SARS-CoV-2 Serological Studies around the Globe

A special issue of Vaccines (ISSN 2076-393X). This special issue belongs to the section "COVID-19 Vaccines and Vaccination".

Deadline for manuscript submissions: closed (31 May 2021) | Viewed by 235389

Special Issue Editors

1. Department of Hygiene, Epidemiology and Medical Statistics, Medical School, National and Kapodistrian University of Athens, 11527 Athens, Greece
2. Hellenic Scientific Society for the Study of AIDS, Sexually Transmitted and Emerging Diseases, 11527 Athens, Greece
Interests: public health; epidemiology; epidemiology of viral infections; viral hepatitis; SARS-CoV-2; people who inject drugs; respondent driven sampling; preventive medicine
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

A novel coronavirus (2019-nCoV) associated with human to human transmission and severe human infection has been recently reported from the city of Wuhan in the Hubei province in China. A total of 13.4 and 0.58 million cases and deaths, respectively, were reported up to 16 July 2020. Given the high transmissibility and the extensive geographic dispersal of the virus as well as the absence of effective treatments or a vaccine, public health measures provide the only way to prevent SARS-CoV-2 transmission. The contribution of asymptomatic individuals to onward transmissions is significant and has been highlighted in previous studies. Given that SARs-CoV-2 is a new virus, we need to better understand the levels and the duration of protective immunity in patients with different severities of the disease (i.e., asymptomatic, mild and severe symptoms, hospitalized patients, ARDS symptoms), the levels of exposure to SARS-CoV-2 in highly vulnerable people and populations of special interest (i.e., healthcare workers, migrants, intravenous drug users, populations with limited access to health care facilities, HIV/AIDS patients), the parameters associated with the presence of antibodies, as well as the estimated performance of antibody testing in panels with known SARS-CoV-2 status. All of this information will be valuable across different geographic areas and different time periods.

Prof. Angelos Hatzakis
Dr. Dimitrios Paraskevis
Guest Editors

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Keywords

  • SARS-CoV-2
  • COVID-19
  • antibodies
  • immune response
  • attack rate
  • seroepidemiology
  • epidemiology
  • immunity
  • IgG
  • IgM
  • IgA
  • antibody titers
  • long-term immune response
  • protective immunity
  • vaccine
  • vulnerable populations
  • seroconversion time

Published Papers (19 papers)

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Research

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12 pages, 1366 KiB  
Article
Usefulness of IVD Kits for the Assessment of SARS-CoV-2 Antibodies to Evaluate the Humoral Response to Vaccination
Vaccines 2021, 9(8), 840; https://doi.org/10.3390/vaccines9080840 - 31 Jul 2021
Cited by 29 | Viewed by 3658
Abstract
Background: The introduction of the vaccination against SARS-CoV-2 infection creates the need for precise tools for the quality control of vaccination procedures, detection of poor humoral response, and estimation of the achieved protection against the disease. Thus, the study aimed to compare the [...] Read more.
Background: The introduction of the vaccination against SARS-CoV-2 infection creates the need for precise tools for the quality control of vaccination procedures, detection of poor humoral response, and estimation of the achieved protection against the disease. Thus, the study aimed to compare the results of the anti-SARS-CoV-2 tests to evaluate the application of the WHO standard unitage (the binding antibody units; BAU/mL) for a measurement of response to the vaccination. Methods: Patients undergoing vaccination against SARS-CoV-2 with Pfizer/BioNTech BNT162b2 (BNT162b2) (n = 79), referred for SARS-CoV-2 antibody measurement prior to vaccination and 21 days after dose 1, and 8, 14, and 30 days after dose 2 were included. The sera were tested with three assays: Elecsys SARS-CoV-2 S (Roche), LIAISON® SARS-CoV-2 TrimericS IgG (DiaSorin), and SARS-CoV-2 IgG II Quant (Abbott). Results: The three assays showed varying correlations at different time points in the study. The overall agreement for all samples was moderate to high (ρ = 0.663–0.902). We observed the most uniform agreement for the day of dose 2 (ρ = 0.775–0.825), while it was least consistent for day 8 (ρ = −0.131–0.693) and 14 (ρ = −0.247–0.603) after dose 2. The dynamics of changes of the SARS-CoV-2 antibody levels in patients without history of prior SARS-CoV-2 infection appears homogenous based on the Roche results, more heterogenous when considering the DiaSorin results, and in between for the Abbott results. Conclusions: The results highlight the need for further work on the international standard of measurement of SARS-CoV-2 Ig, especially in the era of vaccination. The serological assays can be useful to detect IgG/IgM antibodies to assess the response to the vaccination. However, they cannot be used interchangeably. In terms of the evaluation of the immune response to the BNT162b2 vaccine, Roche and Abbott kits appear to be more useful. Full article
(This article belongs to the Special Issue SARS-CoV-2 Serological Studies around the Globe)
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20 pages, 7571 KiB  
Article
Effect of Professional and Extra-Professional Exposure on Seroprevalence of SARS-CoV-2 Infection among Healthcare Workers of the French Alps: A Multicentric Cross-Sectional Study
Vaccines 2021, 9(8), 824; https://doi.org/10.3390/vaccines9080824 - 27 Jul 2021
Cited by 9 | Viewed by 1679
Abstract
We aimed to report SARS-CoV-2 seroprevalence after the first wave of the pandemic among healthcare workers, and to explore factors associated with an increased infection rate. We conducted a multicentric cross-sectional survey from 27 June to 31 September 2020. For this survey, we [...] Read more.
