Persistence of Antibodies Against Spike Glycoprotein of SARS-CoV-2 in Healthcare Workers Post Double Dose of BBV-152 and AZD1222 Vaccines

Purpose: We investigated the persistence of the vaccine-induced immunoglobulin G (IgG) antibodies against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) among healthcare workers (HCWs) in Odisha who received a complete dose of either Covaxin or Covishield vaccine.Methods: This 24-week longitudinal cohort study was conducted from January to July 2021 with participants from 6 healthcare and research facilities of Odisha to understand the dynamicity of the vaccine-induced IgG antibodies against SARS-CoV-2 after the complete dose of vaccines.Results: Serum samples were collected from 614 participants during each follow-up and were tested in two chemiluminescent microparticle immunoassay (CLIA)-based platforms to detect SARS-CoV-2 antibodies both qualitatively and quantitatively. Among these participants, 308 (50.2%) participants were Covishield recipients and the rest 306 (49.8%) participants took Covaxin. A total of 81 breakthrough cases were recorded and the rest 533 HCWs without any history of postvaccination infection showed significant antibody waning either from T3 (Covaxin recipient) or T4 (Covishield recipient). The production of vaccine-induced IgG antibodies is significantly higher (p < 0.001) in Covishield compared with Covaxin. Covishield recipients produced higher median anti-S IgG titer than Covaxin. No statistically significant differences in antibody titers were observed based on age, gender, comorbidities, and blood groups.Conclusion: This 6-month follow-up study documents a 2-fold and 4-fold decrease in spike antibody titer among Covishield and Covaxin recipients, respectively. The clinical implications of antibody waning after vaccination are not well understood. It also highlights the need for further data to understand the long-term persistence of vaccine-induced antibody and threshold antibody titer required for protection against reinfection.

Testing Antigens, Antibodies, and Immune Cells in COVID-19 as a Public Health Topic—Experience and Outlines

The current COVID-19 pandemic has triggered an accelerated pace in all research domains, including reliable diagnostics methodology. Molecular diagnostics of the virus and its presence in biological samples relies on the RT-PCR method, the most used and validated worldwide. Nonconventional tests with improved parameters that are in the development stages will be presented, such as droplet digital PCR or CRISPR-based assays. These molecular tests were followed by rapid antigen testing along with the development of antibody tests, whether based on ELISA platform or on a chemiluminescent microparticle immunoassay. Less-conventional methods of testing antibodies (e.g., lateral flow immunoassay) are presented as well. Left somewhere in the backstage of COVID-19 research, immune cells and, furthermore, immune memory cells, are gaining the spotlight, more so in the vaccination context. Recently, methodologies using flow-cytometry evaluate circulating immune cells in infected/recovered patients. The appearance of new virus variants has triggered a surge for tests improvement. As the pandemic has entered an ongoing or postvaccination era, all methodologies that are used to monitor public health focus on diagnostic strategies and this review points out where gaps should be filled in both clinical and research settings.

Vitamin D Levels among Hospitalized and Non-Hospitalized COVID-19 Patients in Dr. M. Djamil General Hospital Padang

Coronavirus Disease 2019 (COVID-19) causes immune system dysregulation and an exaggerated systemic inflammatory response. Vitamin D acts as an immunomodulator that enhances the immunity defense. Low levels of vitamin D affect the severity of COVID-19 infection. This study aims to determine vitamin D levels in hospitalized and non-hospitalized COVID-19 patients. A case-control study was conducted involving 62 COVID-19 patients, equally divided into hospitalized and non-hospitalized groups at RSUP dr. M. Djamil, Padang from February to September 2020. Serum vitamin D levels were measured using the Chemiluminescent Microparticle Immunoassay. Vitamin D deficiency was defined as a level less than 20 ng/mL. The hospitalized group consisted of moderate to critical COVID-19 patients, whereas the non-hospitalized group consisted of the asymptomatic and mild COVID-19 patients according to the Indonesian Ministry of Health Guidelines. All data were analyzed using a T-test and Chi-square with a significant p-value of 0.05. The results showed that most subjects were women between 21–60 years. The mean level of vitamin D (ng/mL) in the hospitalized group was lower than in the non-hospitalized group (15.5 ± 7.72 vs. 19.2 ± 14.30; 95% CI -9.509–2.167; p=0.213). Vitamin D deficiency affected hospitalized group more than the non-hospitalized group, but not statistically significant (71% vs. 64.5%, p=0.566). It indicated the role of vitamin D in preventing immune system hyperactivation causing COVID-19 cytokine storm. This study concluded no difference in vitamin D levels among the study groups. Nevertheless, further research on vitamin D is needed to determine its role and benefits against COVID-19 infection.

