Extremely potent human monoclonal antibodies from COVID-19 convalescent patients.

Human monoclonal antibodies are safe, preventive, and therapeutic tools that can be rapidly developed to help restore the massive health and economic disruption caused by the coronavirus disease 2019 (COVID-19) pandemic. By single-cell sorting 4,277 SARS-CoV-2 spike protein-specific memory B cells from 14 COVID-19 survivors, 453 neutralizing antibodies were identified. The most potent neutralizing antibodies recognized the spike protein receptor-binding domain, followed in potency by antibodies that recognize the S1 domain, the spike protein trimer, and the S2 subunit. Only 1.4% of them neutralized the authentic virus with a potency of 1-10 ng/mL. The most potent monoclonal antibody, engineered to reduce the risk of antibody-dependent enhancement and prolong half-life, neutralized the authentic wild-type virus and emerging variants containing D614G, E484K, and N501Y substitutions. Prophylactic and therapeutic efficacy in the hamster model was observed at 0.25 and 4 mg/kg respectively in absence of Fc functions.

Hybrid immunity improves B cells and antibodies against SARS-CoV-2 variants.

The emergence of SARS-CoV-2 variants is jeopardizing the effectiveness of current vaccines and limiting the application of monoclonal antibody-based therapy for COVID-19 (refs. 1,2). Here we analysed the memory B cells of five naive and five convalescent people vaccinated with the BNT162b2 mRNA vaccine to investigate the nature of the B cell and antibody response at the single-cell level. Almost 6,000 cells were sorted, over 3,000 cells produced monoclonal antibodies against the spike protein and more than 400 cells neutralized the original SARS-CoV-2 virus first identified in Wuhan, China. The B.1.351 (Beta) and B.1.1.248 (Gamma) variants escaped almost 70% of these antibodies, while a much smaller portion was impacted by the B.1.1.7 (Alpha) and B.1.617.2 (Delta) variants. The overall loss of neutralization was always significantly higher in the antibodies from naive people. In part, this was due to the IGHV2-5;IGHJ4-1 germline, which was found only in people who were convalescent and generated potent and broadly neutralizing antibodies. Our data suggest that people who are seropositive following infection or primary vaccination will produce antibodies with increased potency and breadth and will be able to better control emerging SARS-CoV-2 variants.

In-label, off-label prescription, efficacy and tolerability of dalbavancin: report from a National Registry.

PURPOSE: Although dalbavancin is currently approved for the treatment of ABSSIs, several studies suggest its efficacy and tolerance as long-term therapy for other off-label indications requiring prolonged intravenous antibiotic administration. METHODS: We conducted a prospective nationwide study of dalbavancin use in real-life settings for both approved and off-label indications analysing for each case the clinical and microbiological characteristics of infection the efficacy and safety of treatments. RESULTS: During the study period (from December 2018 to July 2021), the ID specialists from 14 different centres enrolled 223 patients treated with dalbavancin [141 males (63%) and 82 females (37%); male/female ratio 1.72; mean age 59 (SD 17.2) years, (range 15-96). Most patients in the study population (136/223; 61.0%) came from community rather than health care facilities and most of them were visited in Infectious Diseases wards (93/223; 41.7%) and clinics (55/223; 24.7%) even though some patients were cured in other settings, such as surgery wards (18/223; 8.1%), orthopaedic wards (11/223; 4.9%), Emergency Rooms (7/223; 3.1%) and non-surgical other than ID wards (6/223; 2.7%). The most common ID diagnoses were osteomyelitis (44 cases/223; 19.7%; of which 29 acute and 15 chronic osteomyelitis), cellulitis (28/223; 12.5%), cutaneous abscess (23/223; 10.3%), orthopaedic prosthesis-associated infection (22/223; 9.9%), surgical site infection (20/223; 9.0%) and septic arthritis (15/223; 6.7%). CONCLUSION: In conclusion, by virtue of its PK/PD properties, dalbavancin represents a valuable option to daily in-hospital intravenous or outpatient antimicrobial regimens also for off-label indications requiring a long-term treatment of Gram-positive infections.