We aimed to report SARS-CoV-2 seroprevalence after the first wave of the pandemic among healthcare workers, and to explore factors associated with an increased infection rate. We conducted a multicentric cross-sectional survey from 27 June to 31 September 2020. For this survey, we enrolled 3454 voluntary healthcare workers across four participating hospitals, of which 83.4% were female, with a median age of 40.6 years old (31.8–50.3). We serologically screened the employees for SARS-CoV-2, estimated the prevalence of infection, and conducted binomial logistic regression with random effect on participating hospitals to investigate associations. We estimated the prevalence of SARS-CoV-2 infection at 5.0% (95 CI, 4.3%–5.8%). We found the lowest prevalence in health professional management support (4.3%) staff. Infections were more frequent in young professionals below 30 years old (aOR = 1.59, (95 CI, 1.06–2.37)), including paramedical students and residents (aOR = 3.38, (95 CI, 1.62–7.05)). In this group, SARS-CoV-2 prevalence was up 16.9%. The location of work and patient-facing role were not associated with increased infections. Employees reporting contacts with COVID-19 patients without adequate protective equipment had a higher rate of infection (aOR = 1.66, (95 CI, 1.12–2.44)). Aerosol-generating tasks were associated with a ~1.7-fold rate of infection, regardless of the uptake of FFP2. Those exposed to clusters of infected colleagues (aOR = 1.77, (95 CI, 1.24–2.53)) or intra-familial COVID-19 relatives (aOR = 2.09, (95 CI, 1.15–3.80)) also had a higher likelihood of infection. This report highlights that a sustained availability of personal protective equipment limits the SARS-CoV-2 infection rate to what is measured in the general population. It also pinpoints the need for dedicated hygiene training among young professionals, justifies the systematic eviction of infected personnel, and stresses the need for interventions to increase vaccination coverage among any healthcare workers. Full article
(This article belongs to the Special Issue SARS-CoV-2 Serological Studies around the Globe)
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9 pages, 1172 KiB  
Article
Antibodies Responses to SARS-CoV-2 in a Large Cohort of Vaccinated Subjects and Seropositive Patients
Vaccines 2021, 9(7), 714; https://doi.org/10.3390/vaccines9070714 - 01 Jul 2021
Cited by 22 | Viewed by 3959
Abstract
COVID-19 is a current global threat, and the characterization of antibody response is vitally important to update vaccine development and strategies. In this study we assessed SARS-CoV-2 antibody concentrations in SARS-CoV-2 positive patients (N = 272) and subjects vaccinated with the BNT162b2 m-RNA [...] Read more.
COVID-19 is a current global threat, and the characterization of antibody response is vitally important to update vaccine development and strategies. In this study we assessed SARS-CoV-2 antibody concentrations in SARS-CoV-2 positive patients (N = 272) and subjects vaccinated with the BNT162b2 m-RNA COVID-19 vaccine (N = 1256). For each participant, socio-demographic data, COVID-19 vaccination records, serological analyses, and SARS-CoV-2 infection status were collected. IgG antibodies against S1/S2 antigens of SARS-CoV-2 were detected. Almost all vaccinated subjects (99.8%) showed a seropositivity to anti-SARS-COV-2 IgG and more than 80% of vaccinated subjects had IgG concentrations > 200 AU/mL. In a Tobit multivariable regression analysis, SARS-CoV-2 vaccination was statistically significantly associated with increased IgG concentrations (β coef = 266.4; p < 0.001). A statistically significant reduction in SARS-CoV-2 IgG concentrations was found with older age (β coef = −1.96 per year increase; p < 0.001), male sex (β coef = −22.3; p < 0.001), and days after immunization (β coef = −1.67 per day increase; p < 0.001). Our findings could support the vaccination campaigns confirming the high immunogenicity of the SARS-CoV-2 vaccine under investigation with respect to the natural infection. Further studies will be required for evaluating the role of age and days after immunization in the persistence of vaccine antibodies and protection from the disease. Full article
(This article belongs to the Special Issue SARS-CoV-2 Serological Studies around the Globe)
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10 pages, 672 KiB  
Article
High Prevalence of Anti-PF4 Antibodies Following ChAdOx1 nCov-19 (AZD1222) Vaccination Even in the Absence of Thrombotic Events
Vaccines 2021, 9(7), 712; https://doi.org/10.3390/vaccines9070712 - 01 Jul 2021
Cited by 25 | Viewed by 6653
Abstract
It is unclear whether the ChAdOx1 nCov-19 vaccine can induce the development of anti-PF4 antibodies in vaccinated individuals who have not developed thrombosis. The aim of this prospective study was to evaluate the presence of antibodies against heparin/PF4 in adults who received a [...] Read more.
