Case Presentation: 73-year-old man was diagnosed with immune thrombocytopenia (ITP) in 2011 and was treated with intravenous immunoglobulin (IVIG), high dose steroid, rituximab and romiplostim to which he responded and subsequently was weaned off of azathioprine and steroid and achieved remission starting 2012. Eight weeks after receiving second dose of Pfizer’s BNT162b2 vaccination, he noted bruising and gum bleeding. His platelet count was 4000/ µL with rest of complete blood count and differential being normal. His peripheral smear was also normal. HIV, Hepatitis panel, vitamin B12, folate, EBV, complete metabolic panel was negative. He was treated with prednisone, IVIG and romiplostim with improvement in his platelet counts to >400,000/ µL. Given his platelet counts, his romiplostim was stopped but 2 weeks after stopping romiplostim, the patient’s platelet decreased gradually to nadir platelet count of < 2000/ µL. He was treated with dexamethasone, IVIG and romiplostim after which his platelet counts again improved to 152 x103/ µL. Given his desire to remain on oral medication he was switched to avatrombopag. Although he had a response to avatrombopag 40 mg daily, he lost response when the dose was lowered to 20 mg and his platelet level decreased again to nadir 3000/µL. He was then placed on immunomodulators (vincristine, sirolimus) and remains on avatrombopag 40 mg daily with IVIG as needed for platelet count less than 20,000/ µL. His platelet count has ranged from 50-170,00 on this treatment and is tolerating treatment well. The temporal relationship between the patient’s presentation post vaccination, other work up of thrombocytopenia being negative and stable course prior to vaccination most likely suggests recurrence of his ITP due to his vaccination.

Discussion: BNT162b2 is a nucleoside-modified mRNA vaccine which encodes surface spike glycoprotein, function of which is to bind and fuse with the host cells and is responsible for formation of humoral and cellular immune responses against SARS-CoV-2 infection.[1] As both SARS-CoV-2 infection and vaccine can trigger autoimmunity, a common pathogenic component such as the spike protein could be responsible for the trigger.[2] Number of cases with thrombocytopenia after receiving mRNA SARS-CoV-2 vaccines reported to the Vaccine Adverse Event Reporting System (VAERS) was around 0.80 per million doses. Since the annual incidence of ITP is 3.3 cases per 100,000 adults,[3] it is quite difficult to differentiate de novo cases of secondary ITP with primary ITP occurring coincidentally after vaccination. Simpson et. al. in their prospective study of vaccinated people in Scotland found out no association with ITP and BNT162b2 vaccine.[4] However, in an analysis of 52 patients with chronic ITP following SARS-CoV-2 vaccination, 12% had a median platelet count drop of 96% and new bleeding symptoms within 2–5 days of vaccination. Most of those patients responded well to corticosteroids +/- IVIg.[5]

Conclusions: Our case highlights the need to be vigilant about SARS-CoV-2 vaccine-induced worsening and recurrence of ITP and their possible management. Events like this are rare and should not be a reason to avoid vaccinating because benefits far outweigh the risk.