Recently, two viral outbreaks have captured global attention: a hantavirus incident on a cruise ship and a resurgence of Ebola in Africa. There are currently no vaccines or antiviral drugs available for either virus. The primary treatment option is supportive care. Experts emphasize quarantine, isolation, and the development of new therapies. However, an existing treatment, convalescent plasma, often goes unmentioned.
Convalescent plasma involves transferring antibodies from recovered individuals to those affected by the virus. This method has been a part of infectious disease response since the early 20th century, including during the 1918 influenza pandemic. In the first year of the COVID-19 pandemic, over 600,000 Americans received convalescent plasma, saving many lives. Additionally, during a West Nile virus outbreak in Israel in 2023, convalescent plasma showed promising results.
Both hantavirus and Ebola have seen the application of convalescent plasma in past outbreaks. However, its effectiveness depends on early use and adequate antibody levels. Historically, its efficacy has been hard to prove due to its use under emergency conditions and the quick end of outbreaks. The COVID-19 pandemic provided enough time for conducting numerous clinical trials, leading to its validation as a therapy.
Some early studies during the pandemic tested convalescent plasma in late-stage patients where antibodies proved ineffective, damaging its reputation. Later trials, however, confirmed its success when administered early with sufficient antibodies. The FDA licensed convalescent plasma for immunosuppressed COVID-19 patients in 2024. It remains the sole antibody therapy available for the virus today.
Despite its proven potential, convalescent plasma faces skepticism among medical professionals. They cite challenges such as the need for transfusion services and non-standardized antibody content. However, over 50 countries, including less resourced ones, used it against COVID-19 successfully. Plasma units can be standardized by antibody content to address these concerns.
Convalescent plasma is a public good, lacking commercial interest for development by the pharmaceutical industry. Its success hinges on donors, public health authorities, transfusion services, and committed physicians. Government health agencies play a crucial role in facilitating the logistics of plasma collection, testing, and distribution. The FDA’s involvement during the COVID-19 pandemic saved countless lives through effective convalescent plasma deployment.
Critically, convalescent plasma works best when used early, similar to other antiviral therapies. Its efficacy diminishes when administered to critically ill patients. For optimal outcomes, it should be given to outpatients, reducing their risk of hospitalization by half. Public health authorities could leverage convalescent plasma as an interim solution until vaccines and antiviral drugs become available. Identifying survivors and encouraging plasma donation can help combat hantavirus and Ebola effectively, with one donation potentially aiding three individuals.
Arturo Casadevall, M.D., Ph.D., holds the position of Bloomberg Distinguished Professor and is the Chair of Molecular Microbiology and Immunology at Johns Hopkins School of Public Health. He played a significant role in deploying convalescent plasma for COVID-19 and has published over 100 papers on the subject.
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