A Second Dramatic Rise in Seroprevalence Rates of SARS-Cov-2 Antibodies among Adult Healthy Blood Donors in Jordan; Have We Achieved Herd Immunity?

Author(s): Maher A Sughayer, Asem Mansour, Anas Alsughayer, Abeer Al Nuirat, Lina Souan, Rashid Abdel-Razeq, Mahmoud Siag

Background: The seroprevalence rate of SARS-CoV-2 antibodies in healthy blood donors gives an insight into the seroprevalence rate of the infection in the community. We previously reported a dramatic rise in seroprevalence from 0 to 27.4% in blood donors that developed immediately after the first wave of the infection in Jordan.

Objectives: To determine the impact of the second wave of COVID-19 and the vaccination campaign on the seroprevalence rates/p>

Design: A cross sectional observational study representing a 3rd observation in a longitudinal selected population study.

Materials and methods: Excess serological samples from 536 healthy adult blood donors who donated blood during the month of June -2021 were tested using a commercially available quantitative assay for the total antibodies including IgG against the spike (S) protein receptor binding domain (RBD) of the SARS-CoV-2.

Results: 399 (74.4%) of the donors tested positive for the antibodies of whom 69 (17.3%) were confirmed to have been previously infected, 245 (61.4%) have received at least one dose of the vaccine and 123 (30.8%) were neither diagnosed nor vaccinated. The seropositive donors were signifycantly more likely to have been vaccinated or previously infected.

Conclusion: The crude seroprevalence rate of 74.4% among this group of healthy donors may be encouraging in terms of approaching herd immunity, however with predominance of the delta variant and the uncertainty regarding the required level of herd immunity this goal appears to be far from full achievement in Jordan.

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