Abstract
This article aims to summarize the 6-month variation of a vast array of anti-SARS-CoV-2 antibodies in recipients of BNT162b2 mRNA-based vaccination. The study population consisted of 84 baseline SARS-CoV-2 seronegative healthcare employees (median age 45 years, 53.6% females), receiving mRNA-based BNT162b2 primary vaccination cycle. Blood was collected before the first and second BNT162b2 vaccine doses, as well as 1, 3 and 6months afterwards. The serum titers of the following anti-SARS-CoV-2 antibodies were assayed: total anti-RBD (receptor binding domain), anti-spike trimeric IgG, anti-RBD IgG and anti-spike S1 IgA. All antibodies' levels peaked 1month after vaccination, but then displayed a considerable decrease. The median rates of 6-month decline were-95% for IgG anti-SARS-CoV-2 RBD,-85% for IgG anti-SARS-CoV-2 trimeric spike,-73% for IgA anti-SARS-CoV-2 S1 and-56% for total anti-SARS-CoV-2 RBD antibodies, respectively. The median time of seronegativization was estimated at 579days for total anti-SARS-CoV-2 RBD antibodies, 271days for IgG anti-SARS-CoV-2 trimeric spike, 264days for IgG anti-SARS-CoV-2 RBD and 208days for IgA anti-SARS-CoV-2 S1, respectively. The rate of seropositive subjects declined from 98-100% at the peak to 50-100% after 6months. The inter-individual variation of anti-SARS-CoV-2 antibodies reduction at 6months was 3-44% from the peak. The results of this longitudinal serosurvey demonstrate that the titer of anti-SARS-CoV-2 antibodies declined 6months after BNT162b2 vaccination, with median time of IgG/IgA seronegativization estimated between 7 and 9months, thus supporting the opportunity of administering vaccine boosters approximately 5 to 6months after the last dose of the primary vaccination cycle.
Highlights
The ongoing severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2)pandemic outbreak is posing unprecedented challenges to human health, society and economy
The results which have emerged from this longitudinal serosurvey demonstrate that the median titer of a vast array of anti-SARS-CoV-2 antibodies significantly declined 6 months after administration of the second BNT162b2 vaccine dose, with half of vaccine recipients already becoming IgA anti-SARS-CoV-2 S1 seronegative
A significant number of subjects became anti-SARS-CoV-2 RBD IgG seronegative (~30%), whilst the majority (i.e., >98%) maintained titers of anti-SARS-CoV-2 trimeric spike IgG and total anti-SARS-CoV-2 RBD antibodies above the respective positivity thresholds
Summary
The ongoing severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2)pandemic outbreak is posing unprecedented challenges to human health, society and economy. A recent meta-analysis of real-world studies showed that mRNA-based vaccines (e.g., BNT162b2 and mRNA-1273) display better efficacy compared to adenovirus-based (e.g., ChAdOx1 and Ad26.COV2.S) and inactivated (e.g., CoronaVac) vaccines (i.e., 85-100% vs 65-91% efficacy for preventing symptomatic COVID-19) [4] Despite such a remarkable COVID-19 vaccine efficacy, considerably higher than that elicited by influenza vaccine against the risk of developing symptomatic infection [5], waning protection has been clearly demonstrated over time, and 6 months after vaccination, which is leading the way to reinforced vaccination campaigns based on administration of booster COVID-19 vaccine doses to large parts of the population [6]. Conclusions: The results of this longitudinal serosurvey demonstrate that the titer of anti-SARS-CoV-2 antibodies declined 6 months after BNT162b2 vaccination, with median time of IgG/IgA seronegativization estimated between 7-9 months, supporting the opportunity of administering vaccine boosters approximately 6 months after the last dose
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