Prolonged Omicron-Specific B Cell Maturation Alleviates Immune Imprinting Induced by SARS-CoV-2 Inactivated Vaccine.

SARS-CoV-2 ancestral strain-induced immune imprinting poses great challenges to updating vaccines for new variants. Studies showed that repeated Omicron exposures could override immune imprinting induced by inactivated vaccines but not mRNA vaccines, a disparity yet to be understood. Here, we analyzed the immune imprinting alleviation in inactivated vaccine (CoronaVac) cohorts after a long-term period following breakthrough infections (BTI). We observed in CoronaVac-vaccinated individuals who experienced BA.5/BF.7 BTI, the proportion of Omicron-specific memory B cells (MBCs) substantially increased after an extended period post-Omicron BTI, with their antibodies displaying enhanced somatic hypermutation and neutralizing potency. Consequently, the neutralizing antibody epitope distribution encoded by MBCs post-BA.5/BF.7 BTI after prolonged maturation closely mirrors that in BA.5/BF.7-infected unvaccinated individuals. Together, these results indicate the activation and expansion of Omicron-specific naïve B cells generated by first-time Omicron exposure helped to alleviate CoronaVac-induced immune imprinting, and the absence of this process should have caused the persistent immune imprinting seen in mRNA vaccine recipients.

COVID-19 Disease Incidence and Severity in Previously Infected Unvaccinated Compared with Previously Uninfected Vaccinated Persons.

Using the VA COVID-19 National Database, we created matched pairs of previously uninfected vaccinated (≥2 doses of an mRNA vaccine) and previously infected unvaccinated individuals. The incidence rate (per 1000 person-days) of breakthrough infection among vaccinated individuals (0.30, 95% CI 0.29-0.32) was similar to reinfection rate among unvaccinated individuals (0.31, 95% CI 0.30-0.32; p=0.5). The incidence rate of hospitalization/death was higher after reinfection (7.31, 95% CI 6.66-8.03) compared with rate after breakthrough infection (4.69, 95% CI 4.06-5.42; P<0.0001). Conclusion: The incidence of hospitalization/death is significantly higher after reinfection among unvaccinated individuals compared with breakthrough infection after vaccination.

Aging brought additional immune response alterations after breakthrough infections with the Omicron BA.5/BF.7 variants: Protein immune mechanism.

The global spread of the Omicron variant strain BA.5/BF.7 has led to an increase in breakthrough infections. The elderly population shows different immune responses after infection due to the aging of the immune system, which has not been fully studied. The aim of this study was to investigate the effect of aging on immune response after breakthrough infection of Omicron BA.5/BF.7 variant, especially the changes of protein immune mechanism. The study analyzed the concentration of antibodies in serum and their ability to neutralize the mutant strain by comparing the immune response of the elderly population and the young population after infection. Proteomics techniques were used to assess differences in the expression of key proteins in immune cells of different age groups. The study found that older subjects produced lower levels of antibodies after infection than younger subjects and showed a significantly reduced ability to neutralize against BA.5/BF.7. In addition, proteomic analysis showed that the expression of proteins related to inflammation and apoptosis significantly increased in the immune cells of the elderly, while the proteins related to antiviral response and cell repair significantly decreased. These findings provide new ideas for immune intervention strategies in the elderly population, and emphasize the targeted research of anti-virus vaccines.

Longevity of hybrid immunity against SARS-CoV-2 in adults vaccinated with an adenovirus-based COVID-19 vaccine.

BACKGROUND: Hybrid immunity provides better protection against COVID-19 than vaccination or prior natural infection alone. It induces high magnitude and broadly cross-reactive neutralising anti-Spike IgG antibodies. However, it is not clear how long these potent antibodies last, especially in the context of adenovirus-based COVID-19 vaccines. METHODS: We conducted a longitudinal cohort study and enrolled 20 adults who had received an adenovirus-based COVID-19 vaccine before a laboratory-confirmed SARS-CoV-2 infection. We followed up the study participants for 390 days post the initial breakthrough infection. We assessed the longevity and cross-reactive breadth of serum antibodies against SARS-CoV-2 variants of concern (VOCs), including Omicron. RESULTS: The binding anti-Spike IgG antibodies remained within the reported putative levels for at least 360 days and were cross-neutralising against Beta, Gamma, Delta, and Omicron. During the follow up period, a median of one SARS-CoV-2 re-infection event was observed across the cohort, but none resulted in severe COVID-19. Moreover, the re-exposure events were associated with augmented anti-Spike and anti-RBD IgG antibody titres. CONCLUSIONS: This study confirms that hybrid immunity provides durable broadly cross-reactive antibody immunity against SARS-CoV-2 variants of concern for at least a year (360 days), and that it is further augment by SARS-CoV-2 re-exposure.

