A recently published study in the British Journal of Haematology has revealed that the increase in immune thrombocytopenia (ITP) cases are linked to COVID-19 vaccinations. The study found a two-fold increase in ITP cases in 2021 compared to previous years suggesting that the increase is most likely related to COVID-19 vaccinations.

The study presents a single-center analysis of ITP cases during the global high-level COVID-19 vaccination campaign. The research team analyzed all patients presented with ITP at the University Medical Center Hamburg-Eppendorf Haematology and Oncology Department from January 2021 to December 2021.

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The team analyzed baseline clinical characteristics, treatment, and outcome by reviewing electronic medical records. Diagnosis of ITP was conducted based on the German Working Group Definition after excluding the secondary causes. Moreover, COVID-19-vaccine-related (CVR) ITP was diagnosed based on the relapsed thrombocytopenia with temporal proximity to SARS-CoV-2-vaccine injection.

Study results indicated that 40 cases of ITP were detected in 2021 compared to 19, 17, and 18 cases in 2018, 2019, and 2020, respectively. Among the 40 cases, 11 cases (27.5%) were considered COVID-19-vaccine related. Moreover, among the 31 ITP-detected patients, nine patients were considered CVR, 20 as REF, and 2 were associated with a COVID-19 infection. Furthermore, in the CVR group, three patients (33%) reported a preexisting ITP according to anamnesis compared to 4 patients (20%) in the REF group, respectively. Additionally, statistical analysis revealed no differences in treatment and outcome of vaccination and nonvaccination-induced ITP.

“Our study highlights a two-fold increase in ITP cases at our institution in 2021 compared to previous years, most likely related to COVID-19 vaccinations,” the authors noted.

The authors acknowledged several limitations in the study, including the retrospective nature of the study limited to in-patient cases only. The number of severe, in-hospital CVR ITP cases might be underestimated as mild or asymptomatic cases, which were likely missed. Therefore, the actual incidence of CVR ITP was likely higher. Additionally, due to the retrospective approach, there was a lack of a denominator for vaccine-induced ITP compared to previous years.

Furthermore, the limited number of cases in the single-center analysis prevented the identification of any risk factors for new-onset or exacerbating preexisting ITP. Finally, since most patients received outpatient care after discharge, there was no systematic follow-up to determine if ITP persisted under treatment. The authors concluded that further studies are needed to compare the long-term course of CVR ITP.

“To distinguish VITT and CVR ITP, we recommend PF4-antibody testing to exclude VITT in case of symptoms of thrombosis or thrombocytopenia after COVID-19 adenovirus-vectored vaccine administration,”the study authors noted.

COVID-19 vaccinations have been proven to be effective in preventing severe courses and significantly reducing the mortality caused by Severe Respiratory Syndrome Coronavirus 2 (SARS-CoV-2). It is considered that both adenoviral vector and mRNA-based vaccines are generally well-tolerated, but rare cases of new-onset or worsening of ITP have been reported with these vaccines, as well as with active COVID-19 infection. However, there has been no systematic investigation into whether the global COVID-19 vaccination campaigns have led to an increase in vaccine-induced ITP.


Schaefers C, Paulsen FO, Frenzel C, et al. Increased incidence of immune thrombocytopenia (ITP) in 2021 correlating with the ongoing vaccination campaign against COVID-19 in a tertiary center – a monocentric analysis. Br J Haematol. Published online February 15, 2023. Doi: 10.1111/bjh.18686