It is unclear whether the ChAdOx1 nCov-19 vaccine can induce the development of anti-PF4 antibodies in vaccinated individuals who have not developed thrombosis. The aim of this prospective study was to evaluate the presence of antibodies against heparin/PF4 in adults who received a first dose of the ChAdOx1 nCov-19 vaccine, and correlate them with clinical data and antibody responses to the vaccine. We detected non-platelet activating anti-PF4 antibodies in 67% (29/43) of the vaccinated individuals on day 22 following the first dose of the ChAdOx1 nCov-19 vaccine, though these were detected in low titers. Furthermore, there was no correlation between the presence of anti-PF4 IgG antibodies and the baseline clinical characteristics of the patients. Our findings suggest that the ChAdOx1 nCov-19 vaccine can elicit anti-PF4 antibody production even in recipients without a clinical manifestation of thrombosis. The presence of anti-PF4 antibodies was not sufficient to provoke clinically evident thrombosis. Our results offer an important insight into the ongoing investigations regarding the underlying multifactorial pathophysiology of thrombotic events induced by the ChAdOx1 nCov-19 vaccine. Full article
(This article belongs to the Special Issue SARS-CoV-2 Serological Studies around the Globe)
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9 pages, 363 KiB  
Article
Neutralizing Anti-SARS-CoV-2 Antibody Titer and Reported Adverse Effects, in a Sample of Italian Nursing Home Personnel after Two Doses of the BNT162b2 Vaccine Administered Four Weeks Apart
Vaccines 2021, 9(6), 652; https://doi.org/10.3390/vaccines9060652 - 15 Jun 2021
Cited by 24 | Viewed by 4337
Abstract
Background: The immunization of healthcare workers (HCWs) plays a recognized key role in prevention in the COVID-19 pandemic: in Italy, the vaccination campaign began at the end of December 2020. A better knowledge of the on-field immune response in HCWs, of adverse effects [...] Read more.
Background: The immunization of healthcare workers (HCWs) plays a recognized key role in prevention in the COVID-19 pandemic: in Italy, the vaccination campaign began at the end of December 2020. A better knowledge of the on-field immune response in HCWs, of adverse effects and of the main factors involved is fundamental. Methods: We performed a study on workers at a nursing home in Northern Italy, vaccinated in January–February 2021 with two doses of the BNT162b2 vaccine four weeks apart, instead of the three weeks provided for in the original manufacturer protocol. One month after the second dose, the serological titer of IgG-neutralizing anti-RBD antibodies of the subunit S1 of the spike protein of SARS-CoV-2 was determined. The socio-demographic and clinical characteristics of the subjects and adverse effects of vaccination were collected by questionnaire. Results: In all of the workers, high antibody titer, ranging between 20 and 760 times the minimum protective level were observed. Titers were significantly higher in subjects with a previous COVID-19 diagnosis. Adverse effects after the vaccine were more frequent after the second dose, but no severe adverse effects were observed. Conclusions: The two doses of the BNT162b2 vaccine, even if administered four weeks apart, induced high titers of anti-SARS-CoV-2 neutralizing IgG in all the operators included in the study. Full article
(This article belongs to the Special Issue SARS-CoV-2 Serological Studies around the Globe)
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12 pages, 4820 KiB  
Article
Seroprevalence of SARS-CoV-2 Antibodies in Symptomatic Individuals Is Higher than in Persons Who Are at Increased Risk Exposure: The Results of the Single-Center, Prospective, Cross-Sectional Study
Vaccines 2021, 9(6), 627; https://doi.org/10.3390/vaccines9060627 - 09 Jun 2021
Cited by 7 | Viewed by 2509
Abstract
The present study aimed to assess antibody seropositivity prevalence among symptomatic individuals and individuals with a high risk of occupational exposure to SARS-CoV-2. Participants from Chelyabinsk (Russian Federation) who were at an increased risk of exposure to SARS-CoV-2 (high-risk group, n = 1091) [...] Read more.
