Limited Correlation between SARS-CoV-2 Serologic Assays for Identification of High-Titer COVID-19 Convalescent Plasma Using FDA Thresholds

Longitudinal Qualitative and Quantitative Evaluation of SARS-CoV-2 Antibodies in Immunized Health Care Workers

CONTEXT.—

Many studies have depended on qualitative antibody assays to investigate questions related to COVID-19 infection, vaccination, and treatment.

OBJECTIVE.—

To evaluate immunoglobulin G (IgG) levels in vaccinated individuals over time and characterize limitations of qualitative and quantitative antibody assays.

DESIGN.—

Longitudinal serum samples (n = 339) were collected from 72 health care workers vaccinated against COVID-19. SARS-CoV-2 IgG levels before, during, and after vaccination were measured by using a qualitative anti-spike protein IgG assay and a quantitative anti-S1 IgG assay. Assay results were compared to understand antibody dynamics related to vaccination.

RESULTS.—

Qualitative testing demonstrated 100% seroconversion after the first vaccine dose, peak IgG levels after the second vaccine dose, and a progressive 50% decline during the next 8 months. Quantitative testing demonstrated that IgG levels during and after vaccination were above the analytical measurement range.

CONCLUSIONS.—

Qualitative testing demonstrates expected changes in SARS-CoV-2 IgG levels related to sequential vaccine doses and time since antigen exposure. However, proportional changes in the associated numerical signals are very likely inaccurate. Adoption of standardized quantitative SARS-CoV-2 antibody testing with a broad analytical measurement range is essential to determine a correlate of protection from COVID-19 that can be scaled for widespread use.

The value of observational registry studies for the next infectious disease emergency

During infectious disease emergencies, it may be necessary to deploy new therapies without conclusive evidence for their effectiveness. During the SARS-CoV-2 pandemic, several countries used registries to track the use of COVID-19 convalescent plasma (CCP). Those registries provided evidence that CCP was effective when used early and with high titer.

Rates Among Hospitalized Patients With COVID-19 Treated With Convalescent Plasma: A Systematic Review and Meta-Analysis

Objective

To examine the association of COVID-19 convalescent plasma transfusion with mortality and the differences between subgroups in hospitalized patients with COVID-19.

Patients and Methods

On October 26, 2022, a systematic search was performed for clinical studies of COVID-19 convalescent plasma in the literature from January 1, 2020, to October 26, 2022. Randomized clinical trials and matched cohort studies investigating COVID-19 convalescent plasma transfusion compared with standard of care treatment or placebo among hospitalized patients with confirmed COVID-19 were included. The electronic search yielded 3841 unique records, of which 744 were considered for full-text screening. The selection process was performed independently by a panel of 5 reviewers. The study followed the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. Data were extracted by 5 independent reviewers in duplicate and pooled using an inverse-variance random effects model. The prespecified end point was all-cause mortality during hospitalization.

Results

Thirty-nine randomized clinical trials enrolling 21,529 participants and 70 matched cohort studies enrolling 50,160 participants were included in the systematic review. Separate meta-analyses reported that transfusion of COVID-19 convalescent plasma was associated with a decrease in mortality compared with the control cohort for both randomized clinical trials (odds ratio [OR], 0.87; 95% CI, 0.76-1.00) and matched cohort studies (OR, 0.76; 95% CI, 0.66-0.88). The meta-analysis of subgroups revealed 2 important findings. First, treatment with convalescent plasma containing high antibody levels was associated with a decrease in mortality compared with convalescent plasma containing low antibody levels (OR, 0.85; 95% CI, 0.73 to 0.99). Second, earlier treatment with COVID-19 convalescent plasma was associated with a decrease in mortality compared with the later treatment cohort (OR, 0.63; 95% CI, 0.48 to 0.82).

Conclusion

During COVID-19 convalescent plasma use was associated with a 13% reduced risk of mortality, implying a mortality benefit for hospitalized patients with COVID-19, particularly those treated with convalescent plasma containing high antibody levels treated earlier in the disease course.