PRESTIGIO RING "a 59-year-old man with multidrug resistant HIV-1 infection failing a regimen including dolutegravir, rilpivirine, atazanavir/cobicistat: successful treatment tailoring based on genotypic and phenotypic resistance tests".

Management of virological failure in heavily treatment-experienced people with multidrug-resistant (MDR) HIV infection is a serious clinical challenge. New drugs with novel mechanisms of action have recently been approved, and their use has improved the outcome of subjects with limited treatment options (LTO). In this setting, the choice of antiretroviral therapy (ART) should be tailored based on the pattern of resistance, treatment history and patients' individual characteristics. While genotypic resistance testing is the reference method for analysing residual drug susceptibility, phenotypic resistance testing can provide additional support when facing LTO. Herein, we present the case of a patient with MDR HIV-1 infection on virological failure enrolled in the PRESTIGIO Registry. The salvage ART regimen, which included drugs with novel mechanisms of action (MoA), was tailored to the patient's clinical characteristics and on the resistance pattern explored with genotypic and phenotypic investigation, allowing the achievement of viro-immunological success. The use of recently approved drugs with novel MoA, combined with an optimized background regimen, may also achieve virological suppression in people with LTO.

Immune checkpoint analysis of T-cell responses to pp65 and IE-1 antigens in end-stage lung diseases.

Lung transplant (LTX) patients are at high risk of cytomegalovirus (CMV) infection, which is often associated with high mortality and morbidity. Reactivation of CMV causes cell injury due to the cytopathic effect of viral replication and triggering of T cell immunity. The aim of this study was to compare expression of immune checkpoints (ICs) (PD-1, CTLA-4, LAG-3 and TIGIT) in CD4, CD8 and CD56 and activation markers CD137, CD154 and CD69 of end-stage patients awaiting lung transplant. Eighteen pre-LTX positive for anti-CMV IgG titres and 18 healthy subjects were enrolled. IC and activation markers have been evaluated through flow cytometric analysis in HC and pre-LTX patients. Reactive (QF+) and unreactive (QF-) patients were stratified according to QuantiFERON-CMV assays. ICs' and activation markers' expression were determined before and after in vitro stimulation with pp-65 and IE-1 antigens. Lower expression of PD-1 was observed in CD4 and CD8 cells of pre-LTX patients than controls, whereas CTLA4 appeared upregulated in CD56 and CD8 cells. TIGIT is increased on the surface of CD4, CD8 and NK cells after peptide stimulation in QF-negative patients and PD-1 is only downregulated after stimulation in the QF-positive patients. This study provides new evidence of immune dysregulation in patients with end-stage lung disorders, particularly in relation to immune checkpoint cell biology. The change in QF+ mostly happens on cytotoxic cells NK and CD8, while the changes in QF- were observed in adaptive immune cells, including CD4 and CD8.

Cytomegalovirus Infection Is Associated with Development of Chronic Lung Allograft Dysfunction.

BACKGROUND: Cytomegalovirus (CMV) is the major and most common opportunistic infection complicating lung transplant (LTX). The aim of this study was to analyse the epidemiological aspects of CMV infection in lung transplant patients subject to a pre-emptive anti-CMV approach and to study the impact of this infection on lung transplant outcome, in terms of onset of chronic lung allograft dysfunction (CLAD). METHODS: This single-centre retrospective study enrolled 87 LTX patients (median age 55.81 years; 41 females, 23 single LTX, 64 bilateral LTX). All patients were managed with a pre-emptive anti-CMV approach. The incidences of the first episode of CMV infection, 1, 3, 6 and 12 months after LTX, were 12.64%, 44.26%, 50.77% and 56.14%. A median interval of 41 days elapsed between LTX and the first episode of CMV infection. The median blood load of CMV-DNA at diagnosis was 20,385 cp/ml; in 67.64% of cases, it was also the peak value. Patients who had at least one episode had shorter CLAD-free survival. Patients who had three or more episodes of CMV infection had the worst outcome. RESULTS: CMV infection was confirmed to be a common event in lung transplant patients, particularly in the first three months after transplant. It had a negative impact on transplant outcome, being a major risk factor for CLAD. The hypothesis that lower viral replication thresholds may increase the risk of CLAD is interesting and deserves further investigation.

