Effect of the Third Dose of Astrazeneca Vaccine on the Ability to Generate Anti-Rbd Antibodies within Two at-Risk Populations, Geriatrics and Health Personnel in The Province of Tucumán

Author(s): Medina Ruiz Luis, Ferre Contreras Miguel, Molina Eliana, Aguilar Mónica, Costas Dardo, Aznar Patricia, Alcorta María Elena, Lara Laura, Barrenechea Guillermo Gabriel, Ortega Eugenia Silvana and Peral de Bruno María de los Ángeles*

This study aims to evaluate the effect on the ability to generate Anti- Anti RBD antibodies (Anti-SAR-CoV 2-Spike-RBD) to the third dose of the AstraZeneca vaccine in two at-risk populations in the Province of Tucumán. Humoral immune responses, assayed by anti-SARS-CoV- 2-Spike-RBD IgG ELISA, were measured in 223 participants, including geriatric patients and healthcare workers, at 0, 14 and 28 days after receiving third dose of the AstraZeneca between October and December 2021 in Tucuman, Argentina. The antibodies title in geriatric patients with and without previous COVID-19 diseases and complete vaccine schedule increased significantly 14 days after receiving the third dose of the AstraZeneca vaccine (p<0.001). When compared Antibody Concentration in geriatric patients with and without a history of COVID-19 14 days postvaccination, the increase in antibodies was higher in those who did not have a previous history of COVID-19 (p<0.05). The antibodies title in healthcare personnel with and without previous COVID-19 diseases and complete vaccination increased significantly 14 days post-vaccination with the third dose of AstraZeneca (p<0.01). There was a negative correlation between age and antibodies titer 14 days after the third dose of COVID vaccine in persons with no history of disease (rs= -0.36, p=0.0001). While persons with a history of COVID-19 did not have a significant correlation (rs= -0.03; p=0.8). The results obtained provide information on antibodies dynamics after the third dose with AstraZeneca in a context of vaccine heterogeneity, indicating the importance of baseline studies of antibodies and hybrid immunity when considering vaccination policies.