(WFLA) — A coroner in the United Kingdom determined that a woman died in March 2021 due to a rare side effect from the AstraZeneca vaccine, according to a report from the BBC this week.

The BBC reported that South Yorkshire Coroner Nicola Mundy listed the cause of death for 34-year-old Kim Lockwood as Vaccine-Induced Thrombotic Thrombocytopenia (VITT), an extremely rare condition.

The UK media outlet said that Lockwood, a mother of two sons, complained of headaches eight days after getting the vaccine. Lockwood thought it was a pre-existing condition was causing her pain, but Mundy said this was not the case.

The BBC said Lockwood sought help at Rotherham Hospital on March 22, 2021, but left after waiting too long.

When she returned the next day, Lockwood had blurred vision and was vomiting. By the middle of the day, she couldn’t even form full sentences.

Seventeen hours after being admitted to the hospital, Lockwood died.

Mundy said Lockwood was “extremely unlucky” and that treatment would not have saved the mother of two from the “sudden and catastrophic” bleed on her brain.

At the time of Lockwood’s death, there was little to link the vaccine to the newly diagnosed syndrome, but medical advancements have allowed doctors to recognize the condition.

The BBC reported that there have been 438 confirmed cases of VITT with 78 deaths as of its report. In comparison, over 24 million people have received the AstraZeneca vaccine.

The American Society of Hematology wrote in January 2022 that VITT is marked by low platelet count and blood clots, usually in the brain or abdomen.

While the condition is extremely rare, it is said to be more prevalent among those who took the AstraZeneca/Johnson and Johnson adenoviral vaccine. Experts said severe symptoms can manifest four to 42 days after getting the shot, although initial symptoms typically occur between six to 14 days.

The ASH said those who have the following symptoms should seek medical evaluation:

  • Severe headache
  • Visual changes
  • Abdominal pain
  • Nausea and vomiting
  • Back pain
  • Shortness of breath
  • Leg pain or swelling
  • Petechiae, easy bruising, or bleeding

If caught, the condition can be treated.