Monitoring Anti-PEG Antibodies Level upon Repeated Lipid Nanoparticle-Based COVID-19 Vaccine Administration.

PEGylated lipids are one of the four constituents of lipid nanoparticle mRNA COVID-19 vaccines. Therefore, various concerns have been raised on the generation of anti-PEG antibodies and their potential role in inducing hypersensitivity reactions following vaccination or in reducing vaccine efficacy due to anti-carrier immunity. Here, we assess the prevalence of anti-PEG antibodies, in a cohort of vaccinated individuals, and give an overview of their time evolution after repeated vaccine administrations. Results indicate that, in our cohort, the presence of PEG in the formulation did not influence the level of anti-Spike antibodies generated upon vaccination and was not related to any reported, serious adverse effects. The time-course analysis of anti-PEG IgG showed no significant booster effect after each dose, whereas for IgM a significant increase in antibody levels was detected after the first and third dose. Data suggest that the presence of PEG in the formulation does not affect safety or efficacy of lipid-nanoparticle-based COVID-19 vaccines.

Efficacy and durability of two- vs. three-drug integrase inhibitor-based regimens in virologically suppressed HIV-infected patients: Data from real-life ODOACRE cohort.

OBJECTIVES: The aim of the present study was to compare the efficacy and durability of treatment switch to two-drug (2DR) vs. three-drug (3DR) integrase inhibitor (InSTI)-based regimens in a real-life setting. METHODS: Within the ODOACRE cohort, we selected adult patients with HIV RNA < 50 copies/mL switching to an InSTI-based 2DR or 3DR. Survival analyses were performed to estimate the probability of virological failure (VF, defined as one HIV RNA > 1000 copies/mL or two consecutive HIV RNA > 50 copies/mL) and treatment discontinuation (TD, defined as any modification, intensification or interruption of the regimen), and to evaluate their predictors. RESULTS: Overall, 1666 patients were included, of whom 1334 (80%) were treated with a 3DR (19.9%, 25.0% and 55.1% elvitegravir-, raltegravir- and dolutegravir-based, respectively) and 332 (20%) with a 2DR (79.2% dolutegravir + lamivudine and 20.8% dolutegravir + rilpivirine). Over a median (interquartile range) follow-up of 100 (52-150) weeks, 52 (3.1%) patients experienced VF with an incidence of 1.5/100 person-year of follow-up (PYFU). The estimated 96-week probability of VF was similar for the 2DR and 3DR groups (2.3% vs. 2.8%, P = 0.53), but it was higher for elvitegravir (4.9%) and raltegravir (5.0%) than for dolutegravir (1.5%) (P = 0.04). Four hundred (24%) patients discontinued their InSTI-based regimen, with an incidence of 11.3/100 PYFU. At 96 weeks, 3DRs showed a higher probability of TD for any reason (20.6% vs. 11.2%, P < 0.001) and TD for toxicity (9.0% vs. 6.6%, P = 0.02) when compared with 2DRs. A higher risk of TD for central nervous system toxicity was observed for dolutegravir than for elvitegravir and raltegravir (4.0% vs. 2.5% vs. 0.6%, P = 0.005). CONCLUSIONS: In virologically suppressed HIV-infected patients, 2DRs showed an efficacy similar to 3DRs but with better tolerability.

The impact of DAA-mediated HCV eradication on CD4+ and CD8+ T lymphocyte trajectories in HIV/HCV coinfected patients: Data from the ICONA Foundation Cohort.

