A study evaluated the effectiveness of convalescent plasma therapy in treating 80 SARS patients in Hong Kong between March and May 2003. Patients were given convalescent plasma from recovered SARS patients. Good outcomes were defined as discharge by day 22 after symptom onset, while poor outcomes included death or hospitalization beyond 22 days. Patients who received plasma before day 14 of illness had a higher discharge rate (58.3% vs 15.6%) and lower mortality (6.3% vs 21.9%) compared to those given plasma after day 14. Patients who were PCR positive and seronegative for coronavirus at the time of plasma infusion had a better outcome (66.7% vs 20%). Age was a poor prognostic factor, but the timing of plasma administration and PCR positivity were significant predictors of outcome. No immediate adverse effects were observed. Convalescent plasma was more effective when administered early in the disease course, as viremia peaks in the first week of infection. The study found that early administration of convalescent plasma improved clinical outcomes, while late administration was associated with longer hospital stays and higher mortality. The study had limitations, including lack of randomization and a placebo group. Despite these limitations, the results suggest that convalescent plasma may be beneficial in the early phase of SARS.A study evaluated the effectiveness of convalescent plasma therapy in treating 80 SARS patients in Hong Kong between March and May 2003. Patients were given convalescent plasma from recovered SARS patients. Good outcomes were defined as discharge by day 22 after symptom onset, while poor outcomes included death or hospitalization beyond 22 days. Patients who received plasma before day 14 of illness had a higher discharge rate (58.3% vs 15.6%) and lower mortality (6.3% vs 21.9%) compared to those given plasma after day 14. Patients who were PCR positive and seronegative for coronavirus at the time of plasma infusion had a better outcome (66.7% vs 20%). Age was a poor prognostic factor, but the timing of plasma administration and PCR positivity were significant predictors of outcome. No immediate adverse effects were observed. Convalescent plasma was more effective when administered early in the disease course, as viremia peaks in the first week of infection. The study found that early administration of convalescent plasma improved clinical outcomes, while late administration was associated with longer hospital stays and higher mortality. The study had limitations, including lack of randomization and a placebo group. Despite these limitations, the results suggest that convalescent plasma may be beneficial in the early phase of SARS.