This plasma contains antibodies specific to a pathogen and can be used therapeutically by providing passive immunity when transfusing it to a newly infected patient with the same condition.
Preparations are typically most effective when given prophylactically or early in the disease course (i.e. until pathogen replication persists or until the infected host's endogenous immune response develops).
[21] Consistent with the general treatment principles of antiviral therapy, the most significant clinical and mortality benefits were noted among patients receiving convalescent serum in the early stages of the disease course.
First identified in 1958, Argentine hemorrhagic fever is a rodent-borne illness caused by the arenavirus Junin that is endemic to the humid pampas of Argentina.
[27] A review and meta-analysis that included eight observational studies (214 total patients) with SARS found a mortality benefit associated with convalescent plasma treatment.
[33] Ebola virus disease was discovered in 1976 when two consecutive outbreaks of fatal hemorrhagic fever occurred in different parts of Central Africa.
[35] Furthermore, two patients with Ebola who were transferred to the U.S. were treated with convalescent plasma, and an experimental small interfering RNA drug, and both survived their infections.
[51] Meta-analyses found that convalescent plasma treatment is associated with a mortality benefit,[52] particularly if it contains high antibody levels, is administered early, and in immunocompromised patients.
[54] In the post-vaccine COVID-19 pandemic, a resurgence in the usage of convalescent plasma occurred starting in the spring of 2022, when the SARS-CoV-2 variant Omicron sublineages proved non-responsive to all anti-spike monoclonal antibody treatments authorized,[55][56] and concerns emerged about contraindications and chronic exposure to small-chemical antivirals which had never been studied in immunocompromised patients at that point.
[59] In the context of the wide deployment of COVID-19 vaccines, a unique product that can be collected from convalescent vaccinees, dubbed “hybrid plasma” or “Vax-plasma” has been of interest;[60] such double status creates heterologous immunity able to cross-react against any SARS-CoV-2 variant so far.
[61] An online petition was launched on April 27, 2022,[62] asking the World Health Organization to revise its guidelines issued in December 2021,[63] which discouraged convalescent plasma usage based on the evidence available until July 2021.
[63] In the European Directorate for the Quality of Medicines and HealthCare guidelines for blood component manufacturing, no monography exists for convalescent plasma yet as of 2022.
Outside clinical trials, the only way thus far to prescribe convalescent plasma is so-called compassionate usage, a procedure which requires authorization by a local ethical committee.