Humoral Immune Response Induced by the BBIBP-CorV Vaccine (Sinopharm) in Healthcare Workers: A Cohort Study

Comparison of immune response to SARS-COV-2 vaccine in COVID-recovered versus non-infected Individuals

To determine the antibody levels at 6 months in SARS-CoV-2 vaccinated individuals in COVID-recovered versus non-infected groups to determine the need to administer booster COVID vaccine in each group. Prospective longitudinal study. Pathology Department, Combined Military Hospital, Lahore for a period of eight months from July 2021 to February 2022. Two hundred and thirty three study participants in both COVID recovered and non-infected groups (105 participants in infected group, 128 participants in non-infected group) were subjected to blood sampling at 6 months post-vaccination. Anti-SARS-CoV-2 IgG antibody test was done using Chemiluminescence method. Comparison of antibody levels between COVID-recovered and non-infected groups was made. Results were compiled and statistically analyzed using SPSS version 21. Out of 233 study participants, males were 183 (78%) while females were 50 (22%), mean age being 35.93 years ± 8.298. Mean Anti-SARS-CoV-2 S IgG levels among COVID-recovered group was 1342 U/ml and among non-infected group was 828 U/ml at 6 months post-vaccination. Mean antibody titers in COVID-19 recovered group are higher than in non-infected group at 6 months post-vaccination in both groups.

Analysis of COVID-19 Incidence and Protective Potential of Persisting IgG Class Antibodies against SARS-CoV-2 Infection in Hospital Staff in Poland

The immune responses to both SARS-CoV-2 infection and vaccines are of key importance in prevention efforts. In April and May 2020, 703 study participants tested for COVID-19 by PCR tests were registered. In June and July 2020, they were examined for the presence of SARS-CoV-2 S1/S2 IgG. From October 2020 to January 2021, those among the study population with COVID-19 confirmed by PCR tests were registered, and the same group of participants was invited to be examined again for the presence of SARS-CoV-2 antibodies. In June 2020, antibodies were detected in only 88% of those who had PCR-confirmed COVID-19 in April-May 2020, which suggests that a significant proportion of persons in the Polish population do not produce antibodies after contact with SARS-CoV-2 antigens or rapidly lose them and reach levels below the lab detection limit. The levels of IgG class anti-SARS-CoV-2 antibodies were significantly lower among people who previously had COVID-19 than for those who had received COVID-19 vaccination, which confirms the high immunogenicity of the vaccines against COVID-19 in the Polish population. The study confirms that a detectable level of IgG class anti-SARS-CoV-2 antibodies cannot be considered a reliable marker of the presence and strength of COVID-19 immunity preventing individuals from acquiring SARS-CoV-2 infection.

Neutralizing Antibodies as Predictors of Vaccine Breakthrough Infection in Healthcare Workers Vaccinated with or without a Heterologous Booster Dose: A Cohort Study during the Third COVID-19 Wave in Peru

We evaluated neutralizing antibody (NAbs) levels as a protective factor against vaccine breakthrough infection (VBI) in healthcare workers (HCWs) during the third COVID-19 wave in Peru. This retrospective cohort study employed the information from a private laboratory in Lima (Peru) of HCW who received only two BBIBP-CorV vaccines or (additionally) a heterologous booster with BNT162b2. We evaluated the association between the VBI and the levels of NAbs at 21, 90, 180, and 210 days after the BBIBP-CorV second dose. NAbs were calculated with the cPass™ SARS-CoV-2 Neutralization Antibody Detection kit (surrogate virus neutralization test (sVNT)) and the Elecsys^® anti-SARS-CoV-2 S Test. Of the 435 HCW evaluated, 31.72% had an infection previous to vaccination, 68.28% received a booster dose, and 23.21% had a VBI during the third wave. The variables associated with a lower risk of VBI were male sex (aRR: 0.43) and those who had (180 days after BBIBP-CorV inoculation) NAbs levels ≥ 60% (aRR: 0.58) and ≥90% (aRR: 0.59) on cPass™, and ≥500 with Elecsys^® (aRR: 0.58). HCW whose NAbs persisted at higher levels six months after the BBIBP-CorV showed a lower risk of suffering from a VBI during the third COVID-19 wave.