HCV infection has been hypothesized as a contributor of poor CD4+ recovery in patients living with HIV (PLWHIV). Aim of this study was to evaluate CD4+ , CD8+ cells and CD4/CD8 ratio trends before and after HCV treatment with direct acting agents (DAA) in PLWHIV. HIV/HCV patients enrolled in ICONA and HepaICONA cohorts with HIV-RNA≤50 copies/ml who achieved a sustained viral response after DAA treatment were studied. A linear regression model was used to investigate CD4+ , CD8+ and CD4/CD8 changes 12 months before and after DAA treatment. A total of 939 HIV/HCV patients were included, 225 (24.0%) female, median age: 53 years (IQR 50-56). At DAA initiation, CD4+ T cell count was <350 cells/mm3 in 164 patients (17.5%), and 246 patients (26.2%) had liver stiffness>12.5 kPa. Trends of CD4+ and CD4/CD8 ratio were similar before and after DAA in all study populations (CD4+ change +17.6 cells/mm3 (95%CI -33.5; 69.4, p = 0.494); CD4/CD8 change 0.013 (95%CI -0.061; 0.036, p = 0.611). However, patients treated with ribavirin (RBV)-free DAA showed a significant decrease in CD8+ cells (-204.3 cells/mm3 , 95%CI -375.0;-33.4, p = 0.019), while patients treated with RBV experienced CD8+ cell increase (+141.2 cells/mm3 , 95%CI 40.3; 242.1, p = 0.006). In conclusion, HCV eradication following DAA treatment does not seem to have an impact on CD4+ T cell recovery in PLWHIV. However, a fast decline of CD8+ T cells has been observed in patients treated without RBV, suggesting a favourable effect of HCV clearance on the general state of immune activation.

Serum KL-6 concentrations as a novel biomarker of severe COVID-19.

Severe acute respiratory syndrome coronavirus 2-induced direct cytopathic effects against type I and II pneumocytes mediate lung damage. Krebs von den Lungen-6 (KL-6) is mainly produced by damaged or regenerating alveolar type II pneumocytes. This preliminary study analyzed serum concentrations of KL-6 in patients with coronavirus disease (COVID-19) to verify its potential as a prognostic biomarker of severity. Twenty-two patients (median age [interquartile range] 63 [59-68] years, 16 males) with COVID-19 were enrolled prospectively. Patients were divided into mild-moderate and severe groups, according to respiratory impairment and clinical management. KL-6 serum concentrations and lymphocyte subset were obtained. Peripheral natural killer (NK) cells/µL were significantly higher in nonsevere patients than in the severe group (P = .0449) and the best cut-off value was 119 cells/µL. KL-6 serum concentrations were significantly higher in severe patients than the nonsevere group (P = .0118). Receiver operating characteristic analysis distinguished severe and nonsevere patients according to KL-6 serum levels and the best cut-off value was 406.5 U/mL. NK cell analysis and assay of KL-6 in serum can help identify severe COVID-19 patients. Increased KL-6 serum concentrations were observed in patients with severe pulmonary involvement, revealing a prognostic value and supporting the potential usefulness of KL-6 measurement to evaluate COVID-19 patients' prognosis.

Efficacy and tolerability of lamivudine plus dolutegravir compared with lamivudine plus boosted PIs in HIV-1 positive individuals with virologic suppression: a retrospective study from the clinical practice.

