IMMUNE THROMBOCYTOPENIA ONSET AND RELAPSE DURING THE COVID19 PANDEMIC. A MONOCENTER STUDY.

Abstract

BACKGROUND AND OBJECTIVES Several infections and vaccinations can provoke immune thrombocytopenia (ITP) onset or relapse. Information on ITP epidemiology and management during the Covid19 pandemic is scarce. In a large monocenter ITP cohort, we assessed incidence of and risk factors for: 1) ITP onset/relapse after Covid19 vaccination/ infection; 2) Covid19 infection. METHODS Information on date/type of anti-Covid19 vaccine, platelet count before and within 30 days from vaccine and date/grade of Covid19, was collected via phone call or during hematological visits. ITP relapse was defined as a drop in PLT count within 30 days from vaccination, compared to PLT count before vaccination that required a rescue therapy OR a dose increase of an ongoing therapy OR a PLT count <30 x109/L with ≥20% decrease from baseline. RESULTS Between February 2020 and January 2022, 60 new ITP diagnosis were observed (30% related to Covid19 infection or vaccination). Younger and older age were associated to higher probability of ITP related to Covid19 infection (p=0.02) and vaccination (p=0.04), respectively. Compared to Covid19-unrelated ITP, Infection- and vaccine-related ITP had lower response rates (p=0.03) and required more prolonged therapy (p=0.04), respectively. Among the 382 patients with known ITP at pandemic start, 18.1% relapsed; relapse was attributed to Covid19 infection/vaccine in 52.2% of the cases. The risk of relapse was higher in patients with active disease (p<0.001) and previous vaccine-related relapse (p=0.006). Overall, 18.3% of ITP patients acquired Covid19 (severe in 9.9%); risk was higher in unvaccinated patients (p<0.001). CONCLUSIONS All ITP patients should receive ≥1 vaccine dose and laboratory follow-up after vaccination, with case-by-case evaluation of completion of vaccine program if vaccine-related ITP onset/relapse, and with tempestive initiation of antiviral therapy in unvaccinated patients.