Impact of the COVID-19 pandemic on blood donation and transfusions in the United States in 2020

INTRODUCTION

Reports have suggested the COVID-19 pandemic resulted in blood donation shortages and adverse impacts on the blood supply. Using data from the National Blood Collection and Utilization Survey (NBCUS), we quantified the pandemic's impact on red blood cell (RBC) and apheresis platelet collections and transfusions in the United States during year 2020.

METHODS

The 2021 NBCUS survey instrument was modified to include certain blood collection and utilization variables for 2020. The survey was distributed to all US blood collection centers, all US hospitals performing ≥1000 surgeries annually, and a 40% random sample of hospitals performing 100-999 surgeries annually. Weighting and imputation were used to generate national estimates for whole blood and apheresis platelet donation; RBC and platelet transfusion; and convalescent plasma distribution.

RESULTS

Whole blood collections were stable from 2019 (9,790,000 units; 95% CI: 9,320,000-10,261,000) to 2020 (9,738,000 units; 95% CI: 9,365,000-10,110,000). RBC transfusions decreased by 6.0%, from 10,852,000 units (95% CI: 10,444,000-11,259,000) in 2019 to 10,202,000 units (95% CI: 9,811,000-10,593,000) in 2020. Declines were steepest during March-April 2020, with transfusions subsequently rebounding. Apheresis platelet collections increased from 2,359,000 units (95% CI: 2,240,000-2,477,000) in 2019 to 2,408,000 units (95% CI: 2,288,000-2,528,000) in 2020. Apheresis platelet transfusions increased from 1,996,000 units (95% CI: 1,846,000-2,147,000) in 2019 to 2,057,000 units (95% CI: 1,902,000-2,211,000) in 2020.

CONCLUSION

The COVID-19 pandemic resulted in reduced blood donations and transfusions in some months during 2020 but only a minimal annualized decline compared with 2019.

Commentary on "Outcomes of Convalescent Plasma with Defined High versus Lower Neutralizing Antibody Titers against SARS-CoV-2 among Hospitalized Patients: CoronaVirus Inactivating Plasma (CoVIP) Study"

The totality of evidence favors the efficacy of convalescent plasma to treat COVID-19 when high-titer plasma is administered early in the course of disease or to immunocompromised patients. In this commentary, we frame the findings of L. A. Bartelt, A. J. Markmann, B. Nelson, J. Keys, et al. (mBio 13:e01751-22, 2022, https://doi.org/10.1128/mBio.01751-22) in the context of the normal approval process for a therapeutic product. We point out that convalescent plasma has taken all of the typical steps associated with approval for a therapeutic product. Additionally, in less than 3 years, the optimal use cases and continued utility of this product to treat COVID-19 have been defined.

Validation of Viral Inactivation Protocols for Therapeutic Blood Products against Severe Acute Respiratory Syndrome Coronavirus-2 (SARS-COV-2)

Therapeutic blood products including convalescent plasma/serum and immunoglobulins concentrated from convalescent plasma, such as intravenous immunoglobulins or hyperimmune globulins, and monoclonal antibodies are passive immunotherapy options for novel coronavirus disease 2019 (COVID-19). They have been shown to improve the clinical status and biological and radiological parameters in some groups of COVID-19 patients. However, blood products are still potential sources of virus transmission in recipients. The use of pathogen reduction technology (PRT) should increase the safety of the products. The purpose of this study was to determine the impact of solvent/detergents (S/D) procedures on SARS-COV-2 infectivity elimination in the plasma of donors but also on COVID-19 convalescent serum (CCS) capacity to neutralize SARS-COV-2 infectivity. In this investigation, S/D treatment for all experiments was performed at a shortened process time (30 min). We first evaluated the impact of S/D treatments (1% TnBP/1% TritonX-45 and 1% TnBP/1% TritonX-100) on the inactivation of SARS-COV-2 pseudoparticles (SARS-COV-2pp)-spiked human plasma followed by S/D agent removal using a Sep-Pak Plus C18 cartridge. Both treatments were able to completely inactivate SARS-COV-2pp infectivity to an undetectable level. Moreover, the neutralizing activity of CCS against SARS-COV-2pp was preserved after S/D treatments. Our data suggested that viral inactivation methods using such S/D treatments could be useful in the implementation of viral inactivation/elimination processes of therapeutic blood products against SARS-COV-2.