High-affinity binding to the SARS-CoV-2 spike trimer by a nanostructured, trivalent protein-DNA synthetic antibody (preprint)

Multivalency enables nanostructures to bind molecular targets with high affinity. Although antibodies can be generated against a wide range of antigens, their shape and size cannot be tuned to match a given target. DNA nanotechnology provides an attractive approach for designing customized multivalent scaffolds due to the addressability and programmability of the nanostructure shape and size. Here, we design a nanoscale synthetic antibody ("nano-synbody") based on a three-helix bundle DNA nanostructure with one, two, or three identical arms terminating in a mini-binder protein that targets the SARS-CoV-2 spike protein. The nano-synbody was designed to match the valence and distance between the three receptor binding domains (RBDs) in the spike trimer, in order to enhance affinity. The protein-DNA nano-synbody shows tight binding to the wild-type, Delta, and several Omicron variants of the SARS-CoV-2 spike trimer, with affinity increasing as the number of arms increases from one to three. The effectiveness of the nano-synbody was also verified using a pseudovirus neutralization assay, with the three-arm nanostructure inhibiting two Omicron variants against which the structures with only one or two arms are ineffective. The structure of the three-arm nano-synbody bound to the Omicron variant spike trimer was solved by negative-stain transmission electron microscopy reconstruction, and shows the protein-DNA nanostructure with all three arms attached to the RBD domains, confirming the intended trivalent attachment. The ability to tune the size and shape of the nano-synbody, as well as its potential ability to attach two or more different binding ligands, will enable the high-affinity targeting of a range of proteins not possible with traditional antibodies.

A surface molecularly imprinted electrochemical biosensor for the detection of SARS-CoV-2 spike protein by using Cu7S4-Au as built-in probe.

Sensitive detection of severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) spike protein (S protein) is of significant clinical importance in the diagnosis of COVID-19 pandemic. In this work, a surface molecularly imprinted (SMI) electrochemical biosensor is fabricated for the detection of SARS-CoV-2 S protein. Cu7S4-Au is used as the built-in probe and modified on the surface of a screen-printed carbon electrode (SPCE). 4-Mercaptophenylboric acid (4-MPBA) is anchored to the surface of the Cu7S4-Au through Au-SH bonds, which can be used for the immobilization of the SARS-CoV-2 S protein template through boronate ester bonds. After that, 3-aminophenylboronic acid (3-APBA) is electropolymerized on the electrode surface and used as the molecularly imprinted polymers (MIPs). The SMI electrochemical biosensor is obtained after the elution of the SARS-CoV-2 S protein template with an acidic solution by the dissociation of the boronate ester bonds, which can be utilized for sensitive detection of the SARS-CoV-2 S protein. The developed SMI electrochemical biosensor displays high specificity, reproducibility and stability, which might be a potential and promising candidate for the clinical diagnosis of COVID-19.

Octyl gallate targeting the 3C-like protease exhibits highly efficient antiviral activity against swine enteric coronavirus PEDV.

Infection with porcine epidemic diarrhea virus (PEDV) causes severe watery diarrhea in newborn piglets, leading to substantial financial losses for the swine industry. In this study, we screened small molecule drugs targeting 3 C-like protease (3CLpro) by molecular docking, and further evaluated the antiviral activity of the screened drugs against PEDV. Results showed that octyl gallate (OG), a widely used food additive, exhibited strong binding affinity with the 3CLpro active sites of PEDV. Bio-layer interferometry and fluorescence resonance energy transfer revealed that OG directly interacts with PEDV 3CLpro (KD = 549 nM) and inhibits 3CLpro activity (IC50 = 22.15 µM). OG showed a strong inhibition of PEDV replication in vitro. Virus titers were decreased by 0.58 and 0.71 log10 TCID50/mL for the CV777 and HM2017 strains, respectively. In vivo, all piglets in the PEDV-infected group died at 48 h post-infection (hpi), while 75% of piglets in the OG treatment group showed significant relief from the clinical symptoms, pathological damage, and viral loads in the jejunum and ileum. Moreover, the western blotting results showed that OG also has strong antiviral activity against other swine enteric coronaviruses, including transmissible gastroenteritis virus (TGEV), porcine deltacoronavirus (PDCoV), and swine acute diarrhea syndrome coronavirus (SADS-CoV). Our findings revealed that OG could be developed as a novel antiviral drug against PEDV. The OG exhibited a potential broad-spectrum antiviral drug for control of other swine enteric coronaviruses.