First Case of HIV Seroconversion With Integrase Resistance Mutations on Long-Acting Cabotegravir for Prevention in Routine Care.

Background: Long-acting cabotegravir (CAB-LA) is highly effective for HIV prevention, but delayed HIV diagnoses and integrase strand transfer inhibitor (INSTI) resistance were observed in trials. We report the first case in routine clinical care of HIV infection on CAB-LA with INSTI resistance. Methods: The SeroPrEP study enrolls individuals in the United States who acquire HIV on pre-exposure prophylaxis modalities to assess diagnostics, antiretroviral (ARV) drug levels, resistance, and treatment outcomes. Resistance mutations in full-length HIV-1 integrase were identified by single-genome sequencing (SGS). Cabotegravir concentrations in plasma and hair segments were measured by liquid chromatography-tandem mass spectrometry. Results: A 23-year-old gender-nonbinary person, male at birth, restarted CAB-LA 6 months after discontinuation due to losing insurance. Prior to restart, HIV-1 RNA was not detected, but 20 days elapsed before CAB-LA injection. After the second CAB-LA injection, HIV antigen/antibody returned reactive (HIV-1 RNA 451 copies/mL). SGS of plasma HIV-1 RNA identified INSTI mutation Q148R in 2/24 sequences 2 days postdiagnosis; commercial genotype failed amplification. Cabotegravir hair concentration was 0.190 ng/mg 2 weeks prediagnosis; plasma cabotegravir was high (3.37 µg/mL; ∼20× PA-IC90) 14 days postdiagnosis. Viral suppression was maintained for 6 months on darunavir/cobicistat/emtricitabine/tenofovir alafenamide, then switched to doravirine + emtricitabine/tenofovir alafenamide due to nausea. Conclusions: In this first case of HIV infection on CAB-LA with INSTI resistance in routine care, cabotegravir resistance was detected only with a sensitive research assay. Accelerated pathways to minimize time between HIV testing and CAB-LA initiation are needed to optimize acute HIV detection and mitigate resistance risk. Sustained product access regardless of insurance is imperative to reduce HIV infections on CAB-LA.

SARS-COV-2 breakthrough infection and its covariates among healthcare providers of a hospital in Bangladesh during the omicron wave.