Homologous booster immunization with an inactivated vaccine induced robust antibody response in healthcare workers: A retrospective study

Coronavirus Disease 2019 (Covid-19) severely impacted the health, society, and economy around the world. With declining protective efficacy of primary vaccination and the spread of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) variants, a Covid-19 booster vaccination is being fully implemented globally. Many people received three doses of BBIBP-CorV inactivated vaccine in China and other developing countries. However, the antibody response and immune persistence of the homologous BBIBP-CorV booster vaccination is yet to be thoroughly evaluated, as previous studies focused within one month after the third dose. In this study, 97 participants were enrolled to analyze the antibody response and immune persistence within 6 months as well as the safety within 7 days after the third-dose of homologous BBIBP-CorV inactivated vaccine. The seroconversion rate for total antibody against the receptor binding domain (RBD) of the SARS-CoV-2 spike (S) protein were both 100% at month 1 and month 6 after the third dose. The IgG against the RBD of the SARS-CoV-2 S protein seroconversion rate increased from 42.27% before the third dose to 100% 1 month after the third dose and then slightly decreased to 98.97% 5 months later. Positive IgM against the RBD of the SARS-CoV-2 S protein was rare and was observed in only one participant at month 1 after the third dose. The neutralizing antibody levels at month 1 and month 6 after the third dose increased 63.32-fold and 13.16-fold compared with those before the third dose, and the positive rate for neutralizing antibody was still 100% at month 6 after the third dose. Importantly, the antibody responses induced by the vaccine and immune persistence were not affected by sex or age. No serious adverse reactions were reported. Total antibody and IgG against the RBD of the SARS-CoV-2 S protein were highly correlated with neutralizing antibody, suggesting that total antibody and IgG against the RBD of the SARS-CoV-2 S protein could be used as predictors for neutralizing antibody. In conclusion, the third dose of homologous BBIBP-CorV inactivated vaccine induced a robust antibody response and moderate immune persistence. These finding are of great significance for development future vaccination strategies.

One-Year Post-Vaccination Longitudinal Follow-Up of Quantitative SARS-CoV-2 Anti-Spike Total Antibodies in Health Care Professionals and Evaluation of Correlation with Surrogate Neutralization Test

Numerous vaccines have been generated to decrease the morbidity and mortality of COVID-19. This study aims to evaluate the immunogenicity of the heterologous boosts by BioNTech against homologous boosts by CoronaVac at three-month intervals in two health care worker (HCW) cohorts, with or without prior COVID-19, for one year post-vaccination. This is a prospective cohort study in which the humoral responses of 386 HCWs were followed-up longitudinally in six main groups according to their previous COVID-19 exposure and vaccination status. Anti-SARS-CoV-2 spike-RBD total antibody levels were measured and SARS-CoV-2 neutralization antibody (NAbs) responses against the ancestral Wuhan and the Omicron variant were evaluated comparatively using international standard serum for Wuhan and Omicron, as well as with the aid of a conversion tool. The anti-SARS-CoV-2 spike-RBD total Ab and Nab difference between with and without prior COVID-19, three months after two-dose primary vaccination with CoronaVac, was statistically significant (p = 0.001). In the subsequent follow-ups, this difference was not observed between the groups. Those previously infected (PI) and non-previously infected (NPI) groups receiving BioNTech as the third dose had higher anti-SARS-CoV-2 spike total Ab levels (14.2-fold and 17.4-fold, respectively, p = 0.001) and Nab responses (against Wuhan and Omicron) than those receiving CoronaVac. Ab responses after booster vaccination decreased significantly in all groups at the ninth-month follow-up (p < 0.05); however, Abs were still higher in all booster received groups than that in the primary vaccination. Abs were above the protective level at the twelfth-month measurement in the entire of the second BioNTech received group as the fourth dose of vaccination. In the one-year follow-up period, the increased incidence of COVID-19 in the groups vaccinated with two or three doses of CoronaVac compared with the groups vaccinated with BioNTech as a booster suggested that continuing the heterologous CoronaVac/BioNTech vaccination, revised according to current SARS-CoV-2 variants and with at least a six-month interval booster would be an effective and safe strategy for protection against COVID-19, particularly in health care workers.

Utility of Roche Elecsys anti-SARS-CoV-2 S in ascertaining post-vaccine neutralizing antibodies