The present study aimed to assess antibody seropositivity prevalence among symptomatic individuals and individuals with a high risk of occupational exposure to SARS-CoV-2. Participants from Chelyabinsk (Russian Federation) who were at an increased risk of exposure to SARS-CoV-2 (high-risk group, n = 1091) and participants who either had symptoms consistent with COVID-19 or were suspected to have experienced COVID-19 in the past (symptomatic group, n = 692) were enrolled between 28 September and 30 December 2020. Blood samples were tested by enzyme-linked immunosorbent assay D-5501 SARS-Cov-2-IgG-EIA-BEST and D-5502 SARS-Cov-2-IgM-EIA-BEST (AO Vector-Best, Novosibirsk, Russia). The overall seropositivity rate was 28.33–28.53%. SARS-CoV-2 antibodies were detected in 17.23% (adjusted prevalence of 17.17–17.29%) of participants in the high-risk and 45.95% (adjusted prevalence of 45.91–46.24%) in the symptomatic group. Higher IgG and IgM titers were observed in women compared to men, as well as in participants in the symptomatic group compared to those in the high-risk group. The results indicate that the seroprevalence among residents in several Russian regions is low (28.38%) and inadequate to provide herd immunity. The lower seroprevalence among participants in the high-risk group may be attributed to the enforcement of healthcare protocols and the use of adequate personal protective equipment. Full article
(This article belongs to the Special Issue SARS-CoV-2 Serological Studies around the Globe)
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10 pages, 6565 KiB  
Article
Characterization of Immune Responses to SARS-CoV-2 and Other Human Pathogenic Coronaviruses Using a Multiplex Bead-Based Immunoassay
Vaccines 2021, 9(6), 611; https://doi.org/10.3390/vaccines9060611 - 07 Jun 2021
Cited by 4 | Viewed by 2441
Abstract
Serological assays that simultaneously detect antibodies to multiple targets of SARS-CoV-2 and to other structurally related coronaviruses provide a holistic picture of antibody response patterns. Well-validated multiplex immunoassays are scarce. Here, we evaluated the performance of an 11-plex serological assay capable of detecting [...] Read more.
Serological assays that simultaneously detect antibodies to multiple targets of SARS-CoV-2 and to other structurally related coronaviruses provide a holistic picture of antibody response patterns. Well-validated multiplex immunoassays are scarce. Here, we evaluated the performance of an 11-plex serological assay capable of detecting antibodies directed to four antigenic targets of SARS-CoV-2 and to S1 proteins of other human pathogenic coronaviruses. We used 620 well-characterized sera (n = 458 seropositive and n = 110 seronegative for SARS-CoV-2 in the pre-SARS-CoV-2 era and n = 52 seronegative for SARS-CoV-2 in the era of SARS-CoV-2) as positive and negative standards. We calculated the sensitivity, specificity, as well as positive and negative predictive values, including a 95% confidence interval. The difference in mean fluorescence intensity (95% CI) was used to assess a potential cross-reaction between antibodies to SARS-CoV-2 and the other coronaviruses. The sensitivity (95% CI) of detecting anti-SARS-CoV-2 antibodies to four antigenic targets ranged from 83.4% (76.7–86.7) to 93.7% (91.0–95.7) and the specificity from 98.2% (93.6–99.8) to 100% (96.7–100). We observed no obvious cross-reaction between anti-SARS-CoV-2 antibodies and antibodies to the other coronaviruses except for SARS-CoV-1. The high sensitivity and specificity warrant a reliable utilization of the assay in population-based seroprevalence surveys or vaccine efficacy studies. Full article
(This article belongs to the Special Issue SARS-CoV-2 Serological Studies around the Globe)
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12 pages, 2694 KiB  
Article
Titers, Prevalence, and Duration of SARS-CoV-2 Antibodies in a Local COVID-19 Outbreak and Following Vaccination
Vaccines 2021, 9(6), 587; https://doi.org/10.3390/vaccines9060587 - 02 Jun 2021
Cited by 7 | Viewed by 4901
Abstract
Information concerning the development of neutralizing antibodies and their duration will be critical to establishing herd immunity for COVID-19. We sought to evaluate SARS-CoV-2 spike protein receptor-binding domain (RBD)-specific antibodies, their duration, and capacity for SARS-CoV-2 neutralization in volunteers while the pandemic spread [...] Read more.
Information concerning the development of neutralizing antibodies and their duration will be critical to establishing herd immunity for COVID-19. We sought to evaluate SARS-CoV-2 spike protein receptor-binding domain (RBD)-specific antibodies, their duration, and capacity for SARS-CoV-2 neutralization in volunteers while the pandemic spread within our community starting in March 2020. Those participants with the highest starting titers had the longest-lasting response, up to 12 months post-diagnosis. SARS-CoV-2 neutralization capacity was correlated with anti-RBD antibody levels. The majority of our participants with confirmed COVID-19 diagnosis had very mild or asymptomatic infections. We also detected low and largely non-neutralizing anti-RBD IgG titers in a few participants with no known COVID-19 diagnosis. Finally, we found that antibody responses induced by vaccination were significantly higher than those induced by natural infection. Thus, our study suggests that vaccination is still critical even for those naturally infected or diagnosed with COVID-19. Full article
(This article belongs to the Special Issue SARS-CoV-2 Serological Studies around the Globe)
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10 pages, 532 KiB  
Article
Prevalence of Anti-SARS-CoV-2 Antibodies in Poznań, Poland, after the First Wave of the COVID-19 Pandemic
Vaccines 2021, 9(6), 541; https://doi.org/10.3390/vaccines9060541 - 21 May 2021
Cited by 11 | Viewed by 5564
Abstract
In comparison to other European countries, during the first months of the COVID-19 pandemic, Poland reported a relatively low number of confirmed cases of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infections. To estimate the scale of the pandemic in Poland, a serosurvey [...] Read more.
