Neutralizing Antibody Responses to SARS-CoV-2 in Korean Patients Who Have Recovered from COVID-19

Effective Neutralizing Antibody Response Against SARS-CoV-2 Virus and Its Omicron BA.1 Variant in Fully Vaccinated Hematological Patients

SARS-CoV-2 and its variants cause CoronaVIrus Disease 19 (COVID-19), a pandemic disease. Hematological malignancies increase susceptibility to severe COVID-19 due to immunosuppression. Anti-SARS-CoV-2 neutralizing antibodies protect against severe COVID-19. This retrospective real-life study aimed to evaluate seropositivity and neutralizing antibody rates against SARS-CoV-2 and its Omicron BA.1 variant in hematological patients. A total of 106 patients with different hematologic malignancies, who have mostly received three or more vaccine doses (73%), were included in this study. Serum was collected between May and June 2022. The primary endpoint was anti-SARS-CoV-2 antibody response against ancestral (wild type; wt) and Omicron BA.1 virus, defined as a neutralizing antibody titer ≥ 1:10. Adequate neutralizing antibody response was observed in 75 (71%) and 87 (82%) of patients for wt and Omicron BA.1 variants, respectively.However, patients with B-cell lymphoproliferative disorders and/or those treated with anti-CD20 monoclonal antibodies in the prior 12 months showed a lower seropositivity rate compared to other patients against both Omicron BA.1 variant (73% vs 91%; P = 0.02) and wt virus (64% vs 78%; P = 0.16). Our real-life experience confirmed that full vaccination against SARS-CoV-2 induces adequate neutralizing antibody protection for both the wt virus and Omicron BA.1 variants, even in hematological frail patients. However, protective measures should be maintained in hematological patients, especially those with B-cell lymphoproliferative diseases treated with anti-CD20 monoclonal antibodies, because these subjects could have a reduced neutralizing antibody production.

Change in Severity and Clinical Manifestation of MIS-C Over SARS-CoV-2 Variant Outbreaks in Korea

BACKGROUND

There is difference in the incidence of multi-system inflammatory syndrome in children (MIS-C) in patients with different variants of severe acute respiratory syndrome coronavirus 2, however, little is known about the epidemiology in Asian countries. We investigated and compared the epidemiology of the MIS-C during omicron-dominant period with that of previous periods in South Korea.

METHODS

We obtained clinical, epidemiological and laboratory data on MIS-C cases from national MIS-C surveillance in South Korea. We defined pre-delta period as January 2020-May 2021; delta period as June 2021-December 2021; and omicron period as January 2022-April 2022. We describe the clinical characteristics and outcomes of MIS-C patients by period.

RESULTS

A total of 91 cases were assessed to be MIS-C cases. Number of MIS-C cases have increased from six cases during pre-delta period to 66 cases during omicron period, while the incidence rate (the number of MIS-C cases per 100,000 cases of reported coronavirus disease 2019) has decreased from 38.5 cases per 100,000 (95% confidence interval [CI], 14.1-83.9) during pre-delta period to 1.6 cases per 100,000 (95% CI, 1.2-2.0) during omicron periods. During pre-delta period, 66.7% and 100% had hypotension and gastrointestinal involvement, respectively; while during omicron period, 12.1% and 6.1% had such clinical manifestations. Fifty percent of pre-delta MIS-C patients were taken intensive care unit (ICU) cares, while 10.6% of patients during omicron periods were in ICUs.

CONCLUSION

Omicron period were associated with less severe clinical manifestation compared to pre-delta and delta periods. Although incidence rate of MIS-C was lower for the omicron period than pre-delta and delta periods, number of patients reported with MIS-C may pose a substantial clinical burden.

Corrigendum to "The prevalence and long-term health effects of long Covid among hospitalised and non-hospitalised populations: a systematic review and meta-analysis"

[This corrects the article DOI: 10.1016/j.eclinm.2022.101762.].