BACKGROUND: Direct comparisons between lamivudine plus bPIs and lamivudine plus dolutegravir as maintenance strategies in virologically-suppressed HIV positive patients are lacking. METHODS: Time to treatment discontinuation (TD) and virological failure (VF) were compared in a cohort of HIV+ patients on a virologically-effective ART starting lamivudine with either darunavir/r, atazanavir/r or dolutegravir. Changes in laboratory parameters were also evaluated. RESULTS: Four-hundred-ninety-four patients were analyzed (170 switching to darunavir/r, 141 to atazanavir/r, 183 to dolutegravir): median age was 49 years, with 8 years since ART start. Groups differed for age, HIV-risk factor, time since HIV-diagnosis and on ART, previous therapy and reasons for switching. Estimated proportions free from TD at week 48 and 96 were 79.8 and 48.3% of patients with darunavir/r, 87.0 and 70.9% with atazanavir/r, and 88.2 and 82.6% with dolutegravir, respectively (p < 0.001). Calendar years, HIV-risk factor, higher baseline cholesterol and an InSTI-based previous regimen predicted TD, whereas lamivudine+dolutegravir therapy and previous tenofovir use were protective. VF was the cause of TD in 6/123 cases with darunavir/r, 4/97 with atazanavir/r and 3/21 with dolutegravir. Other main reasons for TD were: toxicity (43.1% with darunavir/r, 39.2% with atazanavir/r, 52.4% with dolutegravir), further simplification (36.6% with darunavir/r, 30.9% with atazanavir/r, 14.3% with dolutegravir). Incidence of VF did not differ among study groups (p = 0.747). No factor could predict VF. Lipid profile improved in the dolutegravir group, whereas renal function improved in the bPIs groups. CONCLUSIONS: In real practice, a switch to lamivudine+dolutegravir showed similar efficacy but longer durability than a switch to lamivudine+bPIs.

Nasopharingeal bacterial and fungal colonization in HIV-positive versus HIV-negative adults.

OBJECTIVES: To compare mucosal flora in HIV-positive and HIV-negative subjects, to assess chemosusceptibility patterns of carriage isolates and to evaluate possible predisposing factors within the two groups. METHODS: We analyzed microbes isolated from nasopharyngeal swabs in virologically suppressed and immunologically stable HIV-positive adult outpatients (n=105) at baseline and after 12 months and in an age-matched cohort of HIV-negative outpatients (n=100) at baseline. Bacteria and Candida spp strains were isolated and identified through standard biochemical assays and chemosusceptibility tests were performed. Multi Locus Sequence Typing was also determined to characterize Staphylococcus aureus isolates from HIV-infected persistent carriers. RESULTS: In HIV-positive patients a significantly higher rate of colonization by S. aureus as compared to HIV-negative controls was observed (19% vs 8%, p=0.02), with a relevant percentage of penicillin resistant strains (15% vs 0, p=0.24). Methicillin resistant strains were recovered only from HIV-positive subjects. Overall HIV-positive status was the only predictor of S. aureus colonization (OR 2.77, 95% CI 1.03;7.41, p=0.04). CONCLUSIONS: The nasopharyngeal bacterial flora differs between HIV-positive and HIV-negative subjects and appears relevant for possible development of staphylococcal infections in HIV-positive patients.

Non-granulomatous cerebellar infection by Acanthamoeba spp. in an immunocompetent host.

Acanthamoeba spp. is a free-living amoeba, frequently involved in keratitis by contact lens in immunocompetent hosts. Anecdotal reports associate Acanthamoeba spp. as a cause of severe granulomatous encephalitis in immunocompromised and, less frequently, in immunocompetent subjects. Data regarding clinical and therapeutic management are scanty and no defined therapeutic guidelines are available. We describe an unusual case of non-granulomatous Acanthamoeba cerebellitis in an immunocompetent adult male, with abrupt onset of neurological impairment, subtle hemorrhagic infarction at magnetic resonance imaging, and initial suspicion of cerebellar neoplasm. Histopathological findings of excised cerebellar mass revealed the presence of necrosis and inflammation with structure resembling amoebic trophozoites, but without granulomas. Polymerase chain reaction from cerebellar tissue was positive for Acanthamoeba T4 genotype. Due to gastrointestinal intolerance to miltefosine, the patient was treated with long-term course of fluconazole and trimethoprim/sulphamethoxazole, obtaining complete clinical and neuroradiological resolution.

