Anti-SARS-CoV-2 antibodies in healthy donor plasma pools and IVIG products

The persistent worsening of the COVID-19 pandemic demands greater efforts for epidemiological surveillance.1, 2 Few studies have assessed the seroprevalence of anti-SARS-CoV-2 antibodies in the general population. These studies have generally had small sample sizes or been restricted to specific, well-defined individuals.3, 4 Given that more than 1000 donors contribute to a plasma pool, the antibody profile of the pool could be considered a representation of the epidemiological status of the population at the time of donation.

In May, 2020, Grifols established a programme for continuous monitoring with ELISA⁵ of the fractionation plasma pools collected in Spain, Germany, Czech Republic, Slovakia, and the USA to track the incorporation of anti-SARS-CoV-2 antibodies into these pools and, consequently, into the resulting batches of intravenous immunoglobulin (IVIG). The first pools testing positive for anti-SARS-CoV-2 antibodies in plasma collected in Spain and the USA were detected from July to early September, 2020 (appendix pp 1–2). From mid-September to November, 2020, most pools in both countries were positive for anti-SARS-CoV-2 antibodies, with increased titres compared with earlier in the pandemic. By contrast, the first plasma pool to test positive for anti-SARS-CoV-2 antibodies in central European countries was detected in mid-November, 2020 (appendix p 3). This difference might reflect a different epidemiological status of the population in Germany, Czech Republic, and Slovakia compared with Spain and the USA.

The anti-SARS-CoV-2 antibody titres measured in the final IVIG products are also shown in the appendix (pp 1–2). Specific anti-SARS-CoV-2 antibodies were first detected in batches of IVIG products manufactured from plasma collected in the USA in September, 2020, with increased titres observed in October, 2020. Plasma from the USA is placed on an inventory hold for 60 days for traceability purposes. In addition, there is a span of 1–2 months between plasma pool preparation and the release of manufactured IVIG.

These results suggest that plasma pools for fractionation might mirror the immunogenic status of the general population regarding SARS-CoV-2. Consequently, anti SARS-CoV-2 antibodies are being increasingly integrated into therapeutic IVIG products and, presumably, into intramuscular and subcutaneous immunoglobulin products. Since these products are indicated for immunodeficient patients and other therapeutic or prophylactic approaches, a close follow-up of the progression of the presence of anti-SARS-CoV-2 antibodies in both plasma pools and IgG products is recommended.