From darkest to finest hour: recovery strategies and organizational resilience in China's hotel industry during the COVID-19 pandemic. (Special Issue: Tourism recovery under COVID-19: Experiences from China.)

In 2020, the COVID-19 pandemic adversely affected the global tourism industry and continues to impact the Chinese hotel sector today. Using a multiple cases study method, we analyzed the response strategies of four Chinese hotel groups - Jinling, Jinjiang, New Century Hotels & Resorts, and Huazhu Group Ltd. - across four successive periods: (1) outbreak;(2) first recovery;(3) struggle;and (4) a predicted finest moment. We identified four internal recovery strategies: (a) rapid response, (b) recovery exploration, (c) optimization and upgrading, and (d) rejuvenation. Hotel groups' resilience proceeded through all four stages include (re)activation, consolidation, extension, and ecosystem. Each stage demonstrated the companies' movement from reliance on internal resources to interdependence across the supply chain with on the help of digital services such as contactless check-in, robot delivery and cloud-based PMS. We additionally identified a close link between stakeholders including online travel agencies, government and hotel chains. The analysis in the present study is premised on resource utilization, product and service development, organizational management and operation, leadership, digitalization, and social responsibility. Suggestions to cope with a long-duration crisis like COVID-19 are also provided.

At-Home COVID-19 Rapid Antigen Test Down to 0.03 pg mL-1 of Nucleocapsid Protein.

Rapid and ultra-sensitive detection of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is critical for early screening and management of COVID-19. Currently, the real-time reverse transcription polymerase chain reaction (rRT-PCR) is the primary laboratory method for diagnosing SARS-CoV-2. It is not suitable for at-home COVID-19 diagnostic test due to the long operating time, specific equipment, and professional procedures. Here an all-printed photonic crystal (PC) microarray with portable device for at-home COVID-19 rapid antigen test is reported. The fluorescence-enhanced effect of PC amplifies the fluorescence intensity of the labeled probe, achieving detection of nucleocapsid (N-) protein down to 0.03 pg mL-1 . A portable fluorescence intensity measurement instrument gives the result (negative or positive) by the color of the indicator within 5 s after inserting the reacted PC microarray test card. The N protein in inactivated virus samples (with cycle threshold values of 26.6-40.0) can be detected. The PC microarray provides a general and easy-to-use method for the timely monitoring and eventual control of the global coronavirus pandemic.

Hematologic health services and practical characteristics: report of a nationwide survey among Chinese hematologists (preprint)

Background: In the past 40 years, China has experienced tremendous economic development, but the current situation of hematologists has rarely been reported. A landscape survey of human resources is essential for healthcare development and policy formulation in the future. Methods: The Chinese Society of Hematology initiated a survey of Chinese hematologists in mainland China for evaluating demographic and practice characteristics. Respondents were anonymous, and there were no limitations regarding their age, sex, etc. Results: Totally 2032 hematologists responded, with a median age bracket of 36-45 years. Respondents were well engaged into subspecialties, and 28.1% acquired doctorates of philosophy. Hematopoietic cell transplantation (HCT) centers have been established all over China. Higher-GDP regions reported more advantages, including bigger scale of transplant centers (P < 0.001), younger age structure (P = 0.039), better education qualifications (P = 0.001) and less turnover intentions (P = 0.004), despite of increased risk of medical disputes (P = 0.028). Although females accounted for 65.5% of hematologists, males were older (P < 0.001), and had more senior professional titles (P < 0.001), academic positions (P < 0.001), opportunities for continuing education (P < 0.001), and paper publishing in the recent two years (P = 0.001). For turnover intention, the higher GDP regions led to an independently reduced risk (HR = 0.673, 95%CI [0.482-0.940], P = 0.020), whereas medical disputes resulted in an increased the risk (HR = 2.037, 95%CI [1.513-2.743], P < 0.001). Considering the impact of the COVID-19 pandemic, majority of respondents believed that the decline in patient visits and delay in treatment was within 30%. 67.9% of respondents reported a decrease of the use of bone marrow as grafts but 18.8% reported an increase of cord blood units. 35.0% of the respondents switched their daily work to support the anti-epidemic medical activities. Conclusions: We concluded the discipline of hematology in China has flourished in recent years with a young workforce, while regional economic and gender disparities warrant further continuous optimization. Joint efforts against the impact of COVID-19 are needed in the post-pandemic era.