In comparison to other European countries, during the first months of the COVID-19 pandemic, Poland reported a relatively low number of confirmed cases of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infections. To estimate the scale of the pandemic in Poland, a serosurvey of antibodies against SARS-CoV-2 was performed after the first wave of COVID-19 in Europe (March–May 2020). Within this study, we collected samples from 28 July to 24 September 2020 and, based on the ELISA results, we found that 1.67% (25/1500, 95% CI 1.13–2.45) of the Poznan (Poland) metropolitan area’s population had antibodies against SARS-CoV-2 after the first wave of COVID-19. However, the presence of anti-SARS-CoV-2 IgG antibodies was confirmed with immunoblotting in 56% (14/25) samples, which finally resulted in a decrease in seroprevalence, i.e., 0.93% (14/1500, 95% CI 0.56–1.56). The positive anti-SARS-CoV-2 IgG results were associated with age, occupation involving constant contact with people, travelling abroad, non-compliance with epidemiological recommendations and direct contact with the novel coronavirus. Our findings confirm the low SARS-CoV-2 incidence in Poland and imply that the population had little herd immunity heading into the second and third wave of the pandemic, and therefore, that herd immunity contributed little to preventing the high numbers of SARS-CoV-2 infections and COVID-19-related deaths in Poland during these subsequent waves. Full article
(This article belongs to the Special Issue SARS-CoV-2 Serological Studies around the Globe)
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15 pages, 2214 KiB  
Article
Repeated Leftover Serosurvey of SARS-CoV-2 IgG Antibodies in Greece, May to August 2020
Vaccines 2021, 9(5), 504; https://doi.org/10.3390/vaccines9050504 - 13 May 2021
Cited by 4 | Viewed by 2266
Abstract
A serosurvey of IgG antibodies against SARS-CoV-2 was conducted in Greece between May and August 2020. It was designed as a cross-sectional survey and was repeated at monthly intervals. The leftover sampling methodology was used and a geographically stratified sampling plan was applied. [...] Read more.
A serosurvey of IgG antibodies against SARS-CoV-2 was conducted in Greece between May and August 2020. It was designed as a cross-sectional survey and was repeated at monthly intervals. The leftover sampling methodology was used and a geographically stratified sampling plan was applied. Of 20,110 serum samples collected, 89 (0.44%) were found to be positive for anti-SARS-CoV-2 antibodies, with higher seroprevalence (0.35%) observed in May 2020. The highest seroprevalence was primarily observed in the “30–49” year age group. Females presented higher seroprevalence compared to males in May 2020 (females: 0.58% VS males: 0.10%). This difference reversed during the study period and males presented a higher proportion in August 2020 (females: 0.12% VS males: 0.58%). Differences in the rate of seropositivity between urban areas and the rest of the country were also observed during the study period. The four-month infection fatality rate (IFR) was estimated to be 0.47%, while the respective case fatality rate (CFR) was at 1.89%. Our findings confirm low seroprevalence of COVID-19 in Greece during the study period. The young adults are presented as the most affected age group. The loss of the cumulative effect of seropositivity in a proportion of previous SARS-CoV-2 infections was indicated. Full article
(This article belongs to the Special Issue SARS-CoV-2 Serological Studies around the Globe)
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8 pages, 1464 KiB  
Communication
Immune Response to COVID-19 mRNA Vaccine—A Pilot Study
Vaccines 2021, 9(5), 488; https://doi.org/10.3390/vaccines9050488 - 11 May 2021
Cited by 18 | Viewed by 4600
Abstract
Twenty individuals (17 females, 3 males, aged 31–65 years (range), median: 46) who received both doses of the BioNTech Pfizer mRNA vaccine were examined (11 to 31 days, median: 25) after the second dose for the presence of antibodies against peptides of SARS-COV-2 [...] Read more.
