Objectives: To describe the immunological responses and clinical outcome of coronavirus (SARS) infected healthcare workers (HCW) who had been administered with convalescent plasma as a treatment.

Methods: Convalescent plasma (500 mL) was obtained from each of three SARS patients and transfused into the three infected HCW. Donors were blood type O and seronegative for hepatitis B and C, HIV, syphilis and human T-cell lymphotropic virus types I and II (HTLV-I and -II). Serum antibody (IgG) titre was >640. Apharesis was performed with a CS 3000 plus cell separator followed by the forming of the convalescent phase plasma. As part of the routine check with donated plasma, the convalescent plasma was confirmed free of residual SARS-CoV by RT–PCR. Serial serum samples obtained from the recipients of the convalescent plasma were collected to undertake real-time quantitative RT–PCR for SARS-CoV for direct measurement of viral concentration. Specific immunoglobulin IgM and IgG concentrations were titrated using an antigen microarray developed in-house.

Results: Viral load dropped from 495 × 10³, 76 × 10³ or 650 × 10³ copies/mL to zero or 1 copy/mL one day after transfusion. Anti-SARS-CoV IgM and IgG also increased in a time-dependent manner following transfusion. All three patients survived. One HCW became pregnant subsequently, delivering 13 months after discharge. Positive anti-SARS-CoV IgG was detected in the newborn. Passive transfer of anti-SARS-CoV antibody from the mother was considered as a possibility.

Conclusions: All infected HCW whose condition had progressed severely and who had failed to respond to the available treatment, survived after transfusion with convalescent plasma.