Introduction: Breakthrough infection by SARS-COV-2 virus among vaccinated individuals has been reported from all over the world and it has created a substantial challenge in designing strategies to live with the virus in the post-pandemic era. Factors affecting the extent and nature of breakthrough infection are still not fully understood and those are known to vary depending on host and agent factors. Health Care Workers (HCWs), especially in hospital settings, are front-liners in combating the epidemic and, consequently, they are more vulnerable to breakthrough infection by SARS-COV-2. Like most of the countries of the world, Bangladesh went through several waves of COVID-19 and the last (3rd wave) was the widespread Omicron wave during the winter of 2022. HCWs in Bangladesh have been disproportionately affected by the virus. Under this context, the aim of the present study was to explore breakthrough infection (BTI) and its host-related covariates among HCWs of a COVID-dedicated city-based hospital during the Omicron wave in Bangladesh. Materials and methods: An observational cross-sectional study was conducted on 267 HCWs of the Narayanganj Tertiary (300-bed) hospital during February-March 2022 which coincided with the terminal part of the 3rd wave. Data were collected by trained Field Assistants using Interviewer-administered Data Collection Forms with Questionnaires as instruments. Previous COVID-19 status (any time after the onset of the pandemic and within last 3 months) was explored by the history of specific symptoms as well as by the confirmatory rtPCR test reports from DGHS approved laboratories Anti-nucleocapsid antibody (Anti-N-Ab) in venous blood samples, assayed by a chemiluminescent ELISA technique, was used as a seroprevalence-based marker of breakthrough infection during the preceding few months. Data were analyzed by bivariate as well as multivariate statistics using the IBM-SPSS software. Results: The median age (range) of the HCWs was 38 (21-65) years; Body Mass Index (BMI, kg/m2) 25 (15-49); and Waist-Hip Ratio (WHR) was 0.92 (0.46-1.21). The male subjects had significantly higher median age (p = 0.01) and higher WHR (p = 0.001) as compared to the female subjects. As per the BMI category, subjects with overweight and obesity constituted 83.3 % of the male subjects as compared to 61.6 % of the female subjects (p = 0.001). The time lapse between receiving of 3rd dose and blood sampling was significantly higher among females compared to males (median days 60 vs 49, p < 0.02) indicating earlier vaccination with 1st booster dose among females. A proportion of 51.85 % male and 49.68 % female subjects showed Anti-N-Ab positivity; there was no significant difference between the gender groups. Also, there was no significant difference among male and female subjects regarding the Ab levels. On Spearman correlation analysis, a tendency of association of WHR with Ab level was observed among the male subjects; however, the association did not show statistical significance (p = 0.09). On binary logistic regression Ab positivity was found to be independently associated with WHR (p = 0.03), and prior SARS-COV-2 infection within the last 3 months (p = 0.02) among males. When all the subjects were considered together, COVID symptom positivity during the last 3 months (p = 0.067) and receiving the 1st booster dose (p = 0.07) showed a tendency of association with Ab positivity. On multiple regression analysis, Ab levels showed a negative association with WHR (p = 0.035) among males. Conclusions: More than 50 % of the vaccinated hospital-based HCWs in Bangladesh suffered from BTI during the winter of 2022 when the Omicron wave (the 3rd wave) of COVID-19 was at its peak. The data also indicate that overweight and obesity are major host-related risk factors underlying BTI. Inadequate coverage by a booster dose seems to be another determinant of BTI and the level of immune response in this population.

COVID-19 breakthrough infections in vaccinated individuals at BPKIHS, Nepal.

BACKGROUND: Although there have been reports of COVID-19 breakthrough infections in vaccinated individuals, the vaccines have demonstrated a high efficacy in preventing severe illness and death. Nepal has reported fewer studies of COVID-19 breakthrough infections. Hence, this study has objective to assess the prevalence, and to describe clinical characteristics of severe acute respiratory syndrome coronavirus 2 (SARS-CoV2) breakthrough infection. METHODS: This descriptive study was conducted from January to December 2022. The study enrolled 200 individuals who had received the recommended doses of the COVID-19 vaccine and they were RT-PCR positive diagnosed with vaccine breakthrough infections after 14 days of completing the vaccination course. The patient's demographic and clinical profiles, as well as their outcomes in terms of severity, length of hospital stay, and mortality were recorded. RESULTS: The prevalence of SARS-CoV2 infection was 6.3% (547/8682). Among fully vaccinated personnel, the prevalence of breakthrough infections was 6.2% (200/3175). This study found the Omicron variants in respondents. The mean age of the patients was 38.28 years, and 41.5% (83/200) of the breakthrough cases were healthcare workers. The mean time gap between the second dose of vaccination and a positive RT-PCR test was 354.68 days. Of the 200 breakthrough cases, 89% (178) had mild symptoms, 9% (17) had moderate symptoms requiring hospitalization, and 2% (4) were severe cases that required intensive care facility. Among the severe cases, 3 out 4 were above 60 years old. Furthermore, the patients greater than 60 years had longer hospital stays (p < 0.0001) however no deaths were recorded. CONCLUSION: Fully vaccinated individuals can experience COVID-19 breakthrough infections and the majority of cases present with mild symptoms. Elderly patients have a higher likelihood of severe disease and longer hospital stay compared to younger patients. The results of this study emphasize the importance of vaccination in mitigating the severity of the disease.

