SARS-CoV-2 antibody seroprevalence rates among Egyptian blood donors around the third wave: Cross-sectional study

Background Seroprevalence studies may provide a more representative situation of the disease burden and population-level immunity in a country. Aim The aim of this study was to determine the prevalence of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) antibodies among asymptomatic blood donors attending the Cairo University blood bank services at various points in time around the third wave. Methods This cross-section study included 3058 eligible blood donors, representing a demographically and socially heterogeneous healthy population and categorized as: Group 1, 954 donors in the period from March 20 to 30/2021; Group 2, 990 donors in the period from June 3 to 10/2021. These two groups were tested for IgG against SARS-CoV-2 nucleocapsid antigen (NC) to detect qualitative reactivity. Group 3, 1114 donors in the period from July 20 to 30/2021 were tested by the SARS-CoV-2 IgG II Quant assay for the quantitative detection of IgG antibodies, including neutralizing antibodies (antispike antibodies). Results Donors' age ranged between 18 and 59 (mean 33.9 +/- 9) years. There was no significant correlation between seroprevalence and gender, area of residence, ABO or Rh blood types, and occupation or education. Antibody prevalence was found to be 13.2% in Group 1, 19.2% in Group 2 (overall 16.2%), and 66% in Group 3. There were only 49 included cases vaccinated against COVID-19. Conclusion We concluded that the significant increasing trend in seroprevalence rates during the third wave, March, June, and July, in Egypt, reflects a high cumulative incidence of seroconversion that mirrored the epidemic curve in its rise, fall, and nadir.