COVID arm that appeared in the contralateral upper extremity after mRNA-1273 booster inoculation.

We report the findings of a 60-year-old female patient with metastatic breast cancer who presented with severe edema and neuralgia in the contralateral arm after receiving the third COVID-19 vaccine dose. The patient did not report any reaction to the first two doses of the BNT162b2 (Pfizer-BioNTech) vaccine. However, after a booster dose with the mRNA-1273 (Moderna) vaccine, the patient developed a high fever persisting for one week after the shot, and sequential severe swelling, inflammation, and pain in the contralateral arm lasting for three weeks.