Woman in hat wearing hoop earrings

Warning: this article contains images that some readers may find distressing

Patricia is suffering from an unexplained skin condition - but a misunderstanding about what might have caused it set off a chain of events that turned her foot into fodder for anti-vaccine activists.

The picture showed purple and red sores, swollen and oozing with pus.

"Supposedly this is a [vaccine] trial participant," read the message alongside it. "Ready to roll up your sleeve?"

Within a day, those same feet had been mentioned thousands of times on Instagram and Facebook. The picture went viral on Twitter as well.

"See they are trying to deliberately hurt us with the vaccine," one tweet read.

The feet belong to Patricia - a woman in her 30s living in Texas. And it's true - she was a participant in a trial for the Pfizer/BioNTech vaccine that started to be administered on Tuesday.

But this is also true: Patricia never received the actual vaccine. Medical records show that she received a placebo, a small injection of salt water. (Researchers do this as a matter of routine, to compare groups that receive a drug or a vaccine with those who receive the placebo.)

Her illness had nothing to do with injections. But that didn't stop activists twisting her story to advance their own agendas. And on top of the physical pain caused by her condition, Patricia received a wave of online abuse.

From misunderstanding to meme

Patricia says her illness began in late October, when she went on a chilly walk. She noticed feel pain in her left foot. Her husband suggested it might be her shoes rubbing.

But when she got home, she found that her sole had become painfully swollen. A big blister had appeared, much too large to be caused by footwear. It was so big that she had to use one of her daughter's nappies to dress it.

woman holds up foot showing huge blister
image captionPictures of the blisters on Patricia's feet have been used to fuel coronavirus conspiracy theories

When the sole of her other foot also blistered and it became difficult to walk, she visited a number of doctors, who mentioned a number of possible causes.

One of several possibilities they mentioned was fixed drug eruption - a bad skin reaction to a medicine.

Their minds then went to the vaccine trial she was participating in at the time. She had received her second injection five days before the blisters first developed on her feet.

After seeing these doctors, Patricia talked to a relative who was so concerned that she set up a GoFundMe page to raise money for medical bills.

Under America's mostly private health care system, Patricia was already struggling with medical costs due to a back condition. Now she had to take time off from her job as an archival assistant due to her foot sores.

The GoFundMe page made a direct link between the blisters and the vaccine trial. It read: "Patricia... was a volunteer in a COVID-19 vaccine study recently