All subjects were COVID-19 na?ve, with no reported COVID-19 infections during the entire study period, which was evidenced by negative SARS-CoV-2 nucleocapsid antibodies (Roche total anti-SARS-CoV-2 nucleocapsid antibody assay) at the beginning of the study and at all time points tested to account for asymptomatic/pauci-symptomatic infections

All subjects were COVID-19 na?ve, with no reported COVID-19 infections during the entire study period, which was evidenced by negative SARS-CoV-2 nucleocapsid antibodies (Roche total anti-SARS-CoV-2 nucleocapsid antibody assay) at the beginning of the study and at all time points tested to account for asymptomatic/pauci-symptomatic infections. post-booster antibody titer (COI 2.11 vs. 0.23, difference 1.63, 95% CI 1.05 to 2.38, < 0.0001). By 180C210 days after the second or third vaccination, Lanopepden total S-Ab/IgG/N-Ab experienced decreased by 68.7/93.8/73.6% Lanopepden vs. 82.8/86.3/79.5%. The half-lives of IgG and N-Ab antibodies were longer after the third vaccination (IgG: 65 vs. 34 days, N-Ab: 99 vs. 78 days). Conclusion: Total S-Ab/IgG/N-Ab showed a greater increase post-booster, with IgG/N-Ab having a longer half-life. Keywords: SARS-CoV-2, booster vaccination, kinetics 1. Introduction Although it has been nearly three years since the start of the COVID-19 pandemic, many countries around the world are still struggling to vaccinate their populations [1]. Vaccination is essential to control the spread of SARS-CoV-2 and has obvious benefits in preventing COVID-19 related morbidity and mortality. Vaccinations were estimated to have prevented 14.4 million deaths during the first year of the pandemic [2] and to have reduced contamination and hospitalization rates across several populations [3]. Even in adolescents aged 12C17 years, a single dose of Pfizer BNT162b2 mRNA vaccine reduced contamination risk by 63.7% after 61C90 days [4]. However, a troubling concern is usually that even after two inoculations, vaccine-induced antibody responses wane over time. One study showed Rabbit polyclonal to HMGCL a drop to 25% residual IgG spike antibody (S-Ab) reactivity after 82.6C89.4 days, regardless of the initial IgG levels [5]. Even total S-Ab levels decreased Lanopepden by 42.7% 79 days after a second dose of the BNT162b2 mRNA COVID-19 vaccine [6]. This is concerning, as reduced antibody levels indicate a reduction in anti-viral protection, with COVID-19-na?ve BNT162b2 vaccinees experiencing a decrease in vaccine effectiveness from 85 to 51% 201 days after their second dose regardless of the vaccination interval [7]. With the introduction of several variants of concern, this can result in an increase in breakthrough infections even in vaccinated individuals [8]. To counter this, several countries have encouraged the use of a third, booster vaccination. Indeed, the CDC [9] now recommends three doses of Pfizer vaccine not just in adults but in children and adolescents as well. The reported overall performance of booster vaccination programs is quite good, even in the current climate where the Omicron variant is usually predominant. In a study of the real-world effectiveness of booster vaccination in the US [10], during a period of Delta predominance, vaccine efficacy (against confirmed COVID-19 contamination) was 76% 180 days after dose two but rose to 94% 14 days after a booster dose of Pfizer vaccine. The booster vaccine also claimed an effectiveness of 82% during a period of Omicron variant predominance, with an efficacy against hospitalization of 90%. Even heterologous booster regimens exhibited impressive results: in a large Chilean study [11], in patients who experienced received an initial two doses of CoronaVac, a booster dose of BNT162b2 vaccine generated an estimated vaccine efficacy of 96.5% with an adjusted vaccine effectiveness of 96.1% against hospitalization 2 weeks after a third dose. However, few studies have reported the extended antibody kinetics after a third dose of vaccine. This would have a bearing on protective public health steps. In our country, healthcare workers were motivated to take a third booster vaccination between October and November 2021. We previously reported the early antibody responses in healthcare workers after their third vaccination [12]. We now statement on their progress after booster vaccinations. 2. Methods 2.1. Study Participants We analyzed 136 subjects who received 3 doses of the Pfizer mRNA vaccine (39 males, 97 females, mean age 43.8 13.5 years) from January 2021 to May 2022. During this period, our country experienced two waves of SARS-CoV-2 variants: Delta from August to November 2021, and Omicron from December 2021 onwards [13]. All subjects were COVID-19 na?ve, with no reported COVID-19 infections during the entire study period, which was evidenced by negative SARS-CoV-2 nucleocapsid antibodies (Roche total anti-SARS-CoV-2 nucleocapsid antibody assay) at the beginning of the study and at all time points tested to account for asymptomatic/pauci-symptomatic infections. Total S-Ab (Roche), IgG S-Ab (Abbott), and neutralizing antibodies (N-Ab) (Snibe) levels were tested at set time points after vaccination up to 210 days post-booster. IgM S-Ab (Abbott) levels.