NASHVILLE, Tenn. (NewsNation Now) — Brandy Parker-McFadden sits in her Vanderbilt hospital bed, unable to stand.

“Our youngest is like, ‘Are you ever going to walk again?’ We just reassure him this is extremely rare,” she said.

The mother of three received her second Pfizer COVID-19 shot on April 16. Hours later, an unusual sensation started in her legs.

“Then it turned into a horrible neck pain, and it just kept getting worse and worse,” Parker-McFadden said.

Her husband, James, knew something was wrong.

“She was screaming in pain,” he said. “She is one that is pretty stoic. That’s what created the sense of urgency.”

James rushed Brandy to the emergency room at Vanderbilt, and then the unimaginable happened.

“I woke up. I can’t move my arms. I can’t move my legs. So, [James is] freaking out. The doctors are panicking,” Parker-McFadden recalled.

“I’m holding her hand, and her hand is limp throughout the whole thing while she’s screaming in pain,” her husband said. “And all the test results are coming back negative.”

Ten days later, Parker-McFadden is able to move her arms again and wiggle her toes. She will now undergo intensive physical therapy, hoping to walk again.

“I’m going to fight. I’m a fighter,” Parker-McFadden said.

“We take adverse events that are potentially associated with our COVID-19 vaccine, BNT162b2, very seriously,” Pfizer said in a statement to NewsNation affiliate WKRN. “We closely monitor all such events and collect relevant information to share with global regulatory authorities. At this time, our ongoing review has not identified any safety signals with paralysis and the Pfizer-BioNTech COVID-19 vaccine.”

The statement went on to say that medical episodes that have nothing to do with the vaccine could still happen around the time someone gets their shot.

Parker-McFadden is no stranger to showing strength when faced with adversity. She’s turned her diagnosis of epilepsy into a non-profit called My Epilepsy Story. She advocates for women’s health issues, awareness, and support for doctors, which is why she feels sharing this experience is crucial.

“It’s a very rare, rare thing to happen. However, we need to report those rare things because otherwise, we won’t have trust in the medical field,” Parker-McFadden said.

While a formal investigation hasn’t started into Parker-McFadden’s possible reaction, her Vanderbilt medical records read in part, “all of these symptoms are temporally related to the COVID vaccine, raising concern for a vaccine reaction which has been reported to VAERS for investigation.”

VAERS is the U.S. Vaccine Adverse Effects Reporting System. All claims of severe side effects, including death, are sent there for follow-up, but they do not need to be confirmed to be reported.

Parker-McFadden still encourages people to get vaccinated, but she wants them to speak up if they don’t feel well.

“If you’re hesitant, I tell people to call your doctors because [this reaction] is extremely rare,” she said.

Scientists are still cataloging rare potential side effects to COVID-19 vaccines. AstraZeneca’s shot in Europe and Johnson & Johnson’s product in the US were both paused while regulatory panels investigated rare but potentially deadly blood clots.

Both vaccines are now being used again, but patients are advised there is a slim but non-zero chance of that complication.

The Pfizer vaccine was developed in early 2020, and went through three phases of clinical trials in the U.S. with more than 43,000 participants and no reports of paralysis. More than 120 million Pfizer doses have been given in the US so far, according to Our World in Data.

The CDC only suggests avoiding the Pfizer vaccine if you’re allergic to any of its ingredients or you’ve had allergic reactions to vaccines before.

WKRN’s Alex Denis contributed to this report.