Convalescent Plasma—What is its Perspective in the Treatment of COVID-19 and Other Viral Diseases? A Narrative Review

Abstract Emerging pandemic threats and the complexity of Coronavirus Disease 2019 (COVID-19) management necessitate critical reflection on passive immunization strategies. Convalescent plasma (CP), initially considered a promising therapeutic strategy early in the SARS-CoV-2 pandemic, now occupies a narrower, albeit important, therapeutic niche within the broader treatment landscape. CP has been applied across various viral outbreaks, including viral hemorrhagic fevers such as Ebola and Argentine hemorrhagic fever, severe acute respiratory syndrome (SARS), influenza pandemics, and most recently COVID-19. Given its safety and rapid availability in the absence of specific therapies, CP represents a potentially promising option under certain conditions. Recent large-scale randomized controlled trials and meta-analyses demonstrate that early CP administration within 7 days of symptom onset significantly reduces mortality risk in hospitalized patients, particularly among immunocompromised individuals. However, late administration provides no clear mortality benefit. Recent studies have revealed that conventional plasma units exhibit neutralizing antibody levels comparable to specialized CP units, opening potential for conventional plasma as a more accessible alternative. This finding expands the practical applications of plasma-based therapies. The future clinical significance of CP depends on optimized patient selection, deeper understanding of antibody dynamics, and strategic integration into pandemic preparedness frameworks. CP remains viable for early-stage disease in immunocompromised patients and for emerging viral infections lacking specific therapeutics, including potential novel coronaviruses, henipaviruses, and arenaviruses. Continued research and technological advances in plasma processing will be essential for defining CP’s enduring role in global health security and preparedness for future high-consequence pathogens.