Humoral immune response after COVID-19 infection or BNT162b2 vaccine among older adults: evolution over time and protective thresholds


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Date

2022-06

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Journal Article

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Abstract

The objectives of this study were to assess the dynamics of the SARS-CoV-2 anti-RBD-IgG response over time among older people after-COVID-19 infection or vaccination and its comparison with indicative levels of protection.Geriatric patients with SARS-CoV-2 serological test results were included and divided into three groups. A vaccine group (n= 34), a group of natural COVID-19 infection (n = 32), and a group who contracted-COVID-19 less than 15 days after the first injection (n = 17). Eighty-three patients were included; the median age with IQR was 87 (81-91) years. In the vaccine group at 1 month since the first vaccination, the median titer of anti-RBD-IgG was 620 (217-1874) BAU/ml with 87% of patients above the theoretical protective threshold of 141 BAU/ml according to Dimeglio et al. (J Infec. 84(2):248-88, [7]). Seven months after the first vaccination, this titer decreased to 30 (19-58) BAU/ml with9.5% of patients > 141 BAU/ml. In the natural COVID-19 infection group, at 1 month since the date of first symptom onset, the median titer was 798 (325-1320) BAU/ml with86.7% of patients > 141 BAU/ml and fell to 88 (37-385) with 42.9% of patients > 141BAU/ml at 2 months. The natural infection group was vaccinated 3 months after the infection.Five months after the vaccination cycle, the median titer was 2048 (471-4386) BAU/ml with83.3% of patients > 141 BAU/ml. This supports the clinical results describing the decrease in vaccine protection over time and suggests that vaccination after infection canmaintain significantly higher antibody titer levels for a prolonged period of time.

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published

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44 (3)

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1229 - 1240

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Springer

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Subject

Sars-Cov-2; Serology; Anti-RBD IgG; Dynamics; Kinetics

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