Key Points

  • SARS-CoV-2 vaccines are generally safe in patients with pre-existing ITP but thrombocytopenia exacerbation may occur and requires monitoring

  • Splenectomy and past use of 5 or more therapies predict higher risk of worsening thrombocytopenia in ITP patients post-SARS-CoV-2 vaccine

Cases of de novo immune thrombocytopenia (ITP) - including a fatality - following SARS-CoV-2 vaccination in previously healthy recipients led to studying its impact in pre-existing ITP. In this study, four data sources were analyzed: the Vaccine Adverse Events Reporting System (VAERS) for cases of de novo ITP; a ten-center retrospective study of adults with pre-existing ITP receiving SARS-CoV-2 vaccination; and surveys distributed by the Platelet Disorder Support Association (PDSA, United States) and the United Kingdom (UK) ITP Support Association. Seventy-seven de novo ITP cases were identified in VAERS, presenting with median platelet count of 3 [1-9] x109/L approximately 1-week post-vaccination. Of 28 patients with available data, 26 responded to treatment with corticosteroids and/or intravenous immunoglobulin (IVIG), and/or platelet transfusions. Among 109 patients with pre-existing ITP who received a SARS-CoV-2 vaccine, 19 experienced an ITP exacerbation (any of: ≥50% decline in platelet count, nadir platelet count <30x109/L with >20% decrease from baseline, and/or use of rescue therapy) following the first dose and 14 of 70 after a second dose. Splenectomized persons and those who received 5 or more prior lines of therapy were at highest risk of ITP exacerbation. Fifteen patients received and responded to rescue treatment. In surveys of both 57 PDSA and 43 UK ITP patients, prior splenectomy was associated with worsened thrombocytopenia. ITP may worsen in pre-existing ITP or be identified de novo post-SARS-CoV2-vaccination; both situations responded well to treatment. Proactive monitoring of patients with known ITP, especially those post-splenectomy and with more refractory disease, is indicated.

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