Dynamics of Antibody Response to BNT162b2 mRNA COVID-19 Vaccine: A 7-Month Follow-Up Study

Background and Objectives: Comprehension regarding immunity to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is limited, and the durability of immune responses after vaccination is currently unknown. Several studies have reported on the antibody response in fully vaccinated individuals with a limited follow-up of the participants, i.e., below 7 months. Materials and Methods: The antibody response to complete vaccination with the BNT162b2 mRNA COVID-19 vaccine was assessed monthly, for 7 months, in 92 healthcare workers, between February 26 and September 26, 2021. The SARS-CoV-2 anti-spike protein IgG (IgGS) antibody was detected using the SARS-CoV-2 IgG II Quant assay (Abbott, Diagnostics Division, Sligo, Ireland), a chemiluminescent microparticle immunoassay (CMIA) with a sensitivity of 98.1% and specificity of 99.6%. Participants were divided into two groups, one for individuals previously infected with SARS-CoV-2 and the other for individuals without previous infection. Results: The median IgGS titers decreased monthly both in previously infected individuals and in the uninfected group. Previously infected individuals had significantly higher median titers of IgGS compared with previously uninfected subjects at all seven time points after complete vaccination (p < 0.001). Conclusions: Seven months after vaccination, the median IgGS titer had decreased by more than 92% both in individuals previously infected with SARS-CoV-2 and in uninfected individuals. However, IgGS antibodies were still detected in all study participants and persisted throughout the 7 months after the second dose of the vaccine. Further studies should be conducted to monitor the antibody response to the BNT162b2 mRNA vaccine beyond 7 months, to assess the need for a new booster dose in order to extend the duration and amplitude of the specific immune response.

Long-term specific IgG response to SARS-CoV-2 nucleocapsid protein in recovered COVID-19 patients

This study monitored the long-term immune response to severe acute respiratory syndrome coronavirus (SARS-CoV)-2 infection in patients who had recovered from coronavirus disease (COVID)-19. Anti-nucleocapsid immunoglobulin G (anti-N IgG) titer in serum samples collected at a single (N = 302) or multiple time points (N = 229) 3–12 months after COVID-19 symptom onset or SARS-CoV-2 detection in respiratory specimens was measured by semiquantitative chemiluminescent microparticle immunoassay. The 531 patients (966 specimens) were classified according to the presence or absence of pneumonia symptoms. Anti N IgG was detected in 87.5% of patients (328/375) at 3 months, 38.6% (93/241) at 6 months, 23.7% (49/207) at 9 months, and 26.6% (38/143) at 12 months. The anti-N IgG seropositivity rate was significantly lower at 6, 9, and 12 months than at 3 months (P < 0.01) and was higher in the pneumonia group than in the non-pneumonia/asymptomatic group at 6 months (P < 0.01), 9 months (P = 0.04), and 12 months (P = 0.04). The rate started to decline 6–12 months after symptom onset. Anti-N IgG sample/cutoff index was positively correlated with age (r = 0.192, P < 0.01) but negatively correlated with interval between symptom onset and blood sampling (r = − 0.567, P < 0.01). These findings can guide vaccine strategies in recovered COVID-19 patients.

Humoral responses to SARS-CoV-2 mRNA vaccines: Role of past infection

Two mRNA vaccines (BNT162b2 and mRNA-1273) against severe acute respiratory syndrome-coronavirus 2 (SARS-CoV-2) are globally authorized as a two-dose regimen. Understanding the magnitude and duration of protective immune responses is vital to curbing the pandemic. We enrolled 461 high-risk health services workers at the University of California, Los Angeles (UCLA) and first responders in the Los Angeles County Fire Department (LACoFD) to assess the humoral responses in previously infected (PI) and infection naïve (NPI) individuals to mRNA-based vaccines (BNT162b2/Pfizer- BioNTech or mRNA-1273/Moderna). A chemiluminescent microparticle immunoassay was used to detect antibodies against SARS-CoV-2 Spike in vaccinees prior to (n = 21) and following each vaccine dose (n = 246 following dose 1 and n = 315 following dose 2), and at days 31–60 (n = 110) and 61–90 (n = 190) following completion of the 2-dose series. Both vaccines induced robust antibody responses in all immunocompetent individuals. Previously infected individuals achieved higher median peak titers (p = 0.002) and had a slower rate of decay (p = 0.047) than infection-naïve individuals. mRNA-1273 vaccinated infection-naïve individuals demonstrated modestly higher titers following each dose (p = 0.005 and p = 0.029, respectively) and slower rates of antibody decay (p = 0.003) than those who received BNT162b2. A subset of previously infected individuals (25%) required both doses in order to reach peak antibody titers. The biologic significance of the differences between previously infected individuals and between the mRNA-1273 and BNT162b2 vaccines remains uncertain, but may have important implications for booster strategies.

