of vaccine.
Patient questionnaires should be revised to include information about the date(s) and site(s) of vaccination and which vaccine was administered.
For patients with a history of breast and head and neck cancers, the vaccine should be administered in the contralateral arm whenever possible.
1. Doss M, Nakhoda SK, Li Y, Yu JQ. COVID-19 Vaccine-Related Local FDG Uptake. Clin Nucl Med. 2021. Mar 4. doi: 10.1097/RLU.0000000000003634.
2. Recommendations of the NCCN COVID-19 Vaccination Advisory Committee. https://www.nccn.org/covid-19/pdf/COVID-19_Vaccination_Guidance_V2.0.pdf
3. Centers for Disease Control and Prevention. Local Reactions, Systemic Reactions, Adverse Events, and Serious Adverse Events: Pfizer-BioNTech COVID-19 Vaccine. December 13, 2020. Accessed March 6, 2021. https://www.cdc.gov/vaccines/covid-19/info-by-product/pfizer/reactogenicity.html
4. Centers for Disease Control and Prevention. Local Reactions, Systemic Reactions, Adverse Events, and Serious Adverse Events: Moderna COVID-19 Vaccine. December 20, 2020. Accessed March 6, 2021. https://www.cdc.gov/vaccines/covid-19/info-by-product/moderna/reactogenicity.html
5. Centers for Disease Control and Prevention. Local Reactions, Systemic Reactions, Adverse Events, and Serious Adverse Events: Janssen COVID-19 Vaccine. February 26, 2021. Accessed March 6, 2021. https://www.cdc.gov/vaccines/covid-19/info-by-product/janssen/reactogenicity.html
6. Grimm L, Destounis S, Dogan B, et al. Society of Breast Imaging: SBI Recommendations for the Management of Axillary Adenopathy in Patients with Recent COVID-19 Vaccination. Accessed on March 8, 2021. https://www.sbi-online.org/Portals/0/Position%20Statements/2021/SBI-recommendations-for-managing-axillary-adenopathy-post-COVID-vaccination.pdf
7. Lehman CD, Mendoza DP, Succi MD, et al. Unilateral Lymphadenopathy Post COVID-19 Vaccination: A Practical Management Plan for Radiologists Across Specialties. Radiology 2021. Epub March 3, 2021. https://doi.org/10.1016/j.jacr.2021.03.001
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