Anti-SARS-CoV-2 spike RBD (receptor-binding domain) IgG antibody levels were monitored in 1643 volunteer healthcare workers of Eginition, Evangelismos, and Konstantopoulio General Hospitals (Athens, Greece), who underwent vaccination with two doses of COVID-19 BNT162b2 mRNA vaccine (Pfizer) and had no history of SARS-CoV-2 infection. Venous blood was collected 20–30 days after the second vaccine dose and anti-RBD IgG levels were determined using CMIA SARS-CoV-2 IgG II Quant (Abbott) on ARCHITECT i System or ADVIA Centaur SARS-CoV-2 IgG (Siemens) on Centaur XP platform. From the total population of 1643 vaccinees (533 M/1110 F; median age = 49; interquartile range-IQR = 40–56), 1636 (99.6%) had anti-SARS-CoV-2 IgG titers above the positivity threshold of the assay used. One-Way ANOVA Kruskal-Wallis H test showed a statistically significant difference in the median of antibody titers between the different age groups (p < 0.0001). Consistently, Spearman’s correlation coefficient (r) for IgGs and age as continuous variables was −0.2380 (p = 1.98 × 10−17). Moreover, antibody titers were slightly higher by 1.2-mean fold (p = 3 × 10−6) in the total female population of the three hospitals (median = 1594; IQR = 875–2584) as compared to males (median = 1292; IQR = 671.9–2188). The present study supports that BNT162b2 vaccine is particularly effective in producing high anti-SARS-CoV-2 IgG levels in healthy individuals, and this humoral response is age- and gender-dependent.

We analyzed the antibody responses of 564 hospital workers in Athens, Greece, after vaccination with two doses of the BNT162b2 (Comirnaty®; BioNTech and Pfizer) mRNA COVID-19 vaccine. A greater antibody increase was observed in women, younger age groups, previously infected individuals and personnel working in COVID-19 clinics. Notably, individuals with a prior COVID-19 infection mounted a significantly higher antibody titer following the first dose than the rest of the population; the same was true for those working in COVID-19 clinics, even without history of previous infection.

BACKGROUND AND AIMS Patients (pts) with end-stage kidney disease (ESRD) may be more vulnerable to infections and may have a suboptimal response to vaccination. Dialysis patient (pt) began to be vaccinated against COVID-19 in February 2021. However, there were many doubts about whether immunization would be effective for them, as these pts have an impaired immune system, and it seems that this population responds poorly to vaccinations. Serum neutralizing antibodies (AbN) rapidly appear after the SARS-CoV-2 infection and the vaccination and are maintained for several months. The emergence of SARS-CoV-2 variants has raised concerns about the breadth of the neutralizing antibody responses. METHOD Serum samples were obtained from 181 patients receiving dialysis. Levels of circulating SARS-CoV-2 anti-spike IgG(S) and anti-nucleocapsid IgG (N) antibodies were quantified using the Abbott Diagnostics SARS-CoV-2 IgG chemiluminescent microparticle immunoassay (Abbott Diagnostics, Abbott Park, IL, USA) on an Abbott Diagnostics Architect i2000 SR and an Alinity analyzer, according to the manufacturer's instructions. Serum neutralizing antibodies (AbN) by commercially available assays (cPass SARS-CoV-2 Neutralization Antibody Detection Kit), at the first and the third months after the vaccination, were identified. RESULTS The IgG-spike Abs had a statistically significant decrease at 3 months after the vaccination in relation to the measurements 1 month after that. AbN had a statistically significant decline at 3 months after the vaccination in relation to the measurements 1 month after. Pts with cardiovascular disease (CD) had significantly lower levels of antibodies than those who did not have CD. Additionally, CD was an aggravating factor in combination with the other comorbidities for the development of antibodies. Pts with a history of malignancy had significantly lower levels of antibodies in relation to those who did not. Those under therapy with antihistamines in the 1st month after the vaccination presented a statistically lower level of the AbNs, but this difference did not exist in the measurements 3 months after vaccination. There was a correlation between the AbNs and the age, also between the time these patients underwent dialysis. Those who had COVID-19 infection presented higher levels of the antibodies AbN/IgG-spiked Ab at 3 months. CONCLUSION It is presented that the IgG-spike Abs and the AbN had a statistically significant decrease at 3 months after the vaccination, which shows the importance of completing vaccination with the third dose after 3 months. Also, it is presented that CD is a risk factor for lower levels of Abs. Randomized clinical trials for COVID-19 vaccines included a few patients with kidney disease; therefore, the vaccine immunogenicity is uncertain in this population.