Humoral and cellular immune response from first to fourth SARS-CoV-2 mRNA vaccination in anti-CD20-treated multiple sclerosis patients-a longitudinal cohort study.

Background: This study examines the humoral and cellular response in multiple sclerosis (MS) patients on anti-CD20 therapy before and after the 1st to 4th BNT162b2 mRNA SARS-CoV-2 vaccination and the relationship with breakthrough infection. Methods: Participants with McDonald 2017 MS that were treated with ocrelizumab were included. The study duration was throughout the COVID-19 pandemic until four months after fourth mRNA SARS-CoV-2 vaccination (BNT162b2). Longitudinal blood samples were analysed for: IgG antibodies of SARS-CoV-2 spike anti-receptor binding domain (anti-RBD), nucleocapsid IgG antibodies (anti-N) and activation induced marker expressing CD4+, CD8+ T-cells and concentration of ocrelizumab and anti-drug antibodies. Incidences of breakthrough infection were confirmed with SARS-CoV-2 PCR tests. Results: The rate of anti-RBD positive participants increased substantially between the third and fourth vaccination from 22.2% to 55.9% (median 54.7 BAU/mL; IQR: 14.5 - 221.2 BAU/mL and 607.7 BAU/mL; IQR: 29.4 - 784.6 BAU/mL, respectively). Within the same period 75% of participants experienced breakthrough infection. The fourth vaccination resulted in an additional increase in seropositive individuals (64.3%) (median 541.8 BAU/mL (IQR: 19.1-1007 BAU/mL). Breakthrough infection did not influence the cellular response without a significant change after the fourth vaccination. During the study period two participants had detectable anti-N, both after the fourth vaccination. No correlation was found between serum concentration of ocrelizumab and the humoral and cellular response. Discussion: Low levels or absence of specific anti-RBD following vaccination, with a significant increase after breakthrough infections and boosted by the fourth vaccination. T-cell reactivity remained sustained and unaffected by breakthrough infections.

Ultrapotent class I neutralizing antibodies post Omicron breakthrough infection overcome broad SARS-CoV-2 escape variants.

BACKGROUND: The spread of emerging SARS-CoV-2 immune escape sublineages, especially JN.1 and KP.2, has resulted in new waves of COVID-19 globally. The evolving memory B cell responses elicited by the parental Omicron variants to subvariants with substantial antigenic drift remain incompletely investigated. METHODS: Using the single B cell antibody cloning technology, we isolated single memory B cells, delineated the B cell receptor repertoire and conducted the pseudovirus-based assay for recovered neutralizing antibodies (NAb) screening. We analyzed the cryo-EM structures of top broadly NAbs (bnAbs) and evaluated their in vivo efficacy (golden Syrian hamster model). FINDINGS: By investigating the evolution of human B cell immunity, we discovered a new panel of bnAbs arising from vaccinees after Omicron BA.2/BA.5 breakthrough infections. Two lead bnAbs neutralized major Omicron subvariants including JN.1 and KP.2 with IC50 values less than 10 ng/mL, representing ultrapotent receptor binding domain (RBD)-specific class I bnAbs. They belonged to the IGHV3-53/3-66 clonotypes instead of evolving from the pre-existing vaccine-induced IGHV1-58/IGKV3-20 bnAb ZCB11. Despite sequence diversity, they targeted previously unrecognized, highly conserved conformational epitopes in the receptor binding motif (RBM) for ultrapotent ACE2 blockade. The lead bnAb ZCP3B4 not only protected the lungs of hamsters intranasally challenged with BA.5.2, BQ.1.1 and XBB.1.5 but also prevented their contact transmission. INTERPRETATION: Our findings demonstrated that class I bnAbs have evolved an ultrapotent mode of action protecting against highly transmissible and broad Omicron escape variants, and their epitopes are potential targets for novel bnAbs and vaccine development. FUNDING: A full list of funding bodies that contributed to this study can be found in the Acknowledgements section.

Anti-RBD Antibody Levels and IFN-γ-Specific T Cell Response Are Associated with a More Rapid Swab Reversion in Patients with Multiple Sclerosis after the Booster Dose of COVID-19 Vaccination.