Laboratory diagnosis of Mycoplasma pneumoniae infections: data analysis from clinical practice.

An etiological diagnosis of respiratory infections caused by Mycoplasma pneumoniae is particularly challenging due to the lack of a definite standard test. This study aimed to analyse the correlation and combination of diagnostic results obtained from direct and indirect assays (Mycoplasma pneumoniae DNA by PCR and serology) in use at a first level diagnostic laboratory. Samples from patients with respiratory infections tested for M. pneumoniae during routine clinical practice were retrospectively analysed. In pediatric patients <15 years old, we documented a significantly higher proportion of IgM positive results (23.6% versus 3.9% in ≥15-year-old patients, p<0.0001) but a lower IgM specificity (false positive IgM 34.8% versus 12.2% in ≥15 years old patients, p 0.01), as verified by seroconversion. A small percentage (4%) of respiratory samples were positive for M. pneumoniae DNA regardless of age and type of sample. Assuming IgM positivity as the reference standard, PCR showed a total lack of sensitivity in patients <15 years old and 20% sensitivity in children <15 years old; specificity was 95% in both age groups. Agreement between PCR and IgM serology was slight (Cohen's kappa 0.09). According to our data, no single diagnostic test could be considered optimal for M. pneumoniae detection and improved assays are required.

Staphylococcus aureus vaccine preclinical and clinical development: current state of the art.

Staphylococcus aureus is a major pathogen in both community and hospital settings. It is a significant etiological agent to treat in healthcare-related infections due to both its ability to cause invasive infection as well as to form biofilm on biomaterials and the high prevalence of resistance to first line antibiotics. The most challenging preventive strategy is vaccine development to guarantee a full and durable protection from staphylococcal diseases in all different high-risk populations, even if the lack of a known correlate of protection from S. aureus is a major hindrance to this effort. We aimed to review the most recent advances in the field of vaccinology against S. aureus, highlighting the potential for future application of the different experimental vaccine types. Several vaccines have completed their preclinical phase of development and others have been tested in humans, however no successful phase III clinical trial has yet been completed.

Distribution of different HBV DNA forms in plasma and peripheral blood mononuclear cells (PBMCs) of chronically infected patients with low or undetectable HBV plasma viremia.

Few studies have documented hepatitis B virus (HBV) DNA in peripheral blood mononuclear cells (PBMCs). We developed real-time PCR methods for differential amplification of covalently closed circular (cccDNA) and total HBV DNA (tDNA). The different distribution of cccDNA and tDNA in plasma and PBMCs was evaluated in 37 patients with low or undetectable viremia. Plasma tDNA measured by the Abbott reference system and the in-house assay correlated well (Spearman rho = 0.804; P<0.0001). tDNA was detected in four PBMC samples, all from patients with detectable plasma viremia (range 633-6,406 IU/ml), cccDNA was not detected in any sample. The reasons for apparently discrepant results need further investigation but possibly include the high diversification of HBV status and plasma viremia levels.

Evaluation and Optimization of an ELISA Procedure to Quantify Antibodies Against Pneumococcal Polysaccharides Included in the 13-Valent Conjugate Vaccine.

The 13-valent pneumococcal conjugate vaccine (PCV-13) is recommended for HIV-infected people, although its effectiveness in this population remains under evaluation. In this study, we describe the development, optimization, and analytical validation of an ELISA procedure to measure specific antibodies for the pneumococcal polysaccharide serotypes included in PCV13 vaccine, testing sera obtained from HIV-infected outpatients (n = 30) who received the vaccine. The protocol followed the last version of WHO guidelines, based on the new standard 007sp, with the modification of employing Statens Serum Institut (SSI) antigens. We supplied the assay performance validation in terms of sensitivity, reproducibility, precision and accuracy. In addition we detailed optimal antigen-coating concentrations and ELISA conditions common to all 13 serotypes, suitable for laboratories performing these assays in order to standardize the method. Our procedure showed reproducibility and reliability, making it a valid alternative for evaluating the response to pneumococcal serotypes included in PCV13 vaccine.