With widespread global COVID-19 vaccine coverage, a scalable, cost-effective, and standardized tool to ascertain post-vaccine immunity is a dire need. Neither clinical evaluations of vaccine efficacy, nor live virus antibody neutralization assays fulfill these criteria. Commercially available anti-S binding immunological assays have the potential to fill this gap, but need to be systematically evaluated for their utility to serve as surrogates for the aforementioned, widely accepted tools of determining vaccine efficacy. In this study, we evaluated an anti-S binding immunological assay (Roche Elecsys Anti-SARS-CoV-2 S) by utilizing two hundred and fifty-five archived serum specimens, either pre-pandemic, or those exposed to natural infections or vaccines with their neutralizing titers pre-determined through a live virus, pseudotyped antibody neutralization assay. Roche Elecsys Anti-SARS-CoV-2 S demonstrated good sensitivity (98%) and specificity (99%), just as has been reported in some other previously conducted studies using this assay. Only a mild correlation, however, with the live virus pseudotyped lentivirus antibody neutralization assay (Spearman's r = 0.26) was observed. We conclude that, as such, Elecsys Anti-SARS-CoV-2 S has a high sensitivity and specificity for detecting anti-SARS-CoV-2 S proteins, though the assay does not always correlate well with live virus assays for quantitative outcomes.

An Immunological Review of SARS-CoV-2 Infection and Vaccine Serology: Innate and Adaptive Responses to mRNA, Adenovirus, Inactivated and Protein Subunit Vaccines

The coronavirus disease 2019 (COVID-19) pandemic is caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) virus, which is defined by its positive-sense single-stranded RNA (ssRNA) structure. It is in the order Nidovirales, suborder Coronaviridae, genus Betacoronavirus, and sub-genus Sarbecovirus (lineage B), together with two bat-derived strains with a 96% genomic homology with other bat coronaviruses (BatCoVand RaTG13). Thus far, two Alphacoronavirus strains, HCoV-229E and HCoV-NL63, along with five Betacoronaviruses, HCoV-HKU1, HCoV-OC43, SARS-CoV, MERS-CoV, and SARS-CoV-2, have been recognized as human coronaviruses (HCoVs). SARS-CoV-2 has resulted in more than six million deaths worldwide since late 2019. The appearance of this novel virus is defined by its high and variable transmission rate (RT) and coexisting asymptomatic and symptomatic propagation within and across animal populations, which has a longer-lasting impact. Most current therapeutic methods aim to reduce the severity of COVID-19 hospitalization and virus symptoms, preventing the infection from progressing from acute to chronic in vulnerable populations. Now, pharmacological interventions including vaccines and others exist, with research ongoing. The only ethical approach to developing herd immunity is to develop and provide vaccines and therapeutics that can potentially improve on the innate and adaptive system responses at the same time. Therefore, several vaccines have been developed to provide acquired immunity to SARS-CoV-2 induced COVID-19-disease. The initial evaluations of the COVID-19 vaccines began in around 2020, followed by clinical trials carried out during the pandemic with ongoing population adverse effect monitoring by respective regulatory agencies. Therefore, durability and immunity provided by current vaccines requires further characterization with more extensive available data, as is presented in this paper. When utilized globally, these vaccines may create an unidentified pattern of antibody responses or memory B and T cell responses that need to be further researched, some of which can now be compared within laboratory and population studies here. Several COVID-19 vaccine immunogens have been presented in clinical trials to assess their safety and efficacy, inducing cellular antibody production through cellular B and T cell interactions that protect against infection. This response is defined by virus-specific antibodies (anti-N or anti-S antibodies), with B and T cell characterization undergoing extensive research. In this article, we review four types of contemporary COVID-19 vaccines, comparing their antibody profiles and cellular aspects involved in coronavirus immunology across several population studies.

Host Protective Immunity against Severe Acute Respiratory Coronavirus 2 (SARS-CoV-2) and the COVID-19 Vaccine-Induced Immunity against SARS-CoV-2 and Its Variants

The world is now apparently at the last/recovery stage of the COVID-19 pandemic, starting from 29 December 2019, caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). With the progression of time, several mutations have taken place in the original SARS-CoV-2 Wuhan strain, which have generated variants of concern (VOC). Therefore, combatting COVID-19 has required the development of COVID-19 vaccines using several platforms. The immunity induced by those vaccines is vital to study in order to assure total protection against SARS-CoV-2 and its emerging variants. Indeed, understanding and identifying COVID-19 protection mechanisms or the host immune responses are of significance in terms of designing both new and repurposed drugs as well as the development of novel vaccines with few to no side effects. Detecting the immune mechanisms for host protection against SARS-CoV-2 and its variants is crucial for the development of novel COVID-19 vaccines as well as to monitor the effectiveness of the currently used vaccines worldwide. Immune memory in terms of the production of neutralizing antibodies (NAbs) during reinfection is also very crucial to formulate the vaccine administration schedule/vaccine doses. The response of antigen-specific antibodies and NAbs as well as T cell responses, along with the protective cytokine production and the innate immunity generated upon COVID-19 vaccination, are discussed in the current review in comparison to the features of naturally induced protective immunity.