Prevalence of SARS-CoV-2 antibodies in healthy blood donors from the state of Tyrol, Austria, in summer 2020

Summary Background Seroepidemiological studies provide important insight into the spread of severe acute respiratory syndrome coronavirus 2 (SARS-CoV‑2) in our society. We aimed to determine seropositivity of SARS-CoV‑2 antibodies and its cross-sectional correlates in a large cohort of blood donors. Methods In this observational cohort study, we tested healthy blood donors residing in Tyrol, Austria, for SARS-CoV‑2 antibodies using the Abbott SARS-CoV‑2 IgG chemiluminescent microparticle immunoassay. We estimated 95% confidence intervals (95% CI) of seroprevalences using bootstrapping and tested for differences by participant characteristics using logistic regression. Findings Between 8 June and 4 September 2020, we screened 5345 healthy individuals at local blood donor sessions (mean age 42.7 years, SD 13.5 years, 46.7% female). Overall seroprevalence was 3.1% (95% CI 2.7–3.6%, 165 cases), which is 5.1-fold higher (95% CI 4.5–6.0%) than the case number identified by the health authorities in the state-wide testing program (0.6%; 4536 out of 757,634). Seroprevalence was higher in the district Landeck (16.6%, P < 0.001) and in individuals aged < 25 years (4.7%, P = 0.043), but did not differ by gender, blood types, or medication intake. The odds ratio for seropositivity was 2.51 for participants who had travelled to Ischgl (1.49–4.21, P = 0.001), 1.39 who had travelled to other federal states (1.00–1.93, P = 0.052), and 2.41 who had travelled abroad (1.61–3.63, P < 0.001). Compared to participants who had a suspected/confirmed SARS-CoV‑2 infection but were seronegative, seropositive participants more frequently reported loss of smell (odds ratio = 2.49, 1.32–4.68, P = 0.005) and taste (odds ratio = 2.76, 1.54–4.92, P = 0.001). Conclusion In summer 2020, SARS-CoV‑2 seroprevalence in Tyrolean blood donors was 3.1%. Our study revealed regional variation and associations with young age, travel history and specific symptoms.

Severe Acute Respiratory Syndrome Coronavirus-2 Seropositivity in South-Central Uganda, During 2019 - 2021

Background: Globally, key subpopulations such as healthcare workers (HCWs) have a higher risk of contracting SARS-CoV-2. In Uganda, limited access to personal protective equipment amidst lack of clarity on the extent and pattern of the community disease burden may exacerbate this situation. We assessed SARS-CoV-2 antibody seroprevalence among high-risk sub-populations in South-central Uganda, including HCWs, persons within the general population previously reporting experiencing key COVID-19 like symptoms (fever, cough, loss of taste and smell) and archived plasma specimens collected between October 2019 – 18th March 2020, prior to confirmation of COVID-19 in Uganda.Methods: From November 2020 - January 2021, we collected venous blood from HCWs at selected health facilities in South-Central Uganda and from population-cohort participants who reported specific COVID-19 like symptoms in a prior phone-based survey conducted (between May to August 2020) during the first national lockdown. Pre-lockdown plasma collected (between October 2019 and March 18th, 2020) from individuals considered high risk for SARS-CoV-2 infection was retrieved. Specimens were tested for antibodies to SARS-CoV-2 using the CoronaChekTM rapid COVID-19 IgM/IgG lateral flow test assay. IgM only positive samples were confirmed using a chemiluminescent microparticle immunoassay (CMIA) (Architect AdviseDx SARS-CoV-2 IgM) which targets the spike protein. SARS-CoV-2 exposure was defined as either confirmed IgM, both IgM and IgG or sole IgG positivity.Results: The seroprevalence of antibodies to SARS-CoV-2 in HCWs was 21.1% [95%CI: 18.2-24.2]. Of the phone-based survey participants, 11.9% [95%CI: 8.0-16.8] had antibodies to SARS-CoV-2. Among 636 pre-lockdown plasma specimens, 1.7% [95%CI: 0.9-3.1] were reactive. Conclusions: Findings suggest a high seroprevalence of antibodies to SARS-CoV-2 among HCWs and substantial exposure in persons presenting with specific COVID-19 like symptoms in the general population of South-central Uganda. Based on current limitations in serological test confirmation, it remains unclear whether pre-lockdown seropositivity implies prior SARS-CoV-2 exposure in Uganda.

Chemiluminescent Microparticle Immunoassay for the Diagnosis of Congenital Chagas Disease: A Prospective Study in Spain

Congenital Chagas disease (CCD) has become a global health problem. Historically, the diagnosis of CCD has been carried out using parasitological methods and traditional serological techniques, however, new serological techniques such as chemiluminescent microparticle immunoassays (CMIA) have been developed in the last few years with many advantages compared with traditional serological tests. A total of 75 children born to 72 Latin American Chagas-infected mothers were consecutively enrolled and studied by CMIA and indirect immunofluorescence (IIF) at 0–2, 6, 9, and 12 months of age. At the end of the follow-up, 74 out of 75 children were considered uninfected and one child was diagnosed with CCD. Our study emphasizes the need to carry out serological follow-up on every newborn from a mother with Chagas disease and shows that CMIA assay is a great diagnostic tool as a single serological test at 9 months of age to rule out CCD or to identify possible transmission.