DENVER (CBS4) – Getting a COVID-19 vaccine is a relief for most people, but some women are discovering a worrisome side effect from both the Pfizer and Moderna vaccines. The vaccine can cause lymph nodes to swell and that can mirror the signs of breast cancer.

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Even a radiologist who specializes in breast imaging was alarmed.

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“I panicked, I’ll admit, initially,” said Dr. Bridget Rogers, radiologist at Solis Mammography.

She knew swollen lymph nodes could be a sign of breast cancer. So, in early January, she was alarmed.

“I had a big, visible, painful lump,” she told CBS4 Health Specialist Kathy Walsh.

The day before, Rogers had her second COVID-19 shot, the Pfizer vaccine. She knew a possible side effect was enlarged lymph nodes.

“I tried to reassure myself by remembering that this is actually a sign that the vaccine was doing what it’s supposed to do, activating your immune system,” she said.

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Rogers admits she took a look with an ultrasound.

“It’s always different to be on the patient side of the experience,” she said. “It was a sigh of relief the second day when it started to improve rather than worsen.”

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Rogers is not alone. She showed CBS4 the mammograms of another physician who’d gotten a vaccine.

“So this is last year. These are the lymph nodes that are enlarged this year.”

“I’ve been trying to forewarn women ahead of time,” said Dr. Stephanie Miller, a breast surgeon and Medical Director of the Breast Program at Rose Medical Center.

“We do not want to keep anyone from being part of the vaccine process,” said Miller.

She said breast cancer hasn’t slowed down during the pandemic. She tells women to get their mammograms, and let the mammography center know if you’ve recently had a vaccine.

“So that we can have the right explanation for what we’re seeing,” she said.

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Miller said delaying mammograms this year has had consequences.

“Women are developing and presenting with breast cancer a little bit more later stage in the game, and we want to minimize that as much as possible,” Miller said.

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She doesn’t want women to panic. Her message is get a COVID-19 vaccination and a mammogram, both are important for your health.