The Role of Convalescent Plasma in Combating Viral Outbreaks

Humanity recently faced challenges from two new viral outbreaks: a hantavirus outbreak on a cruise ship and the resurgence of Ebola in Africa. Vaccines or antiviral drugs for these viruses are not available, and supportive therapy remains the primary treatment option. Medical experts emphasize quarantine, isolation, and the development of new therapies. However, a potential therapy is already available from survivors: convalescent plasma.

Convalescent Plasma as a Therapy

Convalescent plasma involves using antibodies from recovered individuals to treat those affected by a virus. This therapy has been employed since the early 20th century, including during the 1918 influenza pandemic. In the first year of the COVID-19 pandemic, convalescent plasma was administered to over 600,000 Americans, saving tens of thousands of lives. In 2023, convalescent plasma showed promising results during the West Nile virus outbreak in Israel.

Past outbreaks of hantavirus and Ebola also saw the use of convalescent plasma, though its effectiveness depends on early application and adequately high antibody levels. Historical emergencies made it difficult to confirm efficacy as outbreaks often ended before studies could conclude. During the COVID-19 pandemic, however, numerous clinical trials validated convalescent plasma as an effective therapy when used early.

Challenges and Misunderstandings

Early studies in other countries tested convalescent plasma in patients with late-stage disease, leading to misconceptions about its effectiveness. Later studies confirmed its efficacy when used early and with sufficient antibodies. By 2024, the FDA licensed COVID-19 convalescent plasma for immunosuppressed patients. Today, it stands as the sole antibody therapy for COVID.

Despite its benefits, convalescent plasma faces skepticism within the medical community. Some argue that it is impractical in under-resourced areas due to the need for transfusion services. Yet, over 50 countries, including many poorer nations, used it against COVID. Concerns about standardization can be addressed by measuring antibody content. Its status as an older therapy may contribute to reluctance, despite similar origins with well-established drugs like aspirin.

Overcoming Barriers

Many medical professionals remain unfamiliar with convalescent plasma, primarily used in emergencies and then forgotten. By reviewing extensive evidence from COVID-19, physicians can recognize its potential. Convalescent plasma represents a public good, lacking profit incentives for pharmaceutical development. Its use depends on donors, health authorities, transfusion services, and committed physicians.

Governmental health agencies play a crucial role in logistics for collecting and delivering plasma. During COVID-19, the FDA facilitated the deployment of convalescent plasma, contributing to saving many lives. While robust evidence from randomized trials is ideal, registries can provide essential safety and efficacy data, as demonstrated with convalescent plasma in 2020.

Strategic Use of Convalescent Plasma

Early use is crucial for the success of convalescent plasma, as demonstrated during COVID-19. Administering plasma to outpatients significantly reduced the likelihood of progression to hospitalization. Public health officials can identify survivors willing to donate plasma, which can treat multiple affected individuals, bridging the gap until vaccines, antiviral drugs, and monoclonal antibodies become available.

Dr. Arturo Casadevall, a distinguished professor at Johns Hopkins School of Public Health, played a significant role in deploying convalescent plasma during COVID-19 and has authored over 100 publications on the subject.