Antibody response to COVID-19 vaccine: A point of view that can help to optimize dose distribution

Comparable antibody levels in heterologous and homologous mRNA COVID-19 vaccination, with superior neutralizing and IgA antibody responses in mRNA homologous boosting

BACKGROUND

Priming with two doses of AZD1222 (Oxford-AstraZeneca; ChAd) followed by a third mRNA vaccine boosting is considered in several countries, yet comparisons between heterologous and homologous booster efficacy remain unexplored.

AIM

To evaluate and contrast the immunogenicity of homologous and heterologous boosting regimens.

METHOD

The study examined antibody responses in 1113 subjects, comprising 895 vaccine-naïve individuals across different vaccination strategies (partial, primary series, heterologous booster, homologous booster) and 218 unvaccinated, naturally infected individuals. Assessments included neutralizing total antibodies (NTAbs), total antibodies (TAbs), anti-S-RBD IgG, and anti-S1 IgA levels.

RESULTS

The study found mRNA vaccines to exhibit superior immunogenicity in primary series vaccination compared to ChAd, with mRNA-1273 significantly enhancing NTAbs, TAbs, anti-S-RBD IgG, and anti-S1 IgA levels (p < 0.001). Both booster types improved antibody levels beyond primary outcomes, with no significant difference in TAbs and anti-S-RBD IgG levels between regimens. However, homologous mRNA boosters significantly outperformed heterologous boosters in enhancing NTAbs and anti-S1 IgA levels, with the BNT/BNT/BNT regimen yielding particularly higher enhancements (p < 0.05).

CONCLUSION

The study concludes that although TAbs and anti-S-RBD IgG antibody levels are similar for both regimens, homologous mRNA boosting outperform heterologous regimen by enhancing anti-S1 IgA and neutralizing antibody levels.

The Evolution of Serological Assays during Two Years of the COVID-19 Pandemic: From an Easy-to-Use Screening Tool for Identifying Current Infections to Laboratory Algorithms for Discovering Immune Protection and Optimizing Vaccine Administration

The emergence of COVID-19 has evolved into a global pandemic, causing an unprecedented public health crisis marked by unprecedented levels of morbidity never seen in the recent past. Considerable research efforts have been made in the scientific community to establish an optimal method to identify severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infections and to understand the induced immune response. This review examined the development of serological tests during the COVID-19 pandemic, considering the factors affecting sensitivity and specificity, which are key to promote an efficient vaccination strategy for public health. The market has witnessed the introduction of various serological tests for the detection of SARS-CoV-2, such as the chemiluminescence immunoassay (CLIA), which emerged as a powerful and rapid tool to monitor the antibody response before and after vaccination or infection. Therefore, developing serological tests by studying antibody trends and persistence is essential for creating long-term strategies. Our analysis underscores the multifaceted applications of serological tests in pandemic management with a focus on the critical insights they provide into antibody dynamics that help in managing the ongoing pandemic and shaping future public health initiatives, providing a basis for optimizing the future response to viral threats.

Follow-Up and Comparative Assessment of SARS-CoV-2 IgA, IgG, Neutralizing, and Total Antibody Responses After BNT162b2 or mRNA-1273 Heterologous Booster Vaccination

BACKGROUND

Priming with ChAdOx1 followed by heterologous boosting is considered in several countries. Nevertheless, analyses comparing the immunogenicity of heterologous booster to homologous primary vaccination regimens and natural infection are lacking. In this study, we aimed to conduct a comparative assessment of the immunogenicity between homologous primary vaccination regimens and heterologous prime-boost vaccination using BNT162b2 or mRNA-1273.

METHODS

We matched vaccinated naïve (VN) individuals (n = 673) with partial vaccination (n = 64), primary vaccination (n = 590), and primary series plus mRNA vaccine heterologous booster (n = 19) with unvaccinated naturally infected (NI) individuals with a documented primary SARS-CoV-2 infection (n = 206). We measured the levels of neutralizing total antibodies (NTAbs), total antibodies (TAbs), anti-S-RBD IgG, and anti-S1 IgA titers.

RESULTS

Homologous primary vaccination with ChAdOx1 not only showed less potent NTAb, TAb, anti-S-RBD IgG, and anti-S1 IgA immune responses compared to primary BNT162b2 or mRNA-1273 vaccination regimens (p < 0.05) but also showed ~3-fold less anti-S1 IgA response compared to infection-induced immunity (p < 0.001). Nevertheless, a heterologous booster led to an increase of ~12 times in the immune response when compared to two consecutive homologous ChAdOx1 immunizations. Furthermore, correlation analyses revealed that both anti-S-RBD IgG and anti-S1 IgA significantly contributed to virus neutralization among NI individuals, particularly in symptomatic and pauci-symptomatic individuals, whereas among VN individuals, anti-S-RBD IgG was the main contributor to virus neutralization.

CONCLUSION

The results emphasize the potential benefit of using heterologous mRNA boosters to increase antibody levels and neutralizing capacity particularly in patients who received primary vaccination with ChAdOx1.

The Antibodies' Response to SARS-CoV-2 Vaccination: 1-Year Follow Up

The use of vaccines has allowed the containment of coronavirus disease 2019 (COVID-19) at a global level. The present work aims to add data on vaccination by evaluating the level of neutralizing antibodies in individuals who have received a three-vaccination series. For this purpose, we ran a surveillance program directed at measuring the level of IgG Abs against the Receptor Binding Domain (RBD) and surrogate virus neutralizing Ab (sVNT) anti-SARS-CoV-2 in the serum of individuals undergoing vaccination. This study was performed on employees from the University of Rome Tor Vergata and healthcare workers from the University Hospital who received the Vaxzevria vaccine (n = 56) and Comirnaty vaccine (n = 113), respectively. After the second dose, an increase in both RBD and sVNT Ab values was registered. In individuals who received the Comirnaty vaccine, the antibody titer was about one order of magnitude higher after 6 months from the first dose. All participants in this study received the Comirnaty vaccine as the third dose, which boosted the antibody response. Five months after the third dose, nearly one year from the first injection, the antibody level was >1000 BAU/mL (binding antibody units/mL). According to the values reported in the literature conferring protection against SARS-CoV-2 infection, our data indicate that individuals undergoing three vaccine doses present a low risk of infection.

Evaluation of autoantibody profile in healthy subjects after mRNA vaccination against COVID-19

BACKGROUND

SARS-CoV-2 severe acute respiratory syndrome has rapidly spread worldwide since 2019. All scientific and technological forces have concentrated towards the formulation of vaccines to contain the disease. In less than one year (December 2020) a first messenger RNA vaccine (Comirnaty, BioNTech/Pfizer) was authorized. However, the research community has wondered about possible side effects on the immune system, given the vaccines administration in phase 4.

AIM

This study aims to evaluate the mRNA vaccine impact on the development of possible positive autoantibody profile in healthcare workers without any previous underlying pathology, after first, second and booster dose of Pfizer vaccine, by determining: circulating immune complexes concentrations (CIC); anti-myeloperoxidase (MPO) and anti-proteinase 3 (PR3) autoantibodies, the presence of antinuclear antibodies (ANA) and subsequent second level tests (extractable nuclear antigen (ENA) screen, double-strand DNA, extractable nuclear antigen (ANA) profile).

METHODS

The subjects were divided according to anti-SARS-CoV-2 IgG RBD antibodies increasing concentrations in: Group I < 10 BAU/ml (N = 114); Group II > 1000 BAU/ml (N = 112); Group III > 2500 BAU/ml (N = 78).

RESULTS

Our data show no autoreactive response changes over time in healthy subjects after vaccination. In fact, evaluation of ANA, CIC, anti-MPO, anti-PR3 and the detection of specific autoantigens, did not display significant variations.

CONCLUSIONS

The results suggest the exclusion of a correlation between the administration of the vaccine and the possible onset of autoimmune disorders. Nevertheless, further investigations will be needed to test for any long-term side effects on an ever-growing population.

Machine Learning Classification of Time since BNT162b2 COVID-19 Vaccination Based on Array-Measured Antibody Activity

Vaccines trigger an immunological response that includes B and T cells, with B cells producing antibodies. SARS-CoV-2 immunity weakens over time after vaccination. Discovering key changes in antigen-reactive antibodies over time after vaccination could help improve vaccine efficiency. In this study, we collected data on blood antibody levels in a cohort of healthcare workers vaccinated for COVID-19 and obtained 73 antigens in samples from four groups according to the duration after vaccination, including 104 unvaccinated healthcare workers, 534 healthcare workers within 60 days after vaccination, 594 healthcare workers between 60 and 180 days after vaccination, and 141 healthcare workers over 180 days after vaccination. Our work was a reanalysis of the data originally collected at Irvine University. This data was obtained in Orange County, California, USA, with the collection process commencing in December 2020. British variant (B.1.1.7), South African variant (B.1.351), and Brazilian/Japanese variant (P.1) were the most prevalent strains during the sampling period. An efficient machine learning based framework containing four feature selection methods (least absolute shrinkage and selection operator, light gradient boosting machine, Monte Carlo feature selection, and maximum relevance minimum redundancy) and four classification algorithms (decision tree, k-nearest neighbor, random forest, and support vector machine) was designed to select essential antibodies against specific antigens. Several efficient classifiers with a weighted F1 value around 0.75 were constructed. The antigen microarray used for identifying antibody levels in the coronavirus features ten distinct SARS-CoV-2 antigens, comprising various segments of both nucleocapsid protein (NP) and spike protein (S). This study revealed that S1 + S2, S1.mFcTag, S1.HisTag, S1, S2, Spike.RBD.His.Bac, Spike.RBD.rFc, and S1.RBD.mFc were most highly ranked among all features, where S1 and S2 are the subunits of Spike, and the suffixes represent the tagging information of different recombinant proteins. Meanwhile, the classification rules were obtained from the optimal decision tree to explain quantitatively the roles of antigens in the classification. This study identified antibodies associated with decreased clinical immunity based on populations with different time spans after vaccination. These antibodies have important implications for maintaining long-term immunity to SARS-CoV-2.

T-Cell Assay after COVID-19 Vaccination Could Be a Useful Tool? A Pilot Study on Interferon-Gamma Release Assay in Healthcare Workers

Background: SARS-CoV-2 T-cells are crucial for long-term protection against reinfection. The aim was to demonstrate the Interferon-gamma Release Assay (IGRA) test could be useful for vaccination monitoring. Methods: In a prospective cohort of 98 vaccinated healthcare workers for SARS-CoV-2, we selected 23 people in low-antibodies (Group 1, N = 8), high-antibodies (Group 2, N = 9), and negative control groups (Group 3, N = 6). SARS-CoV-2-specific humoral and cellular responses were analyzed at 8 months after two doses of Pfizer BioNTech, evaluating anti-RBD (Receptor Binding Domain) and RBD-ACE2 (Angiotensin Converting Enzyme-2) blocking antibodies in sera through a Chemiluminescence Immunoassay (CLIA) and T-cells through the IGRA test in heparinized plasma. Moreover, lymphocyte subtyping was executed by a flow cytometer. Statistical analysis was performed. Results: The data confirmed that RBD and RBD-ACE2 blocking ACE2 antibody levels of Group 1 were significantly lower than Group 2; p < 0.001. However, T-cells showed no significant difference between Group 1 and Group 2. Conclusions: This work suggests the need for new strategies for booster doses administration.

Complete (Humoral and Cellular) Response to Vaccination against COVID-19 in a Group of Healthcare Workers-Assessment of Factors Affecting Immunogenicity

Vaccination is the best way to limit the extent of the COVID pandemic. Knowledge of the duration of the immune response will allow the planning of a vaccination protocol. This study aims to validate the complete (humoral and cellular) immune responses over time in large population groups following the full vaccination of healthcare professionals in real-life conditions and to assess the relationship between antibody levels and T-cell activity in relation to the characteristics of the study group. The samples for the study were obtained from volunteers (staff of two hospitals) on three occasions: before vaccination, T0, then 4–9 weeks after full vaccination (two doses BNT162b2), T1, and 7–9 months after vaccination, T2. The humoral response was investigated by the titre of anti-SARS-CoV-2 IgG antibodies to S1 protein. Assays were performed three times at intervals. The cellular response was assessed in a subgroup of 189 subjects by QuanT-Cell SARS-CoV-2 (IGRA). The assay was performed once. A group of 344 subjects fully vaccinated with the BNT162b2 vaccine were included in the study. The humoral response was observed in 100% of subjects at both 4–7 weeks and 7–9 months, but antibody titres fell by almost 90% in this interval. The cellular response was observed in 94% (177/189) of subjects 7–9 months after the second dose of vaccine. In subjects with a negative cellular response, eight out of 12 smoked. A factor associated with greater immunogenicity of vaccination was past SARS-CoV-2 infection. The administration of full BNT162b2 vaccination (two doses) induces humoral and cellular responses detectable even more than six months after vaccination. Smoking may be a factor associated with impaired cellular response to vaccination.

Evaluation of Natural and Vaccine-Induced Anti-SARS-CoV-2 Immunity: A Comparative Study between Different Groups of Volunteers

(1) Background: The production of anti-SARS-CoV-2 antibodies should help minimize the severity of COVID-19 disease. Our focus was to investigate and compare different vaccination schedules, monitoring circulating S-RBD Ab (antibodies anti—Spike protein—Receptor Binding Domain) levels after administering two doses in naïve patients. Likewise, vaccine-stimulated immunity in naïve and previously infected patients was compared. (2) Methods: We included 392 patients. Sera were evaluated by Elecsys anti-SARS-CoV-2 S. Statistical analyses were conducted by MedCalc and JASP. (3) Results: In COVID-19 patients, the median value of Ab levels was 154 BAU/mL, stable up to 9 months after the infection. From the data observed in vaccinated patients, higher median values were recorded in COVID-19/Pfizer BioNTech (18913 BAU/mL) than in other groups (Pfizer BioNTech: 1841; ChadOx1 961; heterologous vaccination: 2687) BAU/mL. (4) Conclusions: In conclusion, a single booster dose given to previously infected patients raised an antibody response much higher than two doses given to naïve individuals and heterologous vaccination generated a robust persistent antibody response at high levels, steady up to three months after administration.

Blood Antibody Titers and Adverse Reactions after BNT162b2 mRNA Vaccination

This study aimed to measure, considering a prior history of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection (SCV-negative/positive), antibodies titer using Elecsys Anti-SARS-CoV-2 S immunoassay (Roche Diagnostics, Mannheim, Germany), in a serum of healthcare workers (HCW) who received two doses of BNT162b2 vaccines. The local and systemic adverse reactions occurrence was checked with a self-reported questionnaire. A total of 60 SCV-negative HCW showed lower antibody titers than those presented by SCV-positive subjects (n = 7). The highest antibody level was detected 8 days after the second dose of vaccine administration. At the same time, the titer was higher in the SCV2 -positive than the SCV2-negative group and comparable after the first dose in those who became infected to the level after the second dose of those who did not. The local and systemic effects in the SCV2-negative and SCV2-positive groups appeared independent of the vaccine dose. After the second dose, systemic reactions were reported more often than the local adverse effects. Whether no effect was observed or whether the response was local or systemic, the antibody level in a specific group remains constant. These results can be helpful in the improvement of vaccination programs, controlling the occurrence of adverse and long-term effects of the vaccination.