Twenty individuals (17 females, 3 males, aged 31–65 years (range), median: 46) who received both doses of the BioNTech Pfizer mRNA vaccine were examined (11 to 31 days, median: 25) after the second dose for the presence of antibodies against peptides of SARS-COV-2 and some of MERS-CoV, SARS-CoV1, HCov229E, and HCoVNL63. Clinical evaluation revealed that six people had COVID-19 in the past. We found that: (i) Six people claimed the presence of unwanted effects of vaccination, which were more frequent in those with a history of COVID-19 (4 out of 6 vs. 2 out of 14, p = 0.037); (ii) All individuals independent of the past history of COVID-19 responded equally well in IgG but those who experienced the disease tended to do better in IgA class (729.04 vs. 529.78 U/mL, p = 0.079); (iii) All those who had experienced the disease had IgG antibodies against nucleocapsid antigens but also 5 out of 14 who had not had the disease (6/6 vs. 5/14, p = 0.014); (iv) Anti S2 antibodies were present in the patients having COVID-19 in the past but also were found in those who had not had the disease (6/6 vs. 8/14, p = 0.144); (v) All vaccinated people were highly positive in the IGRA and the level of released IFN gamma was correlated with the numbers of HLADR positive lymphocytes in the blood (R = 0.5766, p = 0.008). Full article
(This article belongs to the Special Issue SARS-CoV-2 Serological Studies around the Globe)
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12 pages, 1230 KiB  
Article
SARS-CoV-2 Infection Is Asymptomatic in Nearly Half of Adults with Robust Anti-Spike Protein Receptor-Binding Domain Antibody Response
Vaccines 2021, 9(3), 207; https://doi.org/10.3390/vaccines9030207 - 02 Mar 2021
Cited by 10 | Viewed by 6383
Abstract
Between June and November 2020, we assessed plasma antibodies against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) nucleocapsid protein in 4996 participants (aged 18–82 years, 34.5% men) from the National and Kapodistrian University of Athens. The weighted overall prevalence was 1.6% and monthly [...] Read more.
Between June and November 2020, we assessed plasma antibodies against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) nucleocapsid protein in 4996 participants (aged 18–82 years, 34.5% men) from the National and Kapodistrian University of Athens. The weighted overall prevalence was 1.6% and monthly prevalence correlated with viral RNA-confirmed SARS-CoV-2 infections in Greece, in the same period. Notably, 49% of seropositive cases reported no history of SARS-CoV-2 infection-related clinical symptoms and 33% were unsuspected of their previous infection. Additionally, levels of anti-SARS-CoV-2 antibodies against the spike-protein receptor-binding domain were similar between symptomatic and asymptomatic individuals, irrespective of age and gender. Using Food and Drug Administration Emergency Use Authorization-approved assays, these results support the need for such studies on pandemic evaluation and highlight the development of robust humoral immune responses even among asymptomatic individuals. The high percentage of unsuspected/asymptomatic active cases, which may contribute to community transmission for more days than that of cases who are aware and self-isolate, underscores the necessity of measures across the population for the efficient control of the pandemic. Full article
(This article belongs to the Special Issue SARS-CoV-2 Serological Studies around the Globe)
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14 pages, 1236 KiB  
Article
Delivery of mRNA Vaccine against SARS-CoV-2 Using a Polyglucin:Spermidine Conjugate
Vaccines 2021, 9(2), 76; https://doi.org/10.3390/vaccines9020076 - 21 Jan 2021
Cited by 25 | Viewed by 7408
Abstract
One of the key stages in the development of mRNA vaccines is their delivery. Along with liposome, other materials are being developed for mRNA delivery that can ensure both the safety and effectiveness of the vaccine, and also facilitate its storage and transportation. [...] Read more.
One of the key stages in the development of mRNA vaccines is their delivery. Along with liposome, other materials are being developed for mRNA delivery that can ensure both the safety and effectiveness of the vaccine, and also facilitate its storage and transportation. In this study, we investigated the polyglucin:spermidine conjugate as a carrier of an mRNA-RBD vaccine encoding the receptor binding domain (RBD) of the SARS-CoV-2 spike protein. The conditions for the self-assembling of mRNA-PGS complexes were optimized, including the selection of the mRNA:PGS charge ratios. Using dynamic and electrophoretic light scattering it was shown that the most monodisperse suspension of nanoparticles was formed at the mRNA:PGS charge ratio equal to 1:5. The average hydrodynamic particles diameter was determined, and it was confirmed by electron microscopy. The evaluation of the zeta potential of the investigated complexes showed that the particles surface charge was close to the zero point. This may indicate that the positively charged PGS conjugate has completely packed the negatively charged mRNA molecules. It has been shown that the packaging of mRNA-RBD into the PGS envelope leads to increased production of specific antibodies with virus-neutralizing activity in immunized BALB/c mice. Our results showed that the proposed polycationic polyglucin:spermidine conjugate can be considered a promising and safe means to the delivery of mRNA vaccines, in particular mRNA vaccines against SARS-CoV-2. Full article
(This article belongs to the Special Issue SARS-CoV-2 Serological Studies around the Globe)
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9 pages, 233 KiB  
Article
SARS-CoV-2 Seroprevalence Survey in People Involved in Different Essential Activities during the General Lock-Down Phase in the Province of Prato (Tuscany, Italy)
Vaccines 2020, 8(4), 778; https://doi.org/10.3390/vaccines8040778 - 19 Dec 2020
Cited by 21 | Viewed by 3686
Abstract
Serosurveys may help to assess the transmission dynamics in high-risk groups. The aim of the study was to assess the SARS-CoV-2 antibody seroprevalence in people who had performed essential activities during the lock-down period in the Province of Prato (Italy), and to evaluate [...] Read more.
