Convalescent plasma containing neutralising antibody to SARS-CoV-2 is under investigation for COVID-19 treatment. We report diverse virological characteristics of UK intensive care patients enrolled in the Immunoglobulin Domain of the REMAP-CAP randomised controlled trial that potentially influence treatment outcomes.

SARS-CoV-2 RNA in nasopharyngeal swabs collected pre-treatment was quantified by PCR. Antibody status was determined by spike-protein ELISA. B.1.1.7 was differentiated from other SARS-CoV-2 strains using allele-specific probes or restriction site polymorphism (SfcI) targeting D1118H.

Of 1274 subjects, 90% were PCR-positive with viral loads 118-1.7x10 ¹¹ IU/ml. Median viral loads were 40-fold higher in those seronegative for IgG antibodies (n=354; 28%) compared to seropositives (n=939; 72%). Frequencies of B.1.1.7 increased from