Complete blood count derived inflammatory biomarkers and the level of anti-SARS-CoV-2 NAb and S-RBD IgG among cancer survivors receiving COVID-19 vaccines

<b>Background</b>: In the era of coronavirus disease 2019 (COVID-19), it is mandatory to identify vulnerable people with cancers as they have impaired immune system that can lead to high mortality. This study analyzes the complete blood count (CBC) derived inflammatory biomarkers and the level of anti-SARS-CoV-2 neutralizing antibody (NAb) and spike protein’s receptor-binding domain immunoglobulin G (S-RBD IgG) among cancer survivors.<br /> <b>Methods</b>: A cross-sectional study was conducted in patients with either solid or hematological cancers who had received two-doses of COVID-19 vaccinations within six months.<br /> <b>Results</b>: From 119 subjects, the COVID-19 vaccines demonstrated laboratory efficacy (median NAb=129.03 AU/mL; median S-RBD IgG=270.53 AU/mL). The seropositive conversion of NAb reached 94.1% and S-RBD IgG reached 93.3%. Additionally, the S-RBD IgG had very weak correlation with absolute monocyte count (R=-0.185; <i>p</i>-value=0.044). The NAb also had very weak correlation with leukocyte (Kendall’s tau-b (τb)=-0.147; <i>p</i>-value=0.019), absolute neutrophil count (τb=-0.126; <i>p</i>-value=0.044), absolute eosinophil count (τb=-0.132; <i>p</i>-value=0.034).<br /> <b>Conclusion</b>: The seropositivity rate of anti-SARS-CoV-2 NAb and S-RBD IgG were significantly high. However, the CBC derived inflammatory biomarkers had poor correlation with anti-SARS-CoV-2 NAb and S-RBD IgG. Thus, anti-SARS-CoV-2 NAb and S-RBD IgG are currently the only reliable markers for measuring the COVID-19 vaccine efficacy which should be widely accessible.

Performance Evaluation of RapiSure (EDGC) COVID-19 S1 RBD IgG/Neutralizing Ab Test for the Rapid Detection of SARS-CoV-2 Antibodies

The accurate detection of anti-neutralizing SARS-CoV-2 antibodies can aid in the understanding of the development of protective immunity against COVID-19. This study evaluated the diagnostic performance of the RapiSure (EDGC) COVID-19 S1 RBD IgG/Neutralizing Ab Test. Using the 90% plaque reduction neutralization test (PRNT₉₀) as a reference, 200 serum samples collected from 78 COVID-19-positive and 122 COVID-19-negative patients were divided into 76 PRNT₉₀-positive and 124 PRNT₉₀-negative groups. The ability of the RapiSure test to detect antibodies was compared to that of the STANDARD Q COVID-19 IgM/IgG Plus test and that of PRNT₉₀. The positive, negative, and overall percent agreement between the RapiSure and STANDARD Q test was 95.7%, 89.3%, and 91.5%, respectively, with a Cohen's kappa of 0.82. The RapiSure neutralizing antibody test results revealed a sensitivity of 93.4% and a specificity of 100% compared to the PRNT results, with an overall percent agreement of 97.5% and Cohen's kappa of 0.95. The diagnostic performance of the RapiSure test was in good agreement with the STANDARD Q COVID-19 IgM/IgG Plus test and comparable to that of the PRNT. The RapiSure S1 RBD IgG/Neutralizing Ab Test was found to be convenient and reliable and, thus, can provide valuable information for rapid clinical decisions during the COVID-19 pandemic.

Analysis of Factors Affecting Neutralizing Antibody Production after COVID-19 Vaccination Using Newly Developed Rapid Point-of-Care Test

