Anti-SARS-CoV-2 Antibody Development over Four Years in Blood Donors

Area of Science:

• Immunology
• Epidemiology
• Public Health

Background:

• Blood donors serve as a valuable sentinel population for monitoring general population health trends.
• Understanding SARS-CoV-2 seroprevalence is crucial for assessing population immunity and pandemic impact.

Purpose of the Study:

• To survey the seroprevalence of Anti-SARS-CoV-2 antibodies (Anti-NCP and Anti-S) in the Swiss blood donor population.
• To evaluate the blood donor population as a sentinel system for infection surveillance.

Main Methods:

• Cross-sectional seroprevalence survey of blood donors in Switzerland.
• Testing for antibodies against SARS-CoV-2 Nucleocapsid Protein (NCP) and Spike (S) protein.
• Data collection spanned from March 2020 to late 2023.

Main Results:

• Moderate increase in Anti-NCP and Anti-S seroprevalence (~17%) from March 2020 to January 2021.
• Significant rise in seroprevalence observed by May/June 2021 (Anti-NCP 21.6%, Anti-S 59.4%), aligning with initial vaccination.
• Dramatic increase in Anti-NCP (74.6%) by Nov/Dec 2021-Aug 2022, coinciding with Omicron variant spread and mask mandate abolition.
• Seroprevalence reached high levels by end of 2022 (Anti-S 99.0%, Anti-NCP 83.9%) and further increased by end of 2023 (Anti-S 99.8%, Anti-NCP 95.0%).

Conclusions:

• The Swiss blood donor population accurately reflects SARS-CoV-2 infection dynamics, including the impact of vaccination and variants.
• Blood donor surveillance provides a reliable method for tracking infection rates in the general population.