The Role of Convalescent Plasma in Combating Viral Outbreaks

Recent months have seen two significant viral outbreaks: a hantavirus outbreak on a cruise ship and a resurgence of Ebola in Africa. There are no vaccines or antiviral treatments for these viruses. Supportive care remains the primary treatment option. Experts discuss quarantine and isolation, but rarely mention a proven therapy from survivors: convalescent plasma.

Survivors of viral diseases generate antibodies that can be transferred to others through convalescent plasma. This therapy has a history dating back to the early 20th century, including its use in the 1918 influenza pandemic. During the first year of the COVID-19 pandemic, over 600,000 Americans received this treatment, saving lives. In 2023, it was used for the West Nile virus outbreak in Israel, showing potential efficacy.

Convalescent plasma has been used in past hantavirus and Ebola outbreaks, but often under less than ideal conditions. The therapy requires early infection intervention and sufficient antibody levels. Historically, its efficacy was challenging to establish due to the emergency nature of outbreaks. However, the extended COVID pandemic allowed for numerous clinical trials, validating the therapy’s effectiveness when used early and with adequate antibody content.

Despite being validated through the COVID-19 experience, convalescent plasma faces skepticism among medical professionals. Some cite logistical challenges, particularly in under-resourced areas. However, over 50 countries, including those with limited resources, utilized it during COVID. There are also concerns about the lack of standardization, as each plasma unit varies in antibody content. However, standardization is possible with proper antibody measurement.

The hesitance to use convalescent plasma may stem from its long history or lack of modern awareness among physicians. Many doctors might overlook its potential without reviewing the substantial evidence available. Convalescent plasma offers no profit to the pharmaceutical industry. Its success depends on the donation of plasma, support from public health authorities, and physicians’ willingness to use it.

Government health agencies play a crucial role in the logistics of plasma collection, testing, and distribution. The FDA’s role during the COVID-19 pandemic was vital in saving lives through plasma deployment. Doctors are cautious with new treatments without solid evidence from randomized trials, but data for safety and effectiveness can come from maintained registries, as shown with plasma in 2020.

Traditionally, convalescent plasma was administered to severely ill patients, but this approach proved ineffective. For antiviral treatments like plasma, early use provides the best results. During COVID, optimal outcomes were seen in outpatients, where plasma reduced hospitalization risk significantly.

Currently, public health officials can identify virus survivors, encourage plasma donations, and test for antibodies to hantavirus and Ebola. One donor can help three patients. Plasma can be frozen for future use, providing an interim treatment until new vaccines and medications are developed.

Arturo Casadevall, M.D., Ph.D., is a distinguished professor and chair at Johns Hopkins School of Public Health. In 2020, he played a significant role in the deployment of convalescent plasma for COVID and has authored numerous papers on the topic.