The research progress, hotspots, challenges and outlooks of solid-phase denitrification process.

Nitrogen pollution is one of the main reasons for water eutrophication. The difficulty of nitrogen removal in low-carbon wastewater poses a huge potential threat to the ecological environment and human health. As a clean biological nitrogen removal process, solid-phase denitrification (SPD) was proposed for long-term operation of low-carbon wastewater. In this paper, the progress, hotspots, and challenges of the SPD process based on different solid carbon sources (SCSs) are reviewed. Compared with synthetic SCS and natural SCS, blended SCSs have more application potential and have achieved pilot-scale application. Differences in SCSs will lead to changes in the enrichment of hydrolytic microorganisms and hydrolytic genes, which indirectly affect denitrification performance. Moreover, the denitrification performance of the SPD process is also affected by the physical and chemical properties of SCSs, pH of wastewater, hydraulic retention time, filling ratio, and temperature. In addition, the strengthening of the SPD process is an inevitable trend. The strengthening measures including SCSs modification and coupled electrochemical technology are regarded as the current research hotspots. It is worth noting that the outbreak of the COVID-19 epidemic has led to the increase of disinfection by-products and antibiotics in wastewater, which makes the SPD process face challenges. Finally, this review proposes prospects to provide a theoretical basis for promoting the efficient application of the SPD process and coping with the challenge of the COVID-19 epidemic.

Immunological and metabolic characteristics of the Omicron variants infection.

The Omicron variants of SARS-CoV-2, primarily authenticated in November 2021 in South Africa, has initiated the 5th wave of global pandemics. Here, we systemically examined immunological and metabolic characteristics of Omicron variants infection. We found Omicron resisted to neutralizing antibody targeting receptor binding domain (RBD) of wildtype SARS-CoV-2. Omicron could hardly be neutralized by sera of Corona Virus Disease 2019 (COVID-19) convalescents infected with the Delta variant. Through mass spectrometry on MHC-bound peptidomes, we found that the spike protein of the Omicron variants could generate additional CD8 + T cell epitopes, compared with Delta. These epitopes could induce robust CD8 + T cell responses. Moreover, we found booster vaccination increased the cross-memory CD8 + T cell responses against Omicron. Metabolic regulome analysis of Omicron-specific T cell showed a metabolic profile that promoted the response of memory T cells. Consistently, a greater fraction of memory CD8 + T cells existed in Omicron stimulated peripheral blood mononuclear cells (PBMCs). In addition, CD147 was also a receptor for the Omicron variants, and CD147 antibody inhibited infection of Omicron. CD147-mediated Omicron infection in a human CD147 transgenic mouse model induced exudative alveolar pneumonia. Taken together, our data suggested that vaccination booster and receptor blocking antibody are two effective strategies against Omicron.

Coronavirus-like Core-Shell-Structured Co@C for Hydrogen Evolution via Hydrolysis of Sodium Borohydride.

Constructing a reliable and robust cobalt-based catalyst for hydrogen evolution via hydrolysis of sodium borohydride is appealing but challenging due to the deactivation caused by the metal leaching and re-oxidization of metallic cobalt. A unique core-shell-structured coronavirus-like Co@C microsphere was prepared via pyrolysis of Co-MOF. This special Co@C had a microporous carbon coating to retain the reduced state of cobalt and resist the metal leaching. Furthermore, several nano-bumps grown discretely on the surface afforded enriched active centers. Applied in the pyrolysis of NaBH4, the Co@C-650, carbonized at 650 °C, exhibited the best activity and reliable recyclability. This comparable performance is ascribed to the increased metallic active sites and robust stability.

Meplazumab in hospitalized adults with severe COVID-19 (DEFLECT): a multicenter, seamless phase 2/3, randomized, third-party double-blind clinical trial.

Meplazumab, a humanized CD147 antibody, has shown favourable safety and efficacy in our previous clinical studies. In DEFLECT (NCT04586153), 167 patients with severe COVID-19 were enroled and randomized to receive three dosages of meplazumab and a placebo. Meplazumab at 0.12 mg/kg, compared to the placebo group, showed clinical benefits in significantly reducing mortality by 83.6% (2.4% vs. 14.6%, p = 0.0150), increasing the proportion of patients alive and discharged without supplemental oxygen (82.9% vs. 70.7%, p = 0.0337) and increasing the proportion of patients who achieved sustained clinical improvement (41.5% vs. 31.7%). The response rate in the 0.2 mg/kg group was relatively increased by 16.0% compared with the placebo group (53.7% vs. 46.3%). Meplazumab also reduced the viral loads and multiple cytokine levels. Compare with the placebo group, the 0.3 mg/kg significantly increased the virus negative rate by 40.6% (p = 0.0363) and reduced IL-8 level (p = 0.0460); the 0.2 mg/kg increased the negative conversion rate by 36.9%, and reduced IL-4 (p = 0.0365) and IL-8 levels (p = 0.0484). In this study, the adverse events occurred at a comparable rate across the four groups, with no unexpected safety findings observed. In conclusion, meplazumab promoted COVID-19 convalescence and reduced mortality, viral load, and cytokine levels in severe COVID-19 population with good safety profile.

Molecularly imprinted miniature electrochemical biosensor for SARS-CoV-2 spike protein based on Au nanoparticles and reduced graphene oxide modified acupuncture needle.

Accurate detection of SARS-CoV-2 spike (SARS-CoV-2-S) protein is of clinical significance for early diagnosis and timely treatment of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Herein, a surface molecularly imprinted miniature biosensor was fabricated. Au nanoparticles (AuNPs), reduced graphene oxide (rGO), poly(methylene blue)/poly(ionic liquids) and poly(ionic liquids) were successively electrodeposited onto the pinpoint of an acupuncture needle (AN). The molecularly imprinted miniature biosensor was obtained after the template of SARS-CoV-2-S protein was removed, which could be used for sensitive detection of SARS-CoV-2-S protein. The linear range and limit of detection (LOD) were 0.1 âˆ¼ 1000 ng mL-1 and 38 pg mL-1, respectively, which were superior to other molecularly imprinted biosensors previously reported. The developed miniature biosensor also exhibited high specificity and stability. The reliability of the biosensor was evaluated by the detection of SARS-CoV-2-S protein in clinical serum samples.

CD147 contributes to SARS-CoV-2-induced pulmonary fibrosis.

COVID-19 patients can develop clinical and histopathological features associated with fibrosis, but the pathogenesis of fibrosis remains poorly understood. CD147 has been identified as a universal receptor for SARS-CoV-2 and its variants, which could initiate COVID-19-related cytokine storm. Here, we systemically analyzed lung pathogenesis in SARS-CoV-2- and its delta variant-infected humanized CD147 transgenic mice. Histopathology and Transmission Electron Microscopy revealed inflammation, fibroblast expansion and pronounced fibrotic remodeling in SARS-CoV-2-infected lungs. Consistently, RNA-sequencing identified a set of fibrosis signature genes. Furthermore, we identified CD147 as a crucial regulator for fibroblast activation induced by SARS-CoV-2. We found conditional knockout of CD147 in fibroblast suppressed activation of fibroblasts, decreasing susceptibility to bleomycin-induced pulmonary fibrosis. Meplazumab, a CD147 antibody, was able to inhibit the accumulation of activated fibroblasts and the production of ECM proteins, thus alleviating the progression of pulmonary fibrosis caused by SARS-CoV-2. In conclusion, we demonstrated that CD147 contributed to SARS-CoV-2-triggered progressive pulmonary fibrosis and identified CD147 as a potential therapeutic target for treating patients with post-COVID-19 pulmonary fibrosis.

Does Real Flexibility Help Firms Navigate the COVID-19 Pandemic?

Building on the investment-based asset pricing framework, we show that firms’ ability to timely scale down their operations reduces the sensitivity of their equity value to large adverse productivity shocks. Using U.S. data in the times of the COVID-19 pandemic, we provide empirical evidence consistent with our model’s predictions. Real flexibility curbs losses in firm value and reduces return volatility, especially for firms with high book-to-market or high COVID-19 exposure, consistent with the idea that the benefits of real flexibility are associated primarily with contraction options during the COVID-19 crisis. Our analysis shows that real flexibility provides incremental and complementary protection beyond financial flexibility. Besides its impact on stock prices, real flexibility also helps firms sustain earnings during 2020, compared with 2019 when the pandemic had not struck. Our work demonstrates that real flexibility is an important tool for corporate managers in navigating episodes of disasters.

Comparative analysis of pediatric Respiratory Syncytial Virus epidemiology and clinical severity before and during the COVID-19 pandemic in British Columbia, Canada (preprint)

BackgroundThe COVID-19 pandemic affected Respiratory Syncytial Virus (RSV) circulation and surveillance, causing logistical complexity for health systems. Our objective was to describe changes in epidemiology and clinical severity of RSV cases in British Columbia, Canada. MethodsComparative analysis of RSV detections in children <36 months at BC Childrens Hospital (BCCH) between September 1 and August 31 of 2017-18, 2018-19, 2019-20, 2020-21 and 2021-22. ResultsAbout one-fifth of children tested RSV positive on average across all periods. The median age of RSV cases was 11.8 [IQR: 3.8-22.3] months in 2021-22 versus 6.3 [IQR: 1.9-16.7] months in 2017-20 (p<0.001). Increased testing in 2021-22 (n=3,120) compared to 2017-20 (average n=1,222/period) detected milder infections with lower proportion hospitalized in all age subgroups <6 (26.0%), 6-11 (12.3%), 12-23 (12.2%) and 24-35 (16.0%) months versus 2017-20 (49.3%, 53.5%, 62.6%, 57.5%, respectively) (all p<0.001). Children <6 months consistently comprised most hospitalizations and those born prematurely <29 weeks or with chronic respiratory co-morbidities remained at highest hospitalization risk in 2021-22. Among hospitalized cases, intensive care, respiratory support or supplemental oxygen use did not differ between the 2017-20 and 2021-22 periods. ConclusionsRSV circulation halted during the pandemic, but with the lifting of mitigation measures a subsequent resurgence in children <36 months of age was accompanied by shift toward older (24-35 month) cases in 2021-22, without increased severity. For the 2022-23 period, increased circulation and residual vulnerability in additional birth cohorts spared from RSV infection during the pandemic could have marked cumulative healthcare impact, even without increase in proportion hospitalized.

Development and validation of chest CT-based imaging biomarkers for early stage COVID-19 screening

Coronavirus Disease 2019 (COVID-19) is currently a global pandemic, and early screening is one of the key factors for COVID-19 control and treatment. Here, we developed and validated chest CT-based imaging biomarkers for COVID-19 patient screening from two independent hospitals with 419 patients. We identified the vasculature-like signals from CT images and found that, compared to healthy and community acquired pneumonia (CAP) patients, COVID-19 patients display a significantly higher abundance of these signals. Furthermore, unsupervised feature learning led to the discovery of clinical-relevant imaging biomarkers from the vasculature-like signals for accurate and sensitive COVID-19 screening that have been double-blindly validated in an independent hospital (sensitivity: 0.941, specificity: 0.920, AUC: 0.971, accuracy 0.931, F1 score: 0.929). Our findings could open a new avenue to assist screening of COVID-19 patients.

The psychological impact of COVID-19 outbreak on medical staff and the general public.

To assess the psychological effects of the novel coronavirus disease (COVID-19) on medical staff and the general public. During the outbreak of COVID-19, an internet-based questionnaire included The Self-rating Depression Scale (SDS), Perceived Stress Scale (PSS-10), and Impact of Event Scale-Revised (IES-R) was used to assess the impact of the pandemic situation on the mental health of medical staff and general population in Wuhan and its surrounding areas. Among the 1493 questionnaires completed, 827 (55.39%) of these were men, and 422 (28.27%) of these were medical personnel. The results suggest that the outbreak of COVID-19 has affected individuals significantly, the degree of which is related to age, sex, occupation and mental illness. There was a significant difference in PSS-10 and IES-R scores between the medical staff and the general population. The medical staff showed higher PSS-10 scores (16.813 ± 4.87) and IES-R scores (22.40 ± 12.12) compared to members of the general population PSS-10 (14.80 ± 5.60) and IES-R scores (17.89 ± 13.08). However, there was no statistically significant difference between the SDS scores of medical staff (44.52 ± 12.36) and the general public (43.08 ± 11.42). In terms of the need for psychological assistance, 50.97% of interviewees responded that they needed psychological counseling, of which medical staff accounted for 65.87% and non-medical staff accounted for 45.10%. During the ongoing COVID-19 outbreak, great attention should be paid to the mental health of the population, especially medical staff, and measures such as psychological intervention should be actively carried out for reducing the psychosocial effects.

