SARS-CoV-2 Infection in Patients with a History of VITT

To the Editor:

Vaccine-induced immune thrombotic thrombocytopenia (VITT) is a prothrombotic adverse effect of vaccination against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), an important measure in the prevention of severe coronavirus disease 2019 (Covid-19). VITT is caused by platelet-activating antiplatelet factor 4 (PF4) antibodies of immunoglobulin G class that have been rarely induced by two adenovirus vector–based Covid-19 vaccines, ChAdOx1 nCoV-19 (AstraZeneca) and Ad26.COV2.S (Johnson & Johnson/Janssen).1

All available Covid-19 vaccines generate an immune response against the SARS-CoV-2 spike protein, which arouses concern that VITT may be triggered by cross-reactivity between PF4 and spike protein,2 a view that has been reinforced by the detection of antibodies against PF4 in some patients with Covid-19.3 Despite encouraging in vitro studies that provided no evidence of a link between anti–SARS-CoV-2 and anti-PF4 immune responses,4 investigators could not provide in vivo evidence to exclude such a link due to the lack of an animal model. However, if both immune responses are indeed linked, VITT survivors who subsequently contract Covid-19 should have an increase in anti–PF4 antibodies, potentially even retriggering thrombocytopenia or thrombosis.

Characteristics of 11 Patients with a History of VITT with Subsequent Covid-19.

We performed periodic evaluation of VITT antibody status (study registry, EUPAS45098) in a cohort of 69 patients with a history of VITT who had received an adenovirus vector Covid-19 vaccine. Of these patients, 24 did not receive any subsequent doses of a Covid-19 vaccine; the remaining 45 patients received subsequent doses of a messenger RNA (mRNA) vaccine (either the BNT162b2 [Pfizer–BioNTech] or the mRNA-1273 [Moderna] vaccine). Of these patients, 31 received a second dose and 14 received a third dose. The characteristics of the patients are provided in Table S1 in the Supplementary Appendix, available with the full text of this letter at Of the 69 patients, Covid-19 developed in 11 (16%), all of whom had mild symptoms (Table 1). Covid-19 occurred more frequently in the patients who had received only the adenovirus vector vaccine than in those who had subsequently received one or two doses of an mRNA vaccine (7 of 24 patients [29%] vs. 4 of 45 patients [9%]; P=0.04 by Fisher’s exact test). This lower frequency of symptomatic Covid-19 supports the concept of offering patients with a history of VITT subsequent vaccination with an mRNA-based SARS-CoV-2 vaccine.5

In all the patients who had contracted Covid-19, a follow-up blood sample that was obtained after their recovery was available at a median of 2 weeks after the onset of infection. No major increases in PF4-antibody levels developed after recovery from Covid-19. In most of the patients, repeat optical density readings were lower than those in the last sample obtained before the onset of Covid-19, a finding that was consistent with the inherent natural decline in anti–PF4 antibodies.5 No patient had recurrent thrombocytopenia, new or recurrent thrombosis, or reversion to a positive platelet-activation assay. Our observations provide in vivo evidence that corroborate our previous in vitro findings4 that the immune responses against the SARS-CoV-2 spike protein (induced by Covid-19 or any of the Covid-19 vaccines) and against PF4 (induced in association with VITT) are independent. Our finding that Covid-19 does not restimulate anti–PF4 antibodies in patients with a history of VITT provides further insights into the pathogenesis of this disorder and may be helpful in counseling patients regarding further Covid-19 vaccination with an mRNA vaccine.

Linda Schönborn, M.D.
Sabrina E. Seck, B.Sc.
Thomas Thiele, M.D.
University Medicine Greifswald, Greifswald, Germany

Theodore E. Warkentin, M.D.
McMaster University, Hamilton, ON, Canada

Andreas Greinacher, M.D.
University Medicine Greifswald, Greifswald, Germany

Supported by a grant (374031971–TRR240) from the German Research Foundation. Dr. Schönborn was supported within the Gerhard Domagk Research Program by University Medicine Greifswald. A portion of the results of the study were obtained under a service contract (EMA/2021/17/TDA) with University Medicine Greifswald.

Disclosure forms provided by the authors are available with the full text of this letter at

The views expressed in this letter are those of the authors and do not necessarily reflect those of the European Medicines Agency or one of its Committees or Working Parties.

This letter was published on June 27, 2022, at

  1. 1. Greinacher A, Thiele T, Warkentin TE, Weisser K, Kyrle PA, Eichinger S. Thrombotic thrombocytopenia after ChAdOx1 nCov-19 vaccination. N Engl J Med 2021;384:2092-2101.

  2. 2. Passariello M, Vetrei C, Amato F, De Lorenzo C. Interactions of Spike-RBD of SARS-CoV-2 and platelet factor 4: new insights in the etiopathogenesis of thrombosis. Int J Mol Sci 2021;22:8562-8562.

  3. 3. Brodard J, Kremer Hovinga JA, Fontana P, Studt J-D, Gruel Y, Greinacher A. COVID-19 patients often show high-titer non-platelet-activating anti-PF4/heparin IgG antibodies. J Thromb Haemost 2021;19:1294-1298.

  4. 4. Greinacher A, Selleng K, Mayerle J, et al. Anti-platelet factor 4 antibodies causing VITT do not cross-react with SARS-CoV-2 spike protein. Blood 2021;138:1269-1277.

  5. 5. Schönborn L, Thiele T, Kaderali L, et al. Most anti-PF4 antibodies in vaccine-induced immune thrombotic thrombocytopenia are transient. Blood 2022;139:1903-1907.

Supplementary Material