This Woman's COVID Vaccine Side Effect Led to a Stage 2 Breast Cancer Diagnosis

"As much as COVID sucked-it saved me," Jennifer Mosely said about her cancer diagnosis.

A woman is Iowa said she experienced an unexpected benefit of the COVID-19 vaccine: In her case, getting the vaccine resulted in a stage 2 breast cancer diagnosis.

In April of 2021, Jennifer Moseley noticed a swollen lymph node in her left arm two days after receiving her second dose of the Pfizer vaccine, as Moseley told the Des Moines Register. But because the swollen lymph node was in the same arm where she had the vaccine, she didn't think much about it.

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Breast Cancer Diagnosis

Two days later, the lymph node was still tender. Moseley, who has a family history of breast cancer, realized she hadn't done a breast self-exam in a while. When she did the self-exam, she found a lump the size of a flattened grape in her right breast.

Moseley made an appointment with her doctor to get the lump checked out, which led to a mammogram and a biopsy. Finally, in mid-May, she received a diagnosis: She had stage 2A invasive lobular carcinoma breast cancer, the same cancer that killed her cousin at age 38.

Swollen Lymph Nodes and COVID-19 Vaccines

Swollen lymph nodes can be a side effect of the COVID-19 vaccine and other types of vaccines, infectious disease expert Amesh A. Adalja, MD, senior scholar at the Johns Hopkins Center for Health Security in Maryland, told Health. Lymph nodes are part of your immune system and they can be activated—and swell—when you're exposed to something like a vaccine, said Dr. Adalja.

"Anything that stimulates your immune system can impact the lymph nodes that are near the injection or infection site," said Dr. Adalja.

In February 2022, Radiology published the results of the largest study evaluating swollen lymph nodes after COVID-19 vaccination among patients receiving mammograms. The study showed that the side effect appeared in 44% of the patients. This side effect did not impact mammography outcomes.

Because swollen lymph nodes after COVID-19 vaccination is so common, the Society of Breast Imaging (SBI) initially issued a warning in February 2021, recommending that individuals wait to schedule a mammogram at least four weeks after their COVID-19 vaccine—so they wouldn't think that swollen lymph nodes from the vaccine were a sign of breast cancer.

However, in February 2022, the SBI reversed this recommendation. The SBI's revised recommendations state there is no need to reschedule your next mammogram if it falls close to your vaccination appointment, especially since the side effect can persist for quite a while and has been seen up to 43 weeks after COVID-19 vaccination.

A "Good Coincidence"

Moseley's vaccine didn't cause the lump in her breast, it started a train of thought that motivated her to check herself for signs of cancer. This, said Dr. Adalja, was a "good coincidence."

Moseley noted that she had a routine mammogram scheduled in July 2021. But if she hadn't been vaccinated in April of that year and discovered the swollen lymph node, her cancer could have grown before it was detected. "The COVID-19 shot, I'm gonna say—as much as COVID sucked—it saved me," she told the Des Moines Register.

Moseley had a double mastectomy and breast reconstruction in mid-June of 2021, and is now recovering. Her doctors think they removed all of the cancer, and her family is hopeful that she won't need to undergo chemotherapy.

Moseley encouraged people to check their breasts regularly. "Everyone should be aware that they need to examine their breasts more often," said Moseley.

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