An Automated Method of Causal Inference of the Underlying Cause of Death of Citizens.

It is of great significance to correctly infer the underlying cause of death for citizens, especially under the current worldwide situation. The medical resources of all countries are overwhelmed under the impact of coronavirus disease 2019 (COVID-19) and countries need to allocate limited resources to the most suitable place. Traditionally, the cause-of-death inference relies on manual methods, which require a large resource cost and are not so efficient. To address the challenges, in this work, we present a mixed inference method named Sink-CF. The Sink-CF algorithm is based on confidence measurement and is used to automatically infer the underlying cause of death of citizens. The method proposed in this paper combines a mathematical statistics method and a collaborative filtering and analysis algorithm in machine learning. Thus, our method can not only effectively achieve a certain accuracy, but also does not rely on a large quantity of manually labeled data to continuously optimize the model, which can save computer computing power and time, and has the characteristics of being simple, easy and efficient. The experimental results show that our method generates a reasonable precision (93.82%) and recall (90.11%) and outperforms other state-of-the-art machine learning algorithms.

PCXRNet: Pneumonia Diagnosis From Chest X-Ray Images Using Condense Attention Block and Multiconvolution Attention Block.

Coronavirus disease2019 (COVID-19)has become a global pandemic. Many recognition approaches based on convolutional neural networks have been proposed for COVID-19 chest X-ray images. However, only a few of them make good use of the potential inter- and intra-relationships of feature maps. Considering the limitation mentioned above, this paper proposes an attention-based convolutional neural network, called PCXRNet, for diagnosis of pneumonia using chest X-ray images. To utilize the information from the channels of the feature maps, we added a novel condense attention module (CDSE) that comprised of two steps: condensation step and squeeze-excitation step. Unlike traditional channel attention modules, CDSE first downsamples the feature map channel by channel to condense the information, followed by the squeeze-excitation step, in which the channel weights are calculated. To make the model pay more attention to informative spatial parts in every feature map, we proposed a multi-convolution spatial attention module (MCSA). It reduces the number of parameters and introduces more nonlinearity. The CDSE and MCSA complement each other in series to tackle the problem of redundancy in feature maps and provide useful information from and between feature maps. We used the ChestXRay2017 dataset to explore the internal structure of PCXRNet, and the proposed network was applied to COVID-19 diagnosis. As a result, the network achieves an accuracy of 94.619%, recall of 94.753%, precision of 95.286%, and F1-score of 94.996% on the COVID-19 dataset.

Immunological findings in a group of individuals who were non-responders to standard two-dose SARS-CoV-2 vaccines (preprint)

Coronavirus disease (COVID-19), caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), was declared a pandemic. The virus has infected more than 505 million people and caused more than 6 million deaths. However, data on non-responders to SARS-CoV-2 vaccines in the general population are limited. The objective of the study is to comprehensively compare the immunological characteristics of non-responders to SARS-CoV-2 vaccines in the 18-59 years with that in the 60 years and older using internationally recognized cutoff values. Participants included 627 individuals who received physical examinations and volunteered to participate in COVID-19 vaccination from the general population. The main outcome was an effective seroconversion characterized by anti-SARS-CoV-2 spike IgG level of at least 4-fold increase from baseline. Profiling of naive immune cells was analyzed prior to vaccination to demonstrate baseline immunity. Outcomes of effective seroconversion in the 18-59 years with that in the 60 years and older were compared. The quantitative level of the anti-spike IgG was significantly lower in the 60 years and older and in men among the 18-59 years. There were 7.5% of non-responders among the 18-59 years and 11.7% of non-responders in the 60 years and older using the 4-fold increase parameter. The effective seroconversion rate was significantly related to the level of certain immune cells before vaccination, such as CD4 cells, CD8 cells and B cells and the age. An individual with a titer of anti-SARS-CoV-2 spike IgG that is below 50 BAU/mL might be considered a non-responder between 14-90 days after the last vaccine dose. Booster vaccination or additional protective measures should be recommended for non-responders as soon as possible to reduce disease severity and mortality.