Total anti-SARS-CoV-2 antibodies measured 6 months after Pfizer-BioNTech COVID-19 vaccination in healthcare workers

Abstract

Background: This study aimed at monitoring the kinetics of serum total anti-SARS-CoV-2 (severe acute respiratory syndrome coronavirus 2) antibodies in a cohort of healthcare workers after voluntary vaccination with Pfizer-BioNTech coronavirus disease 2019 (COVID-19).Methods: The study population consisted of 787 healthcare workers (mean age 44±12 years; 66% females), who received two 30 μg doses of Pfizer-BioNTech COVID-19 vaccine, 3 weeks apart. Venous blood was drawn before the first vaccine dose, immediately before the second vaccine dose, and then at 1, 3 and 6 months after the second vaccine dose. Serological testing employed the total anti-SARS-CoV-2 antibodies measurement with Roche Elecsys Anti-SARS-CoV-2 S chemiluminescent immunoassay.Results: The median serum levels of total anti-SARS-CoV-2 antibodies reached the peak (1762 KU/L) 1 month after the second vaccine dose, but tended to progressively decline at the 3-month (1086 KU/L) and 6-month (802 KU/L) follow-up points. Overall, the values after 3- and 6-months were 37% and 57% lower than the corresponding concentrations measured at the peak. No healthcare worker had total anti-SARS-CoV-2 antibodies below the method-dependent cut-off. The decline compared to the peak was more accentuated in baseline seropositive persons than in those who were baseline seronegative (74% vs. 52%) cohort. The 6-month post-vaccination anti-SARS-CoV-2 antibodies in subjects aged <65 years remained over 2-fold higher than that measured in those aged ≥65 years (813 vs. 343 KU/L). Conclusions: Gradual decline of total anti-SARS-CoV-2 antibodies occurred 6 months after Pfizer-BioNTech COVID-19 vaccination, though values remained higher than the method-dependent cut-off, with no case of seronegativization.

Characterization of the significant decline in humoral immune response six months post-SARS-CoV-2 mRNA vaccination: A systematic review

“…30 Studies looking into the relationship of age and humoral response after undergoing Pfizer-BioNTech vaccination noted an inverse relationship on the antibody titers mounted. 12,31 The studies included in Table 2 highlighted a similar trend.…”

“…Ab titers of females were higher even after humoral decline in all studies (Table 3); however, the percentage decline from the peak was similar for both sexes (Figure 4). 12,25 While it is important to note that overall Ab titers may be influenced by the larger female population cohort (6,238 females vs. 3,128 males) involved in the included studies, this might be attributed to the sex-based difference in humoral immunity which affects vaccine responses. Previous studies indicated that females have a greater humoral response attributed to hormonal differences and X chromosomes leading to biallelic expression of certain genes.…”

“…Among the four journal articles included in this study, two reported that seropositive groups had a larger percent decline in Ab titers from peak compared with seronegative groups. 10,12 This is possibly due to higher peak values making Ab catabolism more pronounced in seropositive groups. 12 Another possible explanation is due to timing, as seropositive groups reach peak Ab titers right after the first dose.…”

“…9 Such vulnerability is correlated to the significant decline in anti-SARS-CoV-2 antibodies (Abs) over time. [10][11][12] This waning humoral response could lead to breakthrough infections, thus highlighting the potential role of serologic testing to assess vaccine immunogenicity and protection efficacy. While the role of T cells and B memory cells from vaccine-induced immunity has yet to be fully elucidated, multiple studies showed that Ab levels directly correlate with risk of vaccine reinfection and breakthrough, with low levels of anti-SARS-CoV-2 IgG in patients with infections correlating with high viral load and duration of viral shedding.…”

Characterization of the significant decline in humoral immune response six months post‐SARS‐CoV‐2 mRNA vaccination: A systematic review

“… 9 Such vulnerability is correlated to the significant decline in anti‐SARS‐CoV‐2 antibodies (Abs) over time. 10 , 11 , 12 This waning humoral response could lead to breakthrough infections, thus highlighting the potential role of serologic testing to assess vaccine immunogenicity and protective efficacy. Although the role of T cells and B memory cells from vaccine‐induced immunity has yet to be fully elucidated, multiple studies showed that Ab levels directly correlate with the risk of vaccine reinfection and breakthrough, with low levels of anti‐SARS‐CoV‐2 immunoglobulin G (IgG) in patients with infections correlating with high viral load and duration of viral shedding.…”