(1) Objective: To investigate the factors that affect rates of neutralizing antibody production and duration after vaccination using the newly developed SARS-CoV-2 POCT. (2) Methods: The production of immunoglobulin and neutralizing antibody in clinical subjects who completed various vaccines was analyzed using the POCT, the semi-quantitative was interpreted by measurement application, and the quantified neutralizing antibody titers were using the ELISA. (3) Results: According to the clinical performance analysis of the POCT, the clinical sensitivity and the specificity were 96.8% (90/93) and 97.7% (167/171), respectively, for the S1 RBD IgG antibody. The clinical sensitivity was 92.22% (83/90), and the clinical specificity was 100.00% (174/174) for neutralizing antibodies. Factors influencing antibody production were analyzed using the whole blood of the five types of second-completed vaccinators (N = 736, 20−80 years old). General and neutralizing antibody and showed significant differences in age (p < 0.0001), vaccine type (p < 0.0001), inoculation interval (p < 0.0001), pain score (p < 0.0001), diabetes (p < 0.0001), and hypertension (p = 0.002). The gender (p = 0.021) and chronic fatigue (p = 0.02) did not show the significance. (4) Conclusions: An acquisition of immunoglobulin and neutralizing antibody varies according to vaccine type, age, days after vaccination, pain degree after vaccination, and underlying diseases. The POCT used in this study will be utilized for clinical recommendations such as deciding whether to receive additional vaccines through the immediate rapid determination of neutralizing antibody generation in the clinical site.

Performance Evaluation of the BZ COVID-19 Neutralizing Antibody Test for the Culture-Free and Rapid Detection of SARS-CoV-2 Neutralizing Antibodies

Rapid and accurate measurement of SARS-CoV-2 neutralizing antibodies (nAbs) can aid in understanding the development of immunity against COVID-19. This study evaluated the diagnostic performance of a rapid SARS-CoV-2 nAb detection test called the BZ COVID-19 nAb test BZ-nAb (BZ-nAb; BioZentech). Using the 90% plaque-reduction neutralization test (PRNT-90) as a reference, 104 serum specimens collected from COVID-19-positive and -negative patients were grouped into 40 PRNT-90-positive and 64 PRNT-90-negative specimens. The performance of the BZ-nAb was compared with that of the cPass surrogate virus neutralization test (cPass sVNT; Genscript). The BZ-nAb showed a sensitivity ranging from 92.5%-95.0% and specificity ranging from 96.9%-100%, whereas cPass sVNT showed a sensitivity of 100% (95% confidence interval (CI) 90.5%-100%) and specificity of 98.4% (95% CI, 91.6%-100%). The dilution factor obtained with PRNT-90 showed a stronger correlation with the percent inhibition of cPass sVNT (r = 0.8660, p < 0.001) compared with the test and control line ratio (T/C ratio) of the BZ-nAb (r = -0.7089, p < 0.001). An almost perfect agreement was seen between the BZ-nAb and cPass sVNT results, with a strong negative correlation between the BZ-nAb T/C ratio and cPass sVNT percent inhibition (r = -0.8022, p < 0.001). In conclusion, the diagnostic performance of the BZ-nAb was comparable to that of the cPass sVNT, although the BZ-nAb had a slightly lower sensitivity.

SARS-CoV-2 Antibody Response to the BNT162b2 mRNA Vaccine in Persons with Past Natural Infection

There are still no agreed guidelines on the vaccination of coronavirus disease 2019 (COVID-19) for previously infected patients. Here, we present two seropositive healthcare workers (HCWs) working in an isolation ward who recovered from COVID-19 in April 2020 and got vaccinated with BNT162b2 vaccine in March 2021. We have assessed the clinical course, vaccine-related adverse events, and antibody response after natural infection and after first and second dose vaccination. One of the two HCWs was asymptomatic during quarantine, but the other had mild upper respiratory infection symptoms 1 day before admission, and the symptoms continued for 9 days. There was no pneumonic infiltration in chest X-ray in both patients, and no COVID-19 specific treatment was administered. Total immunoglobulin antibody and neutralizing antibody to anti-spike protein receptor-binding domain of severe acute respiratory syndrome coronavirus 2 were confirmed to be present in both HCWs in blood tests performed at 2 weeks and 4 weeks after discharge. Antibody response to mRNA vaccination showed marked elevation after the first vaccination, which was 30-40 times higher than that of antibody titer after natural infection in each patient (83.2 U/mL vs. > 2,500 U/mL in patient 1; 61.6 U/mL vs. > 2,500 U/mL in patient 2). Signal inhibition rate of neutralizing antibodies was also increased to over 97%. Due to this increased effect, there was little difference in antibody levels after the first and second dose. Both patients 1 and 2 suffered more from adverse vaccine reactions after the second vaccination than from COVID-19 symptoms.