Skip to main content

Convalescent plasma for COVID-19: the risk of pulmonary embolism should not be underestimated!

Dear Editor,

We read with great interest the elegant editorial of Shankar-Hari et al. [1] regarding the need of randomized studies on the use of convalescent plasma in coronavirus disease (COVID-19) infection. The authors describe safety issues associated with the administration of convalescent plasma, reporting both non-specific (infection, circulatory overload, lung injury) and disease-specific (viral enhancement) side effects of plasma transfusions.

However, it is of utmost importance to highlight that COVID-19 represents a unique scenario where convalescent plasma may be harmful for another essential reason. Indeed, plasma is commonly administered in patients with coagulopathies and/or hemorrhage, as it contains pro-coagulant factors. Importantly, COVID-19 patients are at the other end of coagulative disorders, and it has been consistently shown they develop a pro-thrombotic disease with high-risk of pulmonary embolism [2]. Although laboratory pre-treatment of convalescent plasma with methods aiming at inactivating potential residual virus (such as methylene blue) may decrease also its pro-coagulant effects [3], the presence of even small quantities of coagulation factors may still trigger the coagulation cascade, potentially harming COVID-19 patients. Therefore, it is crucial to ascertain which (if) treatments during the preparation of convalescent plasma have been performed to reduce the amount of coagulation factors. Anyway, we believe that plasma transfusions should be administered thoughtfully in COVID-19 patients to avoid an unnecessary potentiation of their already existing pro-thrombotic state.

In this regard, we do not entirely share the recent enthusiasm generated by a preprint un-reviewed study where the convalescent plasma was administered to over 5000 patients with severe or life-threatening COVID-19 [4]. Indeed, these results should be taken cautiously as the reported low incidence of serious adverse effects refers to an extremely short time-frame of observation (4 h). This period is far too short to fully account for deteriorations due to the progression of the pro-thrombotic state which could potentially generate not only pulmonary embolism but also other systemic events such as cerebral ischemia. Interestingly, the efficacy of convalescent plasma for the treatment of severe influenza has been heavily questioned by a recent meta-analysis published in the journal [5].

To date, several randomized controlled studies are underway (as of the 30th of July on, we found nine studies completed, and 76 currently recruiting). These studies addressing the role of convalescent plasma in COVID-19 should specify the plasma pre-treatment to decrease the amount of coagulation factors and carefully evaluate the incidence of adverse thrombotic events in a timeframe much longer than 4 h.

Availability of data and materials

Not applicable


  1. 1.

    Shankar-Hari M, Estcourt L, Harvala H, Roberts D, Menon DK, Shankar-Hari M, et al. Convalescent plasma to treat critically ill patients with COVID-19: framing the need for randomised clinical trials. Crit Care. 2020;24(1):449.

    Article  Google Scholar 

  2. 2.

    Julien P, Julien G, Morgan C, Erika P, Thibault D, Fanny L, et al. Pulmonary embolism in patients with COVID-19. Circulation. 2020;142(2):184–6.

    Article  Google Scholar 

  3. 3.

    Lozano M, Cid J, Müller TH. Plasma treated with methylene blue and light: clinical efficacy and safety profile. Transfus Med Rev. 2013;27(4):235–40.

    Article  Google Scholar 

  4. 4.

    Joyner MJ, Wright RS, Fairweather D, Senefeld JW, Bruno KA, Klassen SA, et al. Early safety indicators of COVID-19 convalescent plasma in 5,000 patients. J Clin Invest. 2020.,

  5. 5.

    Xu Z, Zhou J, Huang Y, Liu X, Xu Y, Chen S, et al. Efficacy of convalescent plasma for the treatment of severe influenza. Crit Care. 2020;24(1):469.

    Article  Google Scholar 

Download references



Author information




All the authors read and discussed the content of the article by Shankar-Hari et al. FS and MA wrote the draft with the initial idea of discussing the pro-coagulant effects of convalescent plasma. VLR and FO further investigated the issues in the preparation of convalescent plasma. FS and VLR checked the ongoing trials. The authors critically revised and approved the final draft of the manuscript.

Corresponding author

Correspondence to F. Sanfilippo.

Ethics declarations

Ethics approval and consent to participate

Not applicable

Consent for publication

Not applicable

Competing interests

The authors declare that they have no competing interests.

Additional information

Publisher’s Note

Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

Rights and permissions

Open Access This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images or other third party material in this article are included in the article's Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit The Creative Commons Public Domain Dedication waiver ( applies to the data made available in this article, unless otherwise stated in a credit line to the data.

Reprints and Permissions

About this article

Verify currency and authenticity via CrossMark

Cite this article

Sanfilippo, F., La Rosa, V., Oliveri, F. et al. Convalescent plasma for COVID-19: the risk of pulmonary embolism should not be underestimated!. Crit Care 24, 531 (2020).

Download citation