This study investigated the incidence and severity of SARS-CoV-2 breakthrough infections (BIs) and the time to swab reversion in patients with multiple sclerosis (PwMS) after the booster dose of COVID-19 mRNA vaccines. We enrolled 64 PwMS who had completed the three-dose mRNA vaccine schedule and had never experienced COVID-19 before. Among the 64 PwMS, 43.8% had BIs with a median time since the third vaccine dose of 155 days. BIs occurred more frequently in ocrelizumab-treated patients (64.7%). Patients with a relapsing-remitting MS course showed a reduced incidence of BIs compared with those with a primary-progressive disease (p = 0.002). Having anti-receptor-binding domain (RBD) antibodies represented a protective factor reducing the incidence of BIs by 60% (p = 0.042). The majority of BIs were mild, and the only severe COVID-19 cases were reported in patients with a high Expanded Disability Status Scale score (EDSS > 6). The median time for a negative swab was 11 days. Notably, fingolimod-treated patients take longer for a swab-negativization (p = 0.002). Conversely, having anti-RBD antibodies ≥ 809 BAU/mL and an IFN-γ-specific T cell response ≥ 16 pg/mL were associated with a shorter time to swab-negativization (p = 0.051 and p = 0.018, respectively). In conclusion, the immunological protection from SARS-CoV-2 infection may differ among PwMS according to DMTs.

Breakthrough SARS-CoV-2 infection in fully vaccinated patients with systemic lupus erythematosus: results from the COVID-19 Vaccination in Autoimmune Disease (COVAD) study.

OBJECTIVE: To determine the occurrence of breakthrough COVID-19 infections (BIs) in patients with systemic lupus erythematosus (SLE) compared with patients with other rheumatic autoimmune diseases (rAIDs), patients with non-rheumatic autoimmune diseases (nrAIDs), and healthy controls (HCs). METHODS: The study was based on data from 7035 fully vaccinated respondents to the online COVAD questionnaire with SLE (N = 852), rAIDs (N = 3098), or nrAIDs (N = 414), and HCs (N = 2671). BI was defined as COVID-19 infection occurring in individuals vaccinated with ≥ 2 doses (or 1 dose of J&J) ≥ 14 days after vaccination and not after 6 months since the last vaccine dose. Data were analysed using linear and logistic regression models. RESULTS: A total of 91/852 (10.7%) SLE patients reported at least one BI. The frequency of BIs in SLE patients was comparable to that among HCs (277/2671; p = 0.847) and patients with nrAID (39/414; p = 0.552) but higher than that among patients with other rAIDs (235/3098; p = 0.005). No demographic factors or treatments were associated with BIs in SLE patients (p ≥ 0.05 for all). Joint pain was more frequent in SLE patients than in HCs (odds ratio [OR]: 3.38; 95% confidence interval [CI]: 1.89-6.04; p < 0.001) or nrAID patients (OR: 2.44; 95% CI: 1.04-5.75; p = 0.041). Patient with SLE did not report a higher frequency of hospitalisation or need for advanced treatment for COVID-19 infection compared with disease controls and HCs, respectively. CONCLUSION: COVID-19 vaccination conferred similar protection against COVID-19 infection in terms of frequency and severity in patients with SLE to that reported by healthy individuals.

Immunity against conserved epitopes dominates after two consecutive exposures to SARS-CoV-2 Omicron BA.1.

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) exposure histories become increasingly complex through original and variant-adapted vaccines and infections with viral variants. Upon exposure to the highly altered Omicron spike glycoprotein, pre-immunized individuals predominantly mount recall responses of Wuhan-Hu-1 (wild-type)-imprinted memory B (BMEM) cells mostly targeting conserved non-neutralizing epitopes, leading to diminished Omicron neutralization. We investigated the impact of imprinting in individuals double/triple vaccinated with a wild-type-strain-based mRNA vaccine who, thereafter, had two consecutive exposures to Omicron BA.1 spike (breakthrough infection followed by BA.1-adapted vaccine). We found that depletion of conserved epitope-recognizing antibodies using a wild-type spike bait results in strongly diminished BA.1 neutralization. Furthermