Sputnik V vaccine elicits seroconversion and neutralizing capacity to SARS-CoV-2 after a single dose

Humoral and cellular response of two different vaccines against SARS-CoV-2 in a group of healthcare workers: An observational study

On March 13, 2021, Tunisia started a widespread immunization program against SARS-CoV-2 utilizing different vaccinations that had been given emergency approval. Herein, we followed prospectively a cohort of participant who received COVID-19 vaccine (Pfizer BioNTech and Sputnik-Gameleya V). The goal of this follow-up was to define the humoral and cellular immunological profile after immunization by assessing neutralizing antibodies and IFN- γ release. 26 vaccinated health care workers by Pfizer BioNTech (n=12) and Sputnik-Gameleya V (n=14) were enrolled from June to December 2021 in Military hospital of Tunis. All consenting participants were sampled for peripheral blood after three weeks of vaccination. The humoral response was investigated by the titer of anti-SARS-CoV-2 immunoglobulin G (IgG) antibodies to S1 protein. The CD4 and CD8 T cell responses were evaluated by the QuantiFERON® SARS-CoV-2 (Qiagen® Basel, Switzerland). Regardless the type of vaccine, the assessment of humoral and cellular response following vaccination showed a strong involvement of the later with expression of IFN-γ as compared to antibodies secretion. Moreover, we showed that people with past SARS-CoV-2 infection developed high levels of antibodies than those who are not previously infected. However, no significant difference was detected concerning interferon gamma (IFN-γ) expression by CD4 and CD8 T cells in health care worker (HCW) previously infection or not with COVID-19 infection. Analysis of immune response according to the type of vaccine, we found that Pfizer BioNTech induced high level of humoral response (91.66%) followed by Sputnik-Gameleya V (64.28%). However, adenovirus vaccine gave a better cellular response (57.14%) than mRNA vaccine (41.66%). Regarding the immune response following vaccine doses, we revealed a significant increase of neutralizing antibodies and IFN-γ release by T cells in patients fully vaccinated as compared to those who have received just one vaccine. Collectively, our data revealed a similar immune response between Pfizer BioNTech and Sputnik-Gameleya V vaccine with a slight increase of humoral response by mRNA vaccine and cellular response by adenovirus vaccine. It's evident that past SARS-CoV-2 infection was a factor that contributed to the vaccination's increased immunogenicity. However, the administration of full doses of vaccines (Pfizer BioNTech or Sputnik-Gameleya V) induces better humoral and cellular responses detectable even more than three months following vaccination.

What makes SARS-CoV-2 unique? Focusing on the spike protein

Severe acute respiratory syndrome-related coronavirus 2 (SARS-CoV-2) seriously threatens public health and safety. Genetic variants determine the expression of SARS-CoV-2 structural proteins, which are associated with enhanced transmissibility, enhanced virulence, and immune escape. Vaccination is encouraged as a public health intervention, and different types of vaccines are used worldwide. However, new variants continue to emerge, especially the Omicron complex, and the neutralizing antibody responses are diminished significantly. In this review, we outlined the uniqueness of SARS-CoV-2 from three perspectives. First, we described the detailed structure of the spike (S) protein, which is highly susceptible to mutations and contributes to the distinct infection cycle of the virus. Second, we systematically summarized the immunoglobulin G epitopes of SARS-CoV-2 and highlighted the central role of the nonconserved regions of the S protein in adaptive immune escape. Third, we provided an overview of the vaccines targeting the S protein and discussed the impact of the nonconserved regions on vaccine effectiveness. The characterization and identification of the structure and genomic organization of SARS-CoV-2 will help elucidate its mechanisms of viral mutation and infection and provide a basis for the selection of optimal treatments. The leaps in advancements regarding improved diagnosis, targeted vaccines and therapeutic remedies provide sound evidence showing that scientific understanding, research, and technology evolved at the pace of the pandemic.

RBD-specific antibody response after two doses of different SARS-CoV-2 vaccines during the mass vaccination campaign in Mongolia

The SARS-CoV-2 vaccination campaign began in February 2021 and achieved a high rate of 62.7% of the total population fully vaccinated by August 16, 2021, in Mongolia. We aimed to assess the initial protective antibody production after two doses of a variety of types of SARS-CoV-2 vaccines in the Mongolian pre-vaccine antibody-naïve adult population. This prospective study was conducted from March-April to July-August of 2021. All participants received one of the four government-proposed COVID-19 vaccines including Pfizer/BioNTech (BNT162b2), AstraZeneca (ChAdOx1-S), Sinopharm (BBIBP-CorV), and Sputnik V (Gam-COVID-Vac). Before receiving the first shot, anti-SARS-CoV-2 S-RBD human IgG titers were measured in all participants (n = 1833), and titers were measured 21-28 days after the second shot in a subset of participants (n = 831). We found an overall average protective antibody response of 84.8% (705 of 831 vaccinated) in 21-28 days after two doses of the four types of COVID-19 vaccines. Seropositivity and titer of protective antibodies produced after two shots of vaccine were associated with the vaccine types, age, and residence of vaccinees. Seropositivity rate varied significantly between vaccine types, 80.0% (28 of 35) for AstraZeneca ChAdOx1-S; 97.0% (193 of 199) for Pfizer BNT162b2; 80.7% (474 of 587) for Sinopharm BBIBP-CorV, and 100.0% (10 of 10) for Sputnik V Gam-COVID-Vac, respectively. Immunocompromised vaccinees with increased risk for developing severe COVID-19 disease had received the Pfizer vaccine and demonstrated a high rate of seropositivity. A high geometric mean titer (GMT) was found in vaccinees who received BNT162b2, while vaccinees who received ChAdOx1-S, Sputnik V, and BBIBP-CorV showed a lower GMT. In summary, we observed first stages of the immunization campaign against COVID-19 in Mongolia have been completed successfully, with a high immunogenicity level achieved among the population with an increased risk for developing severe illness.

Phenotypic Changes in T and NK Cells Induced by Sputnik V Vaccination

A highly effective humoral immune response induced by the Sputnik V vaccine was demonstrated in independent studies, as well as in large-scale post-vaccination follow-up studies. However, the shifts in the cell-mediated immunity induced by Sputnik V vaccination are still under investigation. This study was aimed at estimating the impact of Sputnik V on activating and inhibitory receptors, activation and proliferative senescence markers in NK and T lymphocytes. The effects of Sputnik V were evaluated by the comparison of PBMC samples prior to vaccination, and then three days and three weeks following the second (boost) dose. The prime-boost format of Sputnik V vaccination induced a contraction in the T cell fraction of senescent CD57⁺ cells and a decrease in HLA-DR-expressing T cells. The proportion of NKG2A⁺ T cells was down-regulated after vaccination, whereas the PD-1 level was not affected significantly. A temporal increase in activation levels of NK cells and NKT-like cells was recorded, dependent on whether the individuals had COVID-19 prior to vaccination. A short-term elevation of the activating NKG2D and CD16 was observed in NK cells. Overall, the findings of the study are in favor of the Sputnik V vaccine not provoking a dramatic phenotypic rearrangement in T and NK cells, although it induces their slight temporal non-specific activation.

Challenges and Recent Advancements in COVID-19 Vaccines

Vaccination is the most effective method for the prevention of COVID-19 caused by SARS-CoV-2, which is still a global epidemic. However, the evolution of SARS-CoV-2 is so rapid that various variants, including the Alpha, Beta, Gamma, Delta, and Omicron variants, have emerged, lowering the protection rate of vaccines and even resulting in breakthrough infections. Additionally, some rare but severe adverse reactions induced by COVID-19 vaccines may raise safety concerns and hinder vaccine promotion; however, clinical studies have shown that the benefits of vaccination outweigh the risks caused by adverse reactions. Current vaccines approved with emergency use authorization (EUA) were originally adaptive for adults only, and infants, children, and adolescents are not included. New-generation vaccines are needed to overcome the challenges of limited adaptive age population, breakthrough infection (mainly due to virus variant emergencies), and critical adverse reactions. Fortunately, some advances in COVID-19 vaccines have been obtained regarding enlarged adaptive populations for clinical applications, such as the Pfizer/BioNTech vaccine and the Moderna vaccine. In this article, we provide a review on the challenges and recent advancements in COVID-19 vaccines. The development of next-generation COVID-19 vaccines should lay emphasis on the expansion of adaptive age populations in all individuals, the induction of immune responses to viral variants, the avoidance or alleviation of rare but potentially critical adverse reactions, and the discovery of subunit vaccines with adjuvants encapsulated in nanoparticles.

SARS-CoV-2 Breakthrough Infections after Third Doses Boost IgG Specific Salivary and Blood Antibodies

SARS-CoV-2 breakthrough infections, associated with waning immunity, increase systemic antibody levels. In this study, we analyzed the impact of the infection timing on the magnitude of the systemic humoral response and whether breakthrough infections also boost antibody levels in the salivary compartment. We observed that the combination of infection plus vaccination, regardless of infection timing, produced a sharp increase in systemic antibodies, which were higher in subjects infected after third doses. Moreover, despite high systemic antibody levels, breakthrough infections after dose three occurred and boosted antibody levels in the salivary compartment. These results suggest that current vaccination strategies against COVID-19 should be improved. Results also showed that determination of salivary antibodies against SARS-CoV-2 could be a valuable tool in disease prevalence studies, for the follow-up of vaccinated individuals, and to assist vaccination strategies against COVID-19, especially in settings where blood sampling cannot be fulfilled.

COVID-19 Vaccines-All You Want to Know

The severe acute respiratory syndrome-coronavirus-2 (SARS-CoV-2) pandemic has led to an unprecedented public health crisis. The collective global response has led to production of multiple safe and effective vaccines utilizing novel platforms to combat the virus that have propelled the field of vaccinology forward. Significant challenges to universal vaccine effectiveness remain, including immune evasion by SARS-CoV-2 variants, waning of immune response, inadequate knowledge of correlates of protection, and dosing in special populations. This review serves as a detailed evaluation of the development of the current SARS-CoV-2 vaccines, their effectiveness, and challenges to their deployment as a preventive tool.

COVID-19 Vaccination Responses with Different Vaccine Platforms in Patients with Inborn Errors of Immunity

Patients with inborn errors of immunity (IEI) in Argentina were encouraged to receive licensed Sputnik, AstraZeneca, Sinopharm, Moderna, and Pfizer vaccines, even though most of the data of humoral and cellular responses combination on available vaccines comes from trials conducted in healthy individuals. We aimed to evaluate the safety and immunogenicity of the different vaccines in IEI patients in Argentina. The study cohort included adults and pediatric IEI patients (n = 118) and age-matched healthy controls (HC) (n = 37). B cell response was evaluated by measuring IgG anti-spike/receptor binding domain (S/RBD) and anti-nucleocapsid(N) antibodies by ELISA. Neutralization antibodies were also assessed with an alpha-S protein-expressing pseudo-virus assay. The T cell response was analyzed by IFN-γ secretion on S- or N-stimulated PBMC by ELISPOT and the frequency of S-specific circulating T follicular-helper cells (TFH) was evaluated by flow cytometry.No moderate/severe vaccine-associated adverse events were observed. Anti-S/RBD titers showed significant differences in both pediatric and adult IEI patients versus the age-matched HC cohort (p < 0.05). Neutralizing antibodies were also significantly lower in the patient cohort than in age-matched HC (p < 0.01). Positive S-specific IFN-γ response was observed in 84.5% of IEI patients and 82.1% presented S-specific TFH cells. Moderna vaccines, which were mainly administered in the pediatric population, elicited a stronger humoral response in IEI patients, both in antibody titer and neutralization capacity, but the cellular immune response was similar between vaccine platforms. No difference in humoral response was observed between vaccinated patients with and without previous SARS-CoV-2 infection.In conclusion, COVID-19 vaccines showed safety in IEI patients and, although immunogenicity was lower than HC, they showed specific anti-S/RBD IgG, neutralizing antibody titers, and T cell-dependent cellular immunity with IFN-γ secreting cells. These findings may guide the recommendation for a vaccination with all the available vaccines in IEI patients to prevent COVID-19 disease.

Omicron Variant of SARS-CoV-2: An Indian Perspective of Vaccination and Management

Omicron variants have highly influenced the entire globe. It has a high rate of transmissibility, which makes its management tedious. There are various subtypes of omicron, namely BA.1, BA.2, BA.3, BA.4, and BA.5. Currently, one omicron subvariant BF.7 is also immersed in some parts of India. Further studies are required for a better understanding of the new immersing SARS-CoV-2 subvariant of the omicron. They differ in the mutation of the spike proteins, which alters their attachment to the host receptor and hence modifies their virulence and adaptability. Delta variants have a great disastrous influence on the entire world, especially in India. While overcoming it, another mutant catches the pace. The Indian population is highly affected by omicron variants. It alters the entire management and diagnosis system against COVID-19. It demanded forcemeat in the health care system, both qualitatively and quantitively, to cope with the omicron wave. The alteration in spike protein, which is the major target of vaccines, leads to varied immunization against the subvariants. The efficacy of vaccines against the new variant was questioned. Every vaccine had a different shielding effect on the new variant. The hesitancy of vaccination was a prevalent factor in India that might have contributed to its outbreak. The prevalence of omicron, monkeypox, and tomato flu shared some similarities and distinct features when compared to their influence on the Indian population. This review emphasizes the changes omicron brings with it and how the Indian health care system outrage this dangerous variant.

Assessing the long-stand antibody response induced by COVID-19 vaccines: A study in an educational cohort in San Luis, Argentina

BACKGROUND

Although there has developed an increased interest in the vaccines BNT1622b2 (Pfizer/BioNTech), mRNA-1273 (Moderna/NIAID), and ChAdOx1 nCoV-19 (AstraZeneca/University of Oxford), there are still few reports describing the immune response induced by different vaccine platforms in real-world settings of low-income countries. Here, we proposed to analyse the humoral immune response elicited by the primary vaccines used in Argentina from July-December 2021.

METHODS

Anti-SARS-CoV-2-Spike-RBD IgG and neutralising antibodies were assayed by ELISA in a total of 871 serum samples obtained from 376 volunteers from an educational staff. The individuals were vaccinated with BBIBP-CorV (Sinopharm), ChAdOx1 nCoV-19 (AstraZeneca/University of Oxford, AZ), Gam-COVID-Vac (Sputnik V, SpV) or combined vaccines (mostly SpV and mRNA-1273, Moderna). The antibody response was analysed several days after the initial vaccination (20, 40, 120 and 180 days).

RESULTS

After receiving at least one dose of the COVID-19 vaccine, we detected 93.34% of seroprevalence. Previously SARS-CoV-2 infected showed higher antibody concentrations compared with naïve vaccinees. Six months after the initial vaccination, combined vaccination induced higher anti-SARS-CoV-2 antibody levels than the other vaccines in naïve volunteers. However, we did not find differences in the neutralising responses after any vaccine from naïve vaccines or between the naïve and previously infected volunteers on day 120 after vaccination.

CONCLUSIONS

Our long-term analysis of volunteers from the educational system provides data in a real-world context, showing the benefits of a boost dose still in previously infected volunteers, and suggesting the advantages of a heterologous prime-boost schedule.

Distinct Immune Phenotypes and Cytokine Profiles in Children with Differing Severity of COVID-19

BACKGROUND

Coronavirus disease 2019 (COVID-19) is usually mild and self-limited in children. However, a few Severe acute respiratory syndrome coronavirus 2 (SARS-CoV2) infections in children may progress to severe disease with respiratory distress or can result in a multisystem inflammatory syndrome (MIS-C) associated with COVID-19. The immune mechanisms for these differential clinical outcomes are largely unknown.

METHODS

A prospective cohort study was performed to analyze the laboratory parameters, antibody response, immune phenotypes and cytokine profiles of 51 children with different clinical presentations of COVID-19.

RESULTS

We found that the absolute lymphocyte counts gradually decreased with disease severity. Furthermore, SARS-CoV-2 IgG levels in the acute phase and convalescence were not significantly different in patients with different disease severity. A decrease in CD3 + , CD4 + and CD8 + T cells was observed as disease severity increased. Both CD4 + and CD8 + T cells were activated in children with COVID-19, but no difference in the percentage of HLADR + -expressing cells was detected across the severity groups. In contrast, MIS-C patients exhibited augmented exhausted effector memory CD8 + T cells. Interestingly, the cytokine profile in sera of moderate/severe and MIS-C patients revealed an increase in anti-inflammatory IL-1RA and a suppression of tumor necrosis factor-α, RANTES, eotaxin and PDGF-BB. MIS-C patients also exhibited augmented IL-1β.

CONCLUSIONS

We report distinct immune profiles dependent on severity in pediatric COVID-19 patients. Further investigation in a larger population will help unravel the immune mechanisms underlying pediatric COVID-19.

Analysis and comparison of anti-RBD neutralizing antibodies from AZD-1222, Sputnik V, Sinopharm and Covaxin vaccines and its relationship with gender among health care workers

Background

Vaccine efficiency has a significant role in the public perception of vaccination. The current study was designed to evaluate the efficacy of COVID-19 vaccines (AZD-1222, Sputnik-V, Sinopharm, and Covaxin) and the effect of gender on vaccine efficacy. We evaluated the efficacy of these vaccines among 214 health care employees in Iran. Blood samples were taken from all participants on day 0 and 14 days after the second dose. Humoral responses were evaluated by the PT-SARS-CoV-2-Neutralizing-Ab-96.

Results

The frequency of immunized individuals in the Sputnik V and AZD-1222 groups was 91% and 86%, respectively. This rate was 61% and 67% for Sinopharm and Covaxin vaccines. A comparison of the results obtained from the effectiveness of the vaccines between female and male groups did not demonstrate a significant difference.

Conclusion

According to the results, Sputnik V and AZD-1222 vaccines were more effective than Sinopharm and Covaxin vaccines. Moreover, the effectiveness of these vaccines is not related to gender.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12979-022-00303-x.

Variants of Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) and Vaccine Effectiveness

The incidence and death toll due to SARS-CoV-2 infection varied time-to-time; and depended on several factors, including severity (viral load), immune status, age, gender, vaccination status, and presence of comorbidities. The RNA genome of SARS-CoV-2 has mutated and produced several variants, which were classified by the SARS-CoV-2 Interagency Group (SIG) into four major categories. The first category; “Variant Being Monitored (VBM)”, consists of Alpha (B.1.1.7), Beta (B.1.351), Gamma (P.1), Delta (B.1.617.2), Epsilon (B.1.427, B.1.429), Eta (B.1.525), Iota (B.1.526), Kappa (B.1.617.1), Mu (B.1.621), and Zeta (P.2); the second category; “Variants of Concern” consists of Omicron (B.1.1.529). The third and fourth categories include “Variants of Interest (VOI)”, and “Variants of High Consequence (VOHC)”, respectively, and contain no variants classified currently under these categories. The surge in VBM and VOC poses a significant threat to public health globally as they exhibit altered virulence, transmissibility, diagnostic or therapeutic escape, and the ability to evade the host immune response. Studies have shown that certain mutations increase the infectivity and pathogenicity of the virus as demonstrated in the case of SARS-CoV-2, the Omicron variant. It is reported that the Omicron variant has >60 mutations with at least 30 mutations in the Spike protein (“S” protein) and 15 mutations in the receptor-binding domain (RBD), resulting in rapid attachment to target cells and immune evasion. The spread of VBM and VOCs has affected the actual protective efficacy of the first-generation vaccines (ChAdOx1, Ad26.COV2.S, NVX-CoV2373, BNT162b2). Currently, the data on the effectiveness of existing vaccines against newer variants of SARS-CoV-2 are very scanty; hence additional studies are immediately warranted. To this end, recent studies have initiated investigations to elucidate the structural features of crucial proteins of SARS-CoV-2 variants and their involvement in pathogenesis. In addition, intense research is in progress to develop better preventive and therapeutic strategies to halt the spread of COVID-19 caused by variants. This review summarizes the structure and life cycle of SARS-CoV-2, provides background information on several variants of SARS-CoV-2 and mutations associated with these variants, and reviews recent studies on the safety and efficacy of major vaccines/vaccine candidates approved against SARS-CoV-2, and its variants.

Humoral response and neutralising capacity at 6 months post-vaccination against COVID-19 among institutionalised older adults in Argentina

The COVID-19 pandemic has particularly affected older adults residing in nursing homes, resulting in high rates of hospitalisation and death. Here, we evaluated the longitudinal humoral response and neutralising capacity in plasma samples of volunteers vaccinated with different platforms (Sputnik V, BBIBP-CorV, and AZD1222). A cohort of 851 participants, mean age 83 (60-103 years), from the province of Buenos Aires, Argentina were included. Sequential plasma samples were taken at different time points after vaccination. After completing the vaccination schedule, infection-naïve volunteers who received either Sputnik V or AZD1222 exhibited significantly higher specific anti-Spike IgG titers than those who received BBIBP-CorV. Strong correlation between anti-Spike IgG titers and neutralising activity levels was evidenced at all times studied (rho=0.7 a 0.9). Previous exposure to SARS-CoV-2 and age <80 years were both associated with higher specific antibody levels. No differences in neutralising capacity were observed for the infection-naïve participants in either gender or age group. Similar to anti-Spike IgG titers, neutralising capacity decreased 3 to 9-fold at 6 months after initial vaccination for all platforms. Neutralising capacity against Omicron was between 10-58 fold lower compared to ancestral B.1 for all vaccine platforms at 21 days post dose 2 and 180 days post dose 1. This work provides evidence about the humoral response and neutralising capacity elicited by vaccination of a vulnerable elderly population. This data could be useful for pandemic management in defining public health policies, highlighting the need to apply reinforcements after a complete vaccination schedule.

Humoral immunoresponse elicited against an adenoviral-based SARS-CoV-2 coronavirus vaccine in elderly patients

The early sequencing of the SARS-CoV-2 viral genome allowed for a speedy development of effective vaccines against the virus. Nevertheless, age-related immunosenescence, the inability to mount strong immune responses, still represents a major obstacle. Here, in a group of 149 elderly volunteers (70-96 years old), evolution of the humoral immune response over time to Gam-COVID-Vac (Sputnik V), a vaccine based on heterologous recombinant adenovirus-26 (Ad26) and adenovirus-5 (Ad5) carrying the Spike genome, was analyzed by an anti-RBD ELISA. At 28 days post vaccination (dpv), a seroconversion rate of 91% was achieved, showing the importance of administering at least two doses of Gam-COVID-Vac to elicit a robust immune response, especially in elderly individuals without previous SARS-CoV-2 infection. Interestingly, IgG specific antibodies that reached their highest titers around 28 dpv (median = 740), persisted without significant decrease after 60 dpv (median = 650). After 90 dpv, IgG titers began to drop, and at 180 dpv only 44.7% of the elderly individuals remained with detectable anti-RBD IgG antibodies. No significant differences were observed in specific humoral immune responses between genders at early times point. However, at 60 dpv anti-RBD titers were more persistent in elderly females, and only dropped at 90 dpv (p < 0.0001). As expected, the highest antibodies titers were elicited in the youngest subgroup (70-74 years). Our results show that Gam-COVID-Vac was able to deal with the ageing of the immune system, eliciting a robust immune response in an elderly cohort, which lasted approximately 90 dpv at high levels, and protected against COVID-19.

Viral vector and nucleic acid vaccines against COVID-19: A narrative review

After about 2 years since the first detection of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infections in Wuhan, China, in December 2019 that resulted in a worldwide pandemic, 6.2 million deaths have been recorded. As a result, there is an urgent need for the development of a safe and effective vaccine for coronavirus disease 2019 (COVID-19). Endeavors for the production of effective vaccines inexhaustibly are continuing. At present according to the World Health Organization (WHO) COVID-19 vaccine tracker and landscape, 153 vaccine candidates are developing in the clinical phase all over the world. Some new and exciting platforms are nucleic acid-based vaccines such as Pfizer Biontech and Moderna vaccines consisting of a messenger RNA (mRNA) encoding a viral spike protein in host cells. Another novel vaccine platform is viral vector vaccine candidates that could be replicating or nonreplicating. These types of vaccines that have a harmless viral vector like adenovirus contain a genome encoding the spike protein of SARS-CoV-2, which induces significant immune responses. This technology of vaccine manufacturing has previously been used in many human clinical trials conducted for adenoviral vector-based vaccines against different infectious agents, including Ebola virus, Zika virus, HIV, and malaria. In this paper, we have a review of nucleic acid-based vaccines that are passing their phase 3 and 4 clinical trials and discuss their efficiency and adverse effects.

Assessment of the humoral immunity induced by Sputnik V Covid-19 vaccine (GAM-COVID-VAC) in healthcare workers

Background

Vaccination for COVID-19 in healthcare workers (HCW) is essential to protect one of the populations most exposed to this disease. However, data on the humoral response rate to the vaccine and the factors associated with it in this population are limited. Therefore, we aimed to evaluate the antibody response against SARS-CoV-2 in HCWs with complete Sputnik V vaccine scheme and factors associated with an increased antibody response.

Material and methods

Prospective study to evaluate the anti-SARS-CoV-2 humoral response in HCWs vaccinated with two doses of the Sputnik V vaccine (April-July 2021). The assessment of anti-Spike IgG antibodies in plasma was performed using the COVIDAR IgG enzyme-linked immunosorbent assay. A logistic regression was performed to identify independent factors associated with a positive IgG serology test and an elevated antibody response.

Results

A total of 630 HCWs were enrolled. Median age (IQR): 47 years (35-56). Female sex: 462 (73.33%). Previous COVID-19: 158 (25%). The median interval time between vaccine doses was 3 (3-4) weeks. Positive serology was observed in 607 (96.35%) HCWs. In the multivariate analysis, a history of systemic reactogenicity was identified as an independent variable associated with a positive serology; and history of systemic reactogenicity, COVID-19, interval between doses ≥ 4 weeks and time to serology < 14 weeks were associated with an elevated antibody response.

Conclusions

This study provides data on the humoral response to the Sputnik V vaccine in a real-life setting. These initial data can contribute to the development of future immunization strategies in HCWs.

Long-term antibody response following SPUTNIK V primary vaccination in healthcare workers with and without history of SARS-CoV-2 infection: Prospective cohort study from a hospital in Argentina

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After completing a two-dose Sputnik V schedule, all vaccinees developed antibodies.

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Prior infection was associated with higher antibody concentrations.

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Antibodies decreased significantly after 6 months in naïve subjects.

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In subjects without infection, 17% were negative at day 180.

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SARS-CoV2 infection after vaccination increased antibody concentrations.

Background

In December 2020, Sputnik V was incorporated to the National COVID-19 Immunization Plan in Argentina. Studies had shown 98% of antibody response rate. To date, data on immunogenicity and antibody persistence in Argentina are scarce.

The objective was to assess humoral immune response after two doses of Sputnik V in Health Care Workers (HCWs) at the Ricardo Gutierrez Children’s Hospital (RGCH).

Methods

A prospective, cohort study in HCWs immunized with two doses of Sputnik V between February and March 2021. The following variables were assessed: age, gender, risk factors for severe COVID-19 or mortality, immunosuppressive therapy and history of SARS-CoV-2. Blood samples were drawn on the day of the first dose, 28 days and 180 days after the second. Anti-Spike IgG was measured using an ELISA assay. Differences in immune response were evaluated according to study variables. Comparison analyses between groups with or without history of infection were performed, with T-test and ANOVA or Mann-Whitney tests. For each subject, we compared baseline values with 28 days and 180 days after the second vaccine.

STATA version 14 and R Sofware were used for data analyses.

Results

We included 528 individuals, mean age 41.5 years, 82.9% female, 14.4% (76/528) reported previous SARS-CoV-2 infection.

All subjects developed antibodies post-vaccination. At day 28, concentrations were significantly higher in previously infected than naïve subjects (p < 0.001) with no differences according to age, gender and comorbidities.

At day 180, 17% (95% CI 13.17–21.53) of naïve subjects were negative. Antibody concentrations decreased significantly in all subjects except in those who reported SARS-CoV-2 infection after vaccination (n = 31). This last group had significantly higher antibody concentrations.

Conclusion

This study assessed immune response to a new COVID-19 vaccine in real life in a cohort of subjects. Antibody concentrations varied according to history of SARS-COV-2 infection and decreased over time.

Sputnik-V reactogenicity and immunogenicity in the blood and mucosa: a prospective cohort study

Sputnik-V (Gam-COVID-Vac) is a heterologous, recombinant adenoviral (rAdv) vector-based, COVID-19 vaccine now used in > 70 countries. Yet there is a shortage of data on this vaccine's performance in diverse populations. Here, we performed a prospective cohort study to assess the reactogenicity and immunologic outcomes of Sputnik-V vaccination in Kazakhstan. COVID-19-free participants (n = 82 at baseline) were followed at day 21 after Sputnik-V dose 1 (rAd5) and dose 2 (rAd26). Self-reported local and systemic adverse events were captured using questionnaires. Blood and nasopharyngeal swabs were collected to perform SARS-CoV-2 diagnostic and immunologic assays. We observed that most of the reported adverse events were mild-to-moderate injection site or systemic reactions, no severe or potentially life-threatening conditions were reported, and dose 1 appeared to be more reactogenic than dose 2. The seroconversion rate was 97% post-dose 1, remaining the same post-dose 2. The proportion of participants with detectable virus neutralization was 83% post-dose 1, increasing to 98% post-dose 2, with the largest relative increase observed in participants without prior COVID-19 exposure. Dose 1 boosted nasal S-IgG and S-IgA, while the boosting effect of dose 2 on mucosal S-IgG, but not S-IgA, was only observed in subjects without prior COVID-19. Systemically, vaccination reduced serum levels of growth regulated oncogene (GRO), which correlated with an elevation in blood platelet count. Overall, Sputnik-V dose 1 elicited both blood and mucosal SARS-CoV-2 immunity, while the immune boosting effect of dose 2 was minimal. Thus, adjustments to the current vaccine dosing regimen are necessary to optimize immunization efficacy and cost-effectiveness. While Sputnik-V reactogenicity is similar to that of other COVID-19 vaccines, the induced alterations to the GRO/platelet axis warrant investigation of the vaccine’s effects on systemic immunology.

High SARS-CoV-2 seroprevalence in Karaganda, Kazakhstan before the launch of COVID-19 vaccination

COVID-19 exposure in Central Asia appears underestimated and SARS-CoV-2 seroprevalence data are urgently needed to inform ongoing vaccination efforts and other strategies to mitigate the regional pandemic. Here, in a pilot serologic study we assessed the prevalence of SARS-CoV-2 antibody-mediated immunity in a multi-ethnic cohort of public university employees in Karaganda, Kazakhstan. Asymptomatic subjects (n = 100) were recruited prior to their first COVID-19 vaccination. Questionnaires were administered to capture a range of demographic and clinical characteristics. Nasopharyngeal swabs were collected for SARS-CoV-2 RT-qPCR testing. Serological assays were performed to detect spike (S)-reactive IgG and IgA and to assess virus neutralization. Pre-pandemic samples were used to validate the assay positivity thresholds. S-IgG and -IgA seropositivity rates among SARS-CoV-2 PCR-negative participants (n = 100) were 42% (95% CI [32.2-52.3]) and 59% (95% CI [48.8-69.0]), respectively, and 64% (95% CI [53.4-73.1]) of the cohort tested positive for at least one of the antibodies. S-IgG titres correlated with virus neutralization activity, detectable in 49% of the tested subset with prior COVID-19 history. Serologically confirmed history of COVID-19 was associated with Kazakh ethnicity, but not with other ethnic minorities present in the cohort, and self-reported history of respiratory illness since March 2020. Overall, SARS-CoV-2 exposure in this cohort was ~15-fold higher compared to the reported all-time national and regional COVID-19 prevalence, consistent with recent studies of excess infection and death in Kazakhstan. Continuous serological surveillance provides important insights into COVID-19 transmission dynamics and may be used to better inform the regional public health response.

Safety and Efficacy of Combined Intramuscular/Intranasal RAZI-COV PARS Vaccine Candidate Against SARS-CoV-2: A Preclinical Study in Several Animal Models

Several vaccine candidates for COVID-19 have been developed, and few vaccines received emergency approval with an acceptable level of efficacy and safety. We herein report the development of the first recombinant protein-based vaccine in Iran based on the recombinant SARS-CoV-2 spike protein in its monomeric (encompassing amino acid 1-674 for S1 and 685-1211 for S2 subunits) and trimer form (S-Trimer) formulated in the oil-in-water adjuvant system RAS-01 (Razi Adjuvant System-01). The safety and immunity of the candidate vaccine, referred to as RAZI-COV PARS, were evaluated in Syrian hamster, BALB/c mice, Pirbright guinea pig, and New Zeeland white (NZW) rabbit. All vaccinated animals received two intramuscular (IM) and one intranasal (IN) candidate vaccine at 3-week intervals (days 0, 21, and 51). The challenge study was performed intranasally with 5×106 pfu of SARS-CoV-2 35 days post-vaccination. None of the vaccinated mice, hamsters, guinea pigs, or rabbits showed any changes in general clinical observations; body weight and food intake, clinical indicators, hematology examination, blood chemistry, and pathological examination of vital organs. Safety of vaccine after the administration of single and repeated dose was also established. Three different doses of candidate vaccine stimulated remarkable titers of neutralizing antibodies, S1, Receptor-Binding Domain (RBD), and N-terminal domain (NTD) specific IgG antibodies as well as IgA antibodies compared to placebo and control groups (P<0.01). Middle and high doses of RAZI-COV PARS vaccine significantly induced a robust and quick immune response from the third-week post-immunization. Histopathological studies on vaccinated hamsters showed that the challenge with SARS-CoV-2 did not induce any modifications in the lungs. The protection of the hamster was documented by the absence of lung pathology, the decreased virus load in the lung, rapid clearance of the virus from the lung, and strong humoral and cellular immune response. These findings confirm the immunogenicity and efficacy of the RAZI-COV PARS vaccine. Of the three tested vaccine regimens, the middle dose of the vaccine showed the best protective immune parameters. This vaccine with heterologous prime-boost vaccination method can be a good candidate to control the viral infection and its spread by stimulating central and mucosal immunity.

An overview of current drugs and prophylactic vaccines for coronavirus disease 2019 (COVID-19)

Designing and producing an effective vaccine is the best possible way to reduce the burden and spread of a disease. During the coronavirus disease 2019 (COVID-19) pandemic, many large pharmaceutical and biotechnology companies invested a great deal of time and money in trying to control and combat the disease. In this regard, due to the urgent need, many vaccines are now available earlier than scheduled. Based on their manufacturing technology, the vaccines available for COVID-19 (severe acute respiratory syndrome coronavirus 2 (SAR-CoV2)) infection can be classified into four platforms: RNA vaccines, adenovirus vector vaccines, subunit (protein-based) vaccines, and inactivated virus vaccines. Moreover, various drugs have been deemed to negatively affect the progression of the infection via various actions. However, adaptive variants of the SARS-CoV-2 genome can alter the pathogenic potential of the virus and increase the difficulty of both drug and vaccine development. In this review, along with drugs used in COVID-19 treatment, currently authorized COVID-19 vaccines as well as variants of the virus are described and evaluated, considering all platforms.

BNT162b2, mRNA-1273, and Sputnik V Vaccines Induce Comparable Immune Responses on a Par With Severe Course of COVID-19

Vaccines against the severe acute respiratory syndrome coronavirus 2, which have been in urgent need and development since the beginning of 2020, are aimed to induce a prominent immune system response capable of recognizing and fighting future infection. Here we analyzed the levels of IgG antibodies against the receptor-binding domain (RBD) of the viral spike protein after the administration of three types of popular vaccines, BNT162b2, mRNA-1273, or Sputnik V, using the same ELISA assay to compare their effects. An efficient immune response was observed in the majority of cases. The obtained ranges of signal values were wide, presumably reflecting specific features of the immune system of individuals. At the same time, these ranges were comparable among the three studied vaccines. The anti-RBD IgG levels after vaccination were also similar to those in the patients with moderate/severe course of the COVID-19, and significantly higher than in the individuals with asymptomatic or light symptomatic courses of the disease. No significant correlation was observed between the levels of anti-RBD IgG and sex or age of the vaccinated individuals. The signals measured at different time points for several individuals after full Sputnik V vaccination did not have a significant tendency to lower within many weeks. The rate of neutralization of the interaction of the RBD with the ACE2 receptor after vaccination with Sputnik V was on average slightly higher than in patients with a moderate/severe course of COVID-19. The importance of the second dose administration of the two-dose Sputnik V vaccine was confirmed: while several individuals had not developed detectable levels of the anti-RBD IgG antibodies after the first dose of Sputnik V, after the second dose the antibody signal became positive for all tested individuals and raised on average 5.4 fold. Finally, we showed that people previously infected with SARS-CoV-2 developed high levels of antibodies, efficiently neutralizing interaction of RBD with ACE2 after the first dose of Sputnik V, with almost no change after the second dose.

[Assessment of the humoral immunity induced by Sputnik V COVID-19 vaccine (Gam-COVID-Vac) in healthcare workers]

Introducción

La vacunación para la COVID-19 en el personal de salud (PDS) es fundamental para proteger a una de las poblaciones más expuestas a esta enfermedad. Sin embargo, los datos de la tasa de respuesta humoral a la vacuna y los factores asociados a la misma en esta población son limitados. Nuestros objetivos fueron evaluar la respuesta de los anticuerpos contra SARS-CoV-2 en el PDS con el esquema completo de la vacuna Sputnik V y los factores asociados con una mayor respuesta de los anticuerpos.

Materiales y métodos

Estudio prospectivo de evaluación de la respuesta humoral anti-SARS-CoV-2 en el PDS con el esquema completo de la vacuna Sputnik V mediante el enzimoinmunoanálisis COVIDAR IgG (abril–julio 2021). Se realizó una regresión logística para identificar los factores independientes asociados con una prueba de serología IgG positiva y con una respuesta elevada de anticuerpos.

Resultados

Se enrolaron 630 PDS. Mediana (RIC) de edad: 47 años (35-56). Sexo femenino: 462 (73,33%). COVID previo: 158 (25%). Mediana de tiempo entre las dosis de vacuna fue de 3 (3-4) semanas. Presentaron serología reactiva 607 (96,35%). En el análisis multivariado se identificó como variable independiente asociada a la serología positiva al antecedente de reactogenicidad sistémica a la vacuna; y con una respuesta elevada de los anticuerpos al antecedente de reactogenicidad sistémica a la vacuna, COVID-19 previo, intervalo entre dosis ≥ 4 semanas y tiempo a serología < 14 semanas.

Conclusiones

Este estudio proporciona datos de la respuesta humoral a la vacuna Sputnik V en un escenario de la vida real. Estos datos iniciales pueden contribuir al desarrollo de futuras estrategias de inmunización en el PDS.

Memory B Cells Induced by Sputnik V Vaccination Produce SARS-CoV-2 Neutralizing Antibodies Upon Ex Vivo Restimulation

The development of effective vaccines against SARS-CoV-2 remains a global health priority. Despite extensive use, the effects of Sputnik V on B cell immunity need to be explored in detail. We performed comprehensive profiling of humoral and B cell responses in a cohort of vaccinated subjects (n = 22), and demonstrate that Sputnik vaccination results in robust B cell immunity.

We show that B memory cell (MBC) and antibody responses to Sputnik V were heavily dependent on whether the vaccinee had a history of SARS-CoV-2 infection or not. 85 days after the first dose of the vaccine, ex vivo stimulated MBCs from the vast majority of Sputnik V vaccinees produced antibodies that robustly neutralized the Wuhan Spike-pseudotyped lentivirus. MBC-derived antibodies from all previously infected and some of the naïve vaccine recipients could also cross-neutralize Beta (B.1.351) variant of SARS-CoV-2.

Virus-neutralizing activity of MBC-derived antibodies correlated well with that of the serum antibodies, suggesting the interplay between the MBC and long-lived plasma cell responses. Thus, our in-depth analysis of MBC responses in Sputnik V vaccinees complements traditional serological approaches and may provide important outlook into future B cell responses upon re-encounter with the emerging variants of SARS-CoV-2.

Boosting of the SARS-CoV-2-Specific Immune Response after Vaccination with Single-Dose Sputnik Light Vaccine

Despite measures taken world-wide, the coronavirus disease 2019 (COVID-19) pandemic continues. Because efficient antiviral drugs are not yet widely available, vaccination is the best option to control the infection rate. Although this option is obvious in the case of COVID-19-naive individuals, it is still unclear when individuals who have recovered from a previous SARS-CoV-2 infection should be vaccinated and whether the vaccination raises immune responses against the coronavirus and its novel variants. In this study, we collected peripheral blood from 84 healthy human donors of different COVID-19 status who were vaccinated with the Sputnik Light vaccine and measured the dynamics of the Ab and T cell responses, as well as the virus-neutralizing activity (VNA) in serum, against two SARS-CoV-2 variants, B.1.1.1 and B.1.617.2. We showed that vaccination of individuals previously exposed to the virus considerably boosts the existing immune response. In these individuals, receptor-binding domain (RBD)-specific IgG titers and VNA in serum were already elevated on the 7th day after vaccination, whereas COVID-19-naive individuals developed the Ab response and VNA mainly 21 d postvaccination. Additionally, we found a strong correlation between RBD-specific IgG titers and VNA in serum, and according to these data vaccination may be recommended when the RBD-specific IgG titers drop to 142.7 binding Ab units/ml or below. In summary, the results of the study demonstrate that vaccination is beneficial for both COVID-19-naive and recovered individuals, especially since it raises serum VNA against the B.1.617.2 variant, one of the five SARS-CoV-2 variants of concern.

Longitudinal Study after Sputnik V Vaccination Shows Durable SARS-CoV-2 Neutralizing Antibodies and Reduced Viral Variant Escape to Neutralization over Time

Recent studies have shown a temporal increase in the neutralizing antibody potency and breadth to SARS-CoV-2 variants in coronavirus disease 2019 (COVID-19) convalescent individuals. Here, we examined longitudinal antibody responses and viral neutralizing capacity to the B.1 lineage virus (Wuhan related), to variants of concern (VOC; Alpha, Beta, Gamma, and Delta), and to a local variant of interest (VOI; Lambda) in volunteers receiving the Sputnik V vaccine in Argentina. Longitudinal serum samples (N = 536) collected from 118 volunteers obtained between January and October 2021 were used. The analysis indicates that while anti-spike IgG levels significantly wane over time, the neutralizing capacity for the Wuhan-related lineages of SARS-CoV-2 and VOC is maintained within 6 months of vaccination. In addition, an improved antibody cross-neutralizing ability for circulating variants of concern (Beta and Gamma) was observed over time postvaccination. The viral variants that displayed higher escape to neutralizing antibodies with respect to the original virus (Beta and Gamma variants) were the ones showing the largest increase in susceptibility to neutralization over time after vaccination. Our observations indicate that serum neutralizing antibodies are maintained for at least 6 months and show a reduction of VOC escape to neutralizing antibodies over time after vaccination. IMPORTANCE Vaccines have been produced in record time for SARS-CoV-2, offering the possibility of halting the global pandemic. However, inequalities in vaccine accessibility in different regions of the world create a need to increase international cooperation. Sputnik V is a recombinant adenovirus-based vaccine that has been widely used in Argentina and other developing countries, but limited information is available about its elicited immune responses. Here, we examined longitudinal antibody levels and viral neutralizing capacity elicited by Sputnik V vaccination. Using a cohort of 118 volunteers, we found that while anti-spike antibodies wane over time, the neutralizing capacity to viral variants of concern and local variants of interest is maintained within 4 months of vaccination. In addition, we observed an increased cross-neutralization activity over time for the Beta and Gamma variants. This study provides valuable information about the immune response generated by a vaccine platform used in many parts of the world.

Seroprevalence of SARS-CoV-2 antibodies among primary healthcare workers in the Republic of Srpska, Bosnia & Herzegovina: A cross-sectional study

Healthcare workers (HCW) in primary healthcare centres in the Republic of Srpska, Bosnia and Herzegovina, are on the first combat line with COVID-19. This study aimed to assess the seroprevalence of SARS-CoV-2 among HCW at the primary healthcare centres and to analyse the risk exposure to COVID-19, clinical signs and vaccination status. A cross-sectional study was conducted among HCW at the selected primary healthcare centres between 19 March and 30 April 2021. Antibodies against the SARS-CoV-2 virus were detected by enzyme-linked immunosorbent assay (ELISA). A total of 1,023 HCW (mean age 45 years; 71% female) were included in the study. The anti-SARS-CoV-2 antibodies were detected in 69.5% of all participants. There was a significant difference in seropositivity among primary healthcare centres from different geographical regions. As many as 432 (42%) of all participants had confirmed COVID-19 symptoms before the study and, 84.8% of them were seropositive. This study showed that 702 primary HCW were vaccinated with any of these vaccines: Sputnik V, Sinopharm, Pfizer/Biontech. High titre of SARS-CoV-2 antibodies was found amongst those who received one (92.6%) or both (97.2%) doses of vaccines. In this study, we report high prevalence of SARS-CoV-2 antibody among HCW in primary healthcare in the Republic of Srpska, Bosnia and Herzegovina during the third pandemic wave.

Evaluation of the Gam-COVID-Vac and vaccine-induced neutralizing response against SARS-CoV-2 lineage P.1 variant in an Argentinean cohort

We evaluated humoral immune-response elicited by Sputnik-V by measuring anti-Spike (S) IgG antibodies (Abs) and neutralizing antibodies (NAb) prior to, 14 and 42 days after-vaccination. The safety and disease rates among vaccinated individuals were also evaluated. Since SARS-CoV-2 lineage P.1 is rapidly spreading in Argentina, virus-neutralizing activity of Sputnik-V-elicited and infection-elicited NAb faced to P.1 were also assessed. A total of 285 participants were recruited; all reported good tolerance, without any severe adverse event. Nine COVID-19 cases were confirmed in fully vaccinated individuals and viable P.1 variant was successfully isolated from one of them. At day 42, 99.65% of the individuals had anti-S IgG; however, 23.15% had not detectable NAbs. Significantly higher neutralization potency against WT compared to P.1 (p < 0·001) was observed. Some samples failed to neutralize P.1, mainly among vaccinated-naїve subjects; however, no significant differences were observed among previously infected-vaccinated individuals. Our results corroborated that Sputnik-V is safe and induces an efficient humoral immune response, although not all immunized subjects develop Nabs. Herein, we show for the first time, evidence of infectious SARS-CoV-2 shedding from Sputnik-V fully vaccinated individuals, by the isolation of viable virus from the nasopharyngeal swab of one participant of our study, 139 days after receiving the second dose. Thereby, we provide evidence indicating that the vaccine might avoid severe forms of COVID-19 but does not prevent infection nor prevents transmission from a fully vaccinated individual.

Immune Maturation Effects on Viral Neutralization and Avidity of Hyperimmunized Equine Anti-SARS-CoV-2 Sera

Mass-vaccination against COVID-19 is still a distant goal for most low-to-middle income countries. The experience gained through decades producing polyclonal immunotherapeutics (such as antivenoms) in many of those countries is being redirected to develop similar products able to neutralize SARS-CoV-2 infection. In this study we analyzed the biological activity (viral neutralization or NtAb) and immunochemical properties of hyperimmune horses' sera (HHS) obtained during initial immunization (I) and posterior re-immunization (R) cycles using the RBD domain of the SARS-CoV-2 spike protein as antigen. HHS at the end of the R cycle showed higher NtAb titers when compared to those after the I cycle (35,585 vs. 7000 mean NtAb, respectively). Moreover, this increase paralleled an increase in avidity (95.2% to 65.2% mean avidity units, respectively). The results presented herein are relevant for manufacturers of these therapeutic tools against COVID-19.

An open, non-randomised, phase 1/2 trial on the safety, tolerability, and immunogenicity of single-dose vaccine "Sputnik Light" for prevention of coronavirus infection in healthy adults

BACKGROUND

While the world is experiencing another wave of COVID-19 pandemic, global vaccination program is hampered by an evident shortage in the supply of licensed vaccines. In an effort to satisfy vaccine demands we developed a new single-dose vaccine based on recombinant adenovirus type 26 (rAd26) vector carrying the gene for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) spike (S) glycoprotein - "Sputnik Light".

METHODS

We conducted an open label, prospective, non-randomised phase 1/2 trial aimed to assess safety, tolerability, and immunogenicity of "Sputnik Light" vaccine in a single center in Russia. Primary outcome measures were antigen-specific humoral immunity (Anti-RBD-SARS-CoV-2 antibodies measured by ELISA on days 1, 10, 28, and 42) and safety (number of participants with adverse events monitored throughout the study). Secondary outcome measures were antigen-specific cellular immunity (measured by antigen-dependent CD4+ and CD8+ T-cell proliferation, number of antigen-specific interferon-γ-producing cells as well as interferon-γ concentration upon antigen restimulation) and change in neutralizing antibodies (measured in SARS-CoV-2 neutralization assay).

FINDINGS

Most of the solicited adverse reactions were mild (66·4% from all vaccinees), few were moderate (5·5%). No serious adverse events were detected. Assessment of Anti-RBD-SARS-CoV-2 antibodies revealed a group with pre-existing immunity to SARS-CoV-2. Upon this finding we separated all safety and immunogenicity data based on pre-existing immunity to SARS-CoV-2. There were notable differences in the vaccine effects on immunogenicity by the groups. Vaccination of seropositive (N=14) volunteers rapidly boosted RBD-specific IgGs from reciprocal geometric mean titer (​GMT) 594·4 at a baseline up to 26899 comparing to 29·09 in seronegative group (N=96) by day 10. By day 42 seroconversion rate reached 100% (93/93) in seronegative group with GMT 1648. At the same time, in the seropositive group, seroconversion rate by day 42 was 92·9% (13/14) with GMT 19986. Analysis of neutralizing antibodies to SARS-CoV-2 showed 81·7% (76/93) and 92·9% (13/14) seroconversion rates by day 42 with median reciprocal GMT 15·18 and 579·7 in the seronegative and seropositive groups, respectively. Antigen-specific T cell proliferation, formation of IFNy-producing cells, and IFNy secretion were observed in 96·7% (26/27), 96% (24/25), and 96% (24/25) of the seronegative group respectively and in 100% (3/3), 100% (5/5), and 100% (5/5) of the seropositive vaccinees, respectively.

INTERPRETATION

The single-dose rAd26 vector-based COVID-19 vaccine "Sputnik Light" has a good safety profile and induces a strong humoral and cellular immune responses both in seronegative and seropositive participants.

FUNDING

Russian Direct Investment Fund.

Long-term analysis of antibodies elicited by SPUTNIK V: A prospective cohort study in Tucumán, Argentina

BACKGROUND

Gam-COVID-Vac (SPUTNIK V) has been granted emergency use authorization in 70 nations and has been administered to millions worldwide. However, there are very few peer-reviewed studies describing its effects. Independent reports regarding safety and effectiveness could accelerate the final approval by the WHO. We aimed to study the long-term humoral immune response in naïve and previously infected volunteers who received SPUTNIK V.

METHODS

Humoral immune responses, assayed by anti-SARS-CoV-2-spike-RBD IgG ELISA and neutralization assays, were measured in 602 healthcare workers at 0, 14, 28, 60 and 180 days after receiving SPUTNIK V between December 2020 and July 2021 in Tucumán, Argentina.

FINDINGS

Seroconversion was detected in 97% of individuals after 28 days post-vaccination (dpv) (N = 405). Anti-RBD titers began to decrease after 60 dpv (N = 328), but remained detectable in 94% at 90 dpv (N = 224). At 180 dpv, anti-RDB titers persisted in 31% (N = 146). Previous infection triggered an increased immune response to the first dose and increased neutralization activity against variants of concern (VOC). Second doses in previously infected individuals further increased titers, even 90 dpv (N = 75). Basal antibody titers had more influence on post-vaccination anti-RBD responses than the time elapsed between diagnosis and vaccination (N = 274).

INTERPRETATION

Data presented herein provides essential knowledge regarding the kinetics of antibodies induced by SPUTNIK V up to six months after immunization, and suggests that when considering one-dose vaccination policies for individuals with previous SARS-CoV-2 infection, serological studies to determine basal titers may be important, independent of when diagnosis occurred.

FUNDING

Tucumán Public Health System (SIPROSA), Argentinean National Research Council (CONICET), National University of Tucumán (UNT).

Long Term Immune Response Produced by the SputnikV Vaccine

SputnikV is a vaccine against SARS-CoV-2 developed by the Gamaleya National Research Centre for Epidemiology and Microbiology. The vaccine has been shown to induce both humoral and cellular immune responses, yet the mechanisms remain largely unknown. Forty SputnikV vaccinated individuals were included in this study which aimed to demonstrate the location of immunogenic domains of the SARS-CoV-2 S protein using an overlapping peptide library. Additionally, cytokines in the serum of vaccinated and convalescent COVID-19 patients were analyzed. We have found antibodies from both vaccinated and convalescent sera bind to immunogenic regions located in multiple domains of SARS-CoV-2 S protein, including Receptor Binding Domain (RBD), N-terminal Domain (NTD), Fusion Protein (FP) and Heptad Repeats (HRs). Interestingly, many peptides were recognized by immunized and convalescent serum antibodies and correspond to conserved regions in circulating variants of SARS-CoV-2. This breadth of reactivity was still evident 90 days after the first dose of the vaccine, showing that the vaccine has induced a prolonged response. As evidenced by the activation of T cells, cellular immunity strongly suggests the high potency of the SputnikV vaccine against SARS-CoV-2 infection.

Dynamics of SARS-CoV-2-specific antibodies among COVID19 biobank donors in Argentina

Biobanks are instrumental for accelerating research. Early in SARS-CoV-2 pandemic, the Argentinean Biobank of Infectious Diseases (BBEI) initiated the COVID19 collection and started its characterization. Blood samples from subjects with confirmed SARS-CoV-2 infection either admitted to health institutions or outpatients, were enrolled. Highly exposed seronegative individuals, were also enrolled. Longitudinal samples were obtained in a subset of donors, including persons who donated plasma for therapeutic purposes (plasma donors). SARS-CoV-2-specific IgM and IgG levels, IgG titers and IgG viral neutralization capacity were determined. Out of 825 donors, 57.1% were females and median age was 41 years (IQR 32-53 years). Donors were segregated as acute or convalescent donors, and mild versus moderate/severe disease donors. Seventy-eight percent showed seroconversion to SARS-CoV-2 specific antibodies. Specific IgM and IgG showed comparable positivity rates in acute donors. IgM detectability rate declined in convalescent donors while IgG detectability remained elevated in early (74,8%) and late (83%) convalescent donors. Among donors with follow-up samples, IgG levels seemed to decline more rapidly in plasma donors. IgG levels were higher with age, disease severity, number of symptoms, and more durable in moderate/severe disease donors. Levels and titers of anti-spike/RBD IgG strongly correlated with neutralization activity against WT virus. The BBEI-COVID19 collection serves a dual role in this SARS-CoV-2 global crisis. First, it feeds researchers and developers transferring samples and data to fuel research projects. Second, it generates highly needed local data to understand and frame the regional dynamics of the infection.

Controversy surrounding the Sputnik V vaccine

The Sputnik V COVID-19 vaccine is a member of the so-called vector vaccines and uses two different vectors (Ad26 priming and Ad5 boost) to reduce the risk of a reduction in the effectiveness of the vaccination. Real life data indicate an efficacy of the vaccine above 97%. Low cost and no need for ultra-cold storage temperature temperatures are other pluses of the Sputnik V vaccine. However, there are also several important shortcomings that must be considered such as the possible reduction of its immunogenicity in the presence of very high Ad5 neutralizing antibody titres and the decrease with age of the antibody titres neutralizing the virus. Furthermore, there is emerging documentation that Sputnik V has a reduced neutralizing capacity against the Beta variant and all variants with the spike protein carrying the E484K substitution. Nevertheless, due to its characteristics, Sputnik V could be another useful means of satisfying the need for mass vaccination. However, it is imperative to document the efficacy and safety of the Sputnik V vaccine in individuals with high pre-existing anti-Ad26 and Ad5-neutralizing antibody titres and in those under the age of 18 or older than 60 years and be certain that Sputnik V does not cause the rare development of immune thrombotic thrombocytopenia. It is hoped that the now widespread use of this vaccine will generate a large pragmatic real-world study with data accessible to anyone interested in verifying them.

The Rise of Vectored Vaccines: A Legacy of the COVID-19 Global Crisis

The COVID-19 pandemic represents a milestone in vaccine research and development in a global context. A worldwide effort, as never seen before, involved scientists from all over the world in favor of the fast, accurate and precise construction and testing of immunogens against the new coronavirus, SARS-CoV-2. Among all the vaccine strategies put into play for study and validation, those based on recombinant viral vectors gained special attention due to their effectiveness, ease of production and the amplitude of the triggered immune responses. Some of these new vaccines have already been approved for emergency/full use, while others are still in pre- and clinical trials. In this article we will highlight what is behind adeno-associated vectors, such as those presented by the immunogens ChaAdOx1, Sputnik, Convidecia (CanSino, Tianjin, China), and Janssen (Johnson & Johnson, New Jersey, EUA), in addition to other promising platforms such as Vaccinia virus MVA, influenza virus, and measles virus, among others.