ABSTRACT
BackgroundSince universal vaccination is a pillar against coronavirus disease 2019 (COVID-19), monitoring anti-SARS-CoV-2 neutralizing antibodies is essential for deciphering post-vaccination immune response. MethodsThree healthcare workers received 30 g BNT162b2 mRNA Covid-19 Vaccine, followed by a second identical dose, 21 days afterwards. Venous blood was drawn at baseline and at serial intervals, up to 63 days afterwards, for assessing total immunoglobulins (Ig) anti-RBD (receptor binding domain), IgG anti-S1/S2, IgG anti-RBD, IgM anti-RBD, IgM anti-N/S1 and IgA anti-S1. ResultsAll subjects were SARS-CoV-2 seronegative at baseline. Total Ig anti-RBD, IgG anti-S1/S2 and IgG anti-RBD levels increased between 91-368 folds until 21 days after the first vaccine dose, then reached a plateau. The levels raised further after the second dose (by [~]30-, [~]8- and [~]8-fold, respectively), peaking at day 35, but then slightly declining and stabilizing [~]50 days after the first dose. IgA anti-S1 levels increased between 7-11 days after the first dose, slightly declined before the second dose, after which levels augmented by [~]24-fold from baseline. The anti-RBD and anti-N/S1 IgM kinetics were similar to that of anti-S1 IgA, though displaying substantially weaker increases and modest peaks, only 4 to 7-fold higher than baseline. Highly significant inter-correlation was noted between total Ig anti-RBD, anti-S1/S2 and anti-RBD IgG (all r=0.99), whilst other anti-SARS-CoV-2 antibodies displayed lower, though still significant, correlations. Serum spike protein concentration was undetectable at all time points. ConclusionsBNT162b2 mRNA vaccination generates a robust humoral immune response, especially involving IgG and IgA, magnified by the second vaccine dose.
ABSTRACT
BackgroundThe ongoing outbreak of coronavirus disease (COVID-19) caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) poses formidable challenges to all health care systems. Serological assays may improve disease management when appropriately used, for better understanding the antibody responses mounted upon SARS-CoV-2 infection and for assessing its real prevalence. Although testing the whole population is impratical, well-designed serosurveys in selected subpopulations in specific risk groups may provide valuable information. Aimwe evaluated the prevalence of SARS-CoV-2 infection in health care workers who underwent molecular testing with reverse transcription real-time polymerase chain reaction (rRT-PCR) in the main hospitals of the Veneto Region by measuring specific antibodies (Abs). Methodsboth IgM and IgG antibodies against SARS-Cov-2 S-antigen and N-protein were measured using a validated chemiluminescent analytical system (CLIA) called Maglumi 2000 Plus (New Industries Biomedical EngineeringCo., Ltd [Snibe], Shenzhen, China) ResultsA total of 8285 health care workers were tested. SARS-CoV-2 specific antibodies (IgM, IgG or both) were detectable in 378 cases (4.6%, 95% CI 4.1-5.0%). Seroconversion was observed in 4.4% women and 5% men, but the difference was not significant. Although detectable antibodies were found in all severe COVID-19 patients (100%), lower seropositivity was found in mild disease (83%) and the lowest prevalence (58%) was observed in asymptomatic subjects. ConclusionSeroprevalence surveys are of utmost importance for understanding the rate of population that has already developed antibodies against SARS-CoV-2. The present study has the statistical power to define precisely the circulation of SARS-CoV-2 in a cohort of health workers in our region, with its prevalence (4.6%) reflecting a relatively low circulation. Symptomatic individuals or those hospitalized for medical care were 100% antibody positive, whilst Abs were only detectable in 58% of asymptomatic carriers.
