A team of researchers from Japan reported the case of a woman aged 75 years who developed autoimmune hemolytic anemia 2 weeks after receiving the BNT162b2 mRNA COVID-19 vaccination.

“Although vaccination is considered to be very important for suppressing the spread of COVID-19, there have been reports of increasing risk of [idiopathic thrombocytopenic purpura (ITP)] development and deterioration caused by BNT162b2 mRNA COVID-19 vaccination,” wrote Shingo Okuno and the coauthors of the study that was published in the journal Rinsho Ketsueki.

Autoimmune hemolytic anemia is characterized by the body’s immune system mistakenly attacking its own red blood cells. There are different types of autoimmune hemolytic anemia, cold agglutinin disease (CAD) being one of them. Here, autoantibodies against red blood cells are generated in cold temperatures.

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Even though case reports of such a phenomenon have been very limited so far, hematologists should be vigilant of this risk since the number of vaccinated people is rapidly increasing, the team from Tosei General Hospital’s Department of Hematology and Oncology said.

The woman reported in this case study had a history of chemotherapy following surgery to treat her lung adenocarcinoma. She also had a history of Helicobacter pylori eradication from ITP, a blood disorder characterized by an abnormal decrease in the number of platelets in the blood.

Read more about CAD etiology

After she was admitted to the hospital due to anemia, her blood test results showed that she had hemolytic anemia and high levels of lactate dehydrogenase and indirect bilirubin. Researchers found no other obvious trigger for her autoimmune hemolytic anemia other than the BNT162b2 mRNA COVID-19 vaccine. Her condition improved following prednisolone therapy.

It is not known what causes CAD or other types of autoimmune hemolytic anemia. However, underlying conditions like bacterial, viral, and parasitic infections, other autoimmune diseases, and certain types of cancer are known to trigger the condition. 


Okuno S, Hashimoto K, Shimizu R, Takagi E, Kajiguchi T. [Development of autoimmune hemolytic anemia after BNT162b2 mRNA COVID-19 vaccination]. Rinsho Ketsueki. 2021;62(10):1510-1514. doi:10.11406/rinketsu.62.1510