Convalescent plasma as COVID-19 treatment

A new study from the Journal of the American Medical Association from China (reference below) reports the use of convalescent plasma as a treatment for COVID-19.

What is convalescent plasma? It is a component of blood taken from patients who have recovered from COVID-19, meaning the blood has antibodies to SARS-CoV-19. The theory is that those antibodies from the donor blood can help the recipient recover from the infection (by neutralizing virus in the body).

This isn’t a new approach, it has been used and studied in the H1N1 and H5N1 influenzas, the 2003 SARS outbreak, and ebola.

So what was this study? It was a small “anecdotal” study (not randomized, no control group to compare against) consisting of five patients on ventilators. In short, all 5 patients who received convalescent plasma began experiencing improvement in symptoms within one day, and most were off the ventilator by 9 days.

So could this present a possible treatment for us? It first needs to be studied more rigorously (randomized clinical trial). If it proves effective, it could help provide treatment until a vaccine is developed. In particular, it could benefit the most high-risk patients. The sooner they are transfused (before the body’s humoral response kicks in, meaning the point when the body can make its own antibodies) the better we predict the effect to be. Unfortunately, any type of blood transfusion has significant risks (we call them transfusion reactions), but in sick, high risk patients already on ventilators, the benefits of this treatment outweigh the risks.

The big question is whether this could be a scalable approach, as it depends on donations from patients who have recovered from COVID-19. The answer to that depends on the availability of serologic testing to determine if patients are immune to SARS-CoV-19. If that testing is ramped up, this could present a valuable stopgap measure to help our high-risk patients until medications/treatments and vaccines are available.

Bottom line: we can be hopeful for another potential treatment until we find a medication that can cure)

For more details, here is a breakdown of the study:

  • Design: case series, N=5 COVID-19(+) patients on mechanical ventilation with severe PNA and high viral load (1 patient on ECMO, 2 with wit bacterial and/or fungal PNA)
  • Interventions: 400 mL of convalescent plasma (with IgG and IgM anti-SARS-CoV-19 antibody) received between days 10-22 after admission; patients were also receiving other treatments (lopinavir/ritonavir, interferon, steroids)
    • Plasma donors (status post SARS-CoV-2 infection) symptom-free for at least 10 days
  • Results: respiratory viral load samples decreased and symptoms improved within 1 day
    • Lung findings began improving within 3 days
    • 4 of 5 patients off vent by 9 days
    • 3 of 5 patients discharged after ~50 days (2 remained hospitalized)

Next Questions:

  • Would earlier convalescent plasma administration help improve symptoms sooner (patients waited 10-22 days after admission in this study)
  • Barriers to implementation:
    • Rigorous study validation
    • Blood donation pool (likely at leading edge of viral outbreak); recovered patients could be encouraged to donate blood shortly after hospital discharge
  • Plasma and concentrated H-Ig preparations (plasma from donated blood with high antibody titers; used against hepatitis A/B and and some bacteria, like tetanus and diphtheria) can be frozen for years
    • But these may not be useable next season if the virus mutates sufficiently

Reference: Shen C, Wang Z, Zhao F, et al. Treatment of 5 Critically Ill Patients With COVID-19 With Convalescent Plasma. JAMA. Published online March 27, 2020. doi:10.1001/jama.2020.4783

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