First report of spondylodiscitis due to vancomycin heteroresistant Staphylococcus capitis in immunocompetent host.

We report a successfully treated case of spondylodiscitis and bloodstream infection due to vancomycin heteroresistant Staphylococcus capitis, in an adult immunocompetent patient with multiple antibiotics intolerance. S. capitis is rarely involved in osteomyelitis and, to our knowledge, this is the first report of vancomycin heteroresistance phenomenon in an S. capitis strain causing spondylodiscitis.

Spike-Specific Memory B Cell Response in Hematopoietic Cell Transplantation Recipients following Multiple mRNA-1273 Vaccinations: A Longitudinal Observational Study.

Preventing SARS-CoV-2 infection is of utmost importance in allogeneic hematopoietic cell transplantation patients (allo-HCT), given their heightened susceptibility to adverse outcomes associated with SARS-CoV-2 infection. However, limited data are available regarding the immune response to COVID-19 vaccines in these subjects, particularly concerning the generation and persistence of spike-specific memory response. Here, we analyzed the spike-specific memory B cells in a cohort of allo-HCT recipients vaccinated with multiple doses of the mRNA-1273 vaccine and monitored the spike-specific antibody response from baseline up to one month after the fourth dose. After the primary vaccine series, the frequency of spike-specific B cells, detected within the pool of Ig-switched CD19+ cells, significantly increased. The booster dose further induced a significant expansion, reaching up to 0.28% of spike-specific B cells. The kinetics of this expansion were slower in the allo-HCT recipients compared to healthy controls. Spike-specific IgG and ACE2/RBD binding inhibition activity were observed in 80% of the allo-HCT recipients after the first two doses, with a significant increase after the third and fourth booster doses, including in the subjects who did not respond to the primary vaccine series. Additionally, 87% of the allo-HCT recipients exhibited positive cross-inhibition activity against the BA.1 variant. Our findings provide evidence that allo-HCT recipients need repeated doses of the mRNA-1273 vaccine to induceSARS-CoV-2 specific immune response similar to that observed in healthy individuals. This is particularly crucial for vulnerable individuals who may exhibit a limited response to the primary series of SARS-CoV-2 vaccination.

Homologous or heterologous administration of mRNA or adenovirus-vectored vaccines show comparable immunogenicity and effectiveness against the SARS-CoV-2 Omicron variant.

BACKGROUND: Heterologous prime-boost schedules have been employed in SARS-CoV-2 vaccination, yet additional data on immunogenicity and effectiveness are still needed. RESEARCH DESIGN AND METHODS: Here, we measured the immunogenicity and effectiveness in the real-world setting of the mRNA booster dose in 181 subjects who had completed primary vaccination with ChAdOx1, BNT162b2, or mRNA1273 vaccines (IMMUNO_COV study; protocol code 18,869). The spike-specific antibody and B cell responses were analyzed up to 6 months after boosting. RESULTS: After an initial slower antibody response, the heterologous ChAdOx1/mRNA prime-boost formulation elicited spike-specific IgG titers comparable to homologous approaches, while spike-specific B cells showed a higher percentage of CD21-CD27- atypical cells compared to homologous mRNA vaccination. Mixed combinations of BNT162b2 and mRNA-1273 elicited an immune response comparable with homologous strategies. Non-significant differences in the Relative Risk of infection, calculated over a period of 18 months after boosting, were reported among homologous or heterologous vaccination groups, indicating a comparable relative vaccine effectiveness. CONCLUSIONS: Our data endorse the heterologous booster vaccination with mRNA as a valuable alternative to homologous schedules. This approach can serve as a solution in instances of formulation shortages and contribute to enhancing vaccine strategies for potential epidemics or pandemics.