Serosurveys may help to assess the transmission dynamics in high-risk groups. The aim of the study was to assess the SARS-CoV-2 antibody seroprevalence in people who had performed essential activities during the lock-down period in the Province of Prato (Italy), and to evaluate the risk of exposure to SARS-CoV-2 according to the type of service. All the workers and volunteers of the Civil Protection, employees of the municipalities, and all the staff of the Health Authority of the Province of Prato were invited to be tested with a rapid serological test. A total of 4656 participants were tested. SARS-CoV-2 antibodies were found in 138 (2.96%) cases. The seroprevalence in health care workers, in participants involved in essential support services and in those who worked from home were 4.1%, 1.4% and 1.0%, respectively. Health care workers experienced higher odds of seropositivity (OR 4.38, 95%CI 2.19–10.41) than participants who were assigned to work-from-home; no significant seropositivity differences were observed between support services and work-from-home groups. A low circulation of SARS-CoV-2 was observed among participants performing different essential activities. Findings highlighted the risk of in-hospital transmission in healthcare workers and that community support services may increase the risk of seropositivity to a limited extent in low incidence areas. Full article
(This article belongs to the Special Issue SARS-CoV-2 Serological Studies around the Globe)
10 pages, 1050 KiB  
Article
Occurrence of Antibodies against SARS-CoV-2 in the Domestic Cat Population of Germany
Vaccines 2020, 8(4), 772; https://doi.org/10.3390/vaccines8040772 - 17 Dec 2020
Cited by 71 | Viewed by 5124
Abstract
Domestic cats (Felis catus) are popular companion animals that live in close contact with their human owners. Therefore, the risk of a trans-species spreading event between domestic cats and humans is ever-present. Shortly after the emergence of the severe acute respiratory [...] Read more.
Domestic cats (Felis catus) are popular companion animals that live in close contact with their human owners. Therefore, the risk of a trans-species spreading event between domestic cats and humans is ever-present. Shortly after the emergence of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and its rapid spread around the world, the role of domestic cats in the transmission cycle was questioned. In the present study, the first large-scale survey of antibody occurrence in the domestic cat population in Germany was conducted, in order to assess the incidence of naturally occurring human to cat transmission of SARS-CoV-2. A total of 920 serum samples, which were collected from April to September of 2020, were screened by an indirect multispecies ELISA. Positive samples were verified using an indirect immunofluorescence test (iIFT) and additionally tested for neutralizing antibodies. Furthermore, serum samples were screened for antibodies against feline coronavirus (FCoV), in order to rule out cross-reactivity in the described test systems. Overall, 0.69% (6/920) of serum samples were found to be positive for antibodies against SARS-CoV-2 by ELISA and iIFT. Two of these reactive sera also displayed neutralizing antibodies. No cross-reactivity with FCoV-specific antibodies was observed. The finding of SARS-CoV-2 antibody-positive serum samples in the domestic cat population of Germany, during a period when the incidence of human infection in the country was still rather low, indicates that human-to-cat transmission of SARS-CoV-2 happens, but there is no indication of SARS-CoV-2 circulation in cats. Full article
(This article belongs to the Special Issue SARS-CoV-2 Serological Studies around the Globe)
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Review

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22 pages, 649 KiB  
Review
Vaccine Development against COVID-19: Study from Pre-Clinical Phases to Clinical Trials and Global Use
Vaccines 2021, 9(8), 836; https://doi.org/10.3390/vaccines9080836 - 29 Jul 2021
Cited by 11 | Viewed by 5374
Abstract
As per the World Health Organization (WHO), more than 288 vaccines against COVID-19 are being developed, with an estimated 184 being presently investigated in the pre-clinical phases, while 104 of these vaccine candidates are at various stages of clinical trials. Twelve of these [...] Read more.
As per the World Health Organization (WHO), more than 288 vaccines against COVID-19 are being developed, with an estimated 184 being presently investigated in the pre-clinical phases, while 104 of these vaccine candidates are at various stages of clinical trials. Twelve of these are in the advanced stages of clinical investigation, and promising results in the phase 3 trials have already paved the way for their regulatory approval and subsequent dissemination for global use. Preliminary and interim results of some of these candidate vaccines are being analyzed for public dissemination. Some of these vaccines have already been rolled out to immunize not only the highest risk individuals but also the general population in several countries. Once their safety and efficacy are established, the next limiting step would be their mass manufacturing by the pharmaceutical companies to fulfill the global demand. The challenge of manufacturing billions of doses of high-quality vaccines is under-appreciated at the moment. A massive vaccination drive would be needed to protect people of all ages. The timely and coordinated execution of the vaccination effort would require unprecedented coordination at the national and international levels for generating funds to purchase the required doses of vaccines, fair distribution of doses and managing the mechanics of delivering vaccines throughout the world. Full article
(This article belongs to the Special Issue SARS-CoV-2 Serological Studies around the Globe)
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12 pages, 1165 KiB  
Review
Population (Antibody) Testing for COVID-19—Technical Challenges, Application and Relevance, an English Perspective
Vaccines 2021, 9(6), 550; https://doi.org/10.3390/vaccines9060550 - 24 May 2021
Cited by 3 | Viewed by 2776
Abstract
In the UK, population virus or antibody testing using virus swabs, serum samples, blood spots or oral fluids has been performed to a limited extent for several diseases including measles, mumps, rubella and hepatitis and HIV. The collection of population-based infection and immunity [...] Read more.
In the UK, population virus or antibody testing using virus swabs, serum samples, blood spots or oral fluids has been performed to a limited extent for several diseases including measles, mumps, rubella and hepatitis and HIV. The collection of population-based infection and immunity data is key to the monitoring of disease prevalence and assessing the effectiveness of interventions such as behavioural modifications and vaccination. In particular, the biological properties of severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) and its interaction with the human host have presented several challenges towards the development of population-based immunity testing. Measuring SARS-CoV-2 immunity requires the development of antibody assays of acceptable sensitivity and specificity which are capable of accurately detecting seroprevalence and differentiating protection from non-protective responses. Now that anti-COVID-19 vaccines are becoming available there is a pressing need to measure vaccine efficacy and the development of herd immunity. The unprecedented impact of the SARS-CoV-2 pandemic in the UK in terms of morbidity, mortality, and economic and social disruption has mobilized a national scientific effort to learn more about this virus. In this article, the challenges of testing for SARS-CoV-2 infection, particularly in relation to population-based immunity testing, will be considered and examples given of relevant national level studies. Full article
(This article belongs to the Special Issue SARS-CoV-2 Serological Studies around the Globe)
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12 pages, 1060 KiB  
Review
Spike S2 Subunit: The Dark Horse in the Race for Prophylactic and Therapeutic Interventions against SARS-CoV-2
Vaccines 2021, 9(2), 178; https://doi.org/10.3390/vaccines9020178 - 20 Feb 2021
Cited by 19 | Viewed by 4221
Abstract
In the midst of the unceasing COVID-19 pandemic, the identification of immunogenic epitopes in the SARS-CoV-2 spike (S) glycoprotein plays a vital role in the advancement and development of intervention strategies. S is expressed on the exterior of the SARS-CoV-2 virion and contains [...] Read more.
In the midst of the unceasing COVID-19 pandemic, the identification of immunogenic epitopes in the SARS-CoV-2 spike (S) glycoprotein plays a vital role in the advancement and development of intervention strategies. S is expressed on the exterior of the SARS-CoV-2 virion and contains two subunits, namely the N-terminal S1 and C-terminal S2. It is the key element for mediating viral entry as well as a crucial antigenic determinant capable of stimulating protective immune response through elicitation of anti-SARS-CoV-2 antibodies and activation of CD4+ and CD8+ cells in COVID-19 patients. Given that S2 is highly conserved in comparison to the S1, here, we provide a review of the latest findings on the SARS-CoV-2 S2 subunit and further discuss its potential as an attractive and promising target for the development of prophylactic vaccines and therapeutic agents against COVID-19. Full article
(This article belongs to the Special Issue SARS-CoV-2 Serological Studies around the Globe)
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8 pages, 691 KiB  
Review
SARS-CoV-2 Spike Protein Elicits Cell Signaling in Human Host Cells: Implications for Possible Consequences of COVID-19 Vaccines
Vaccines 2021, 9(1), 36; https://doi.org/10.3390/vaccines9010036 - 11 Jan 2021
Cited by 38 | Viewed by 155349
Abstract
The world is suffering from the coronavirus disease 2019 (COVID-19) pandemic caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). SARS-CoV-2 uses its spike protein to enter the host cells. Vaccines that introduce the spike protein into our body to elicit virus-neutralizing antibodies [...] Read more.
The world is suffering from the coronavirus disease 2019 (COVID-19) pandemic caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). SARS-CoV-2 uses its spike protein to enter the host cells. Vaccines that introduce the spike protein into our body to elicit virus-neutralizing antibodies are currently being developed. In this article, we note that human host cells sensitively respond to the spike protein to elicit cell signaling. Thus, it is important to be aware that the spike protein produced by the new COVID-19 vaccines may also affect the host cells. We should monitor the long-term consequences of these vaccines carefully, especially when they are administered to otherwise healthy individuals. Further investigations on the effects of the SARS-CoV-2 spike protein on human cells and appropriate experimental animal models are warranted. Full article
(This article belongs to the Special Issue SARS-CoV-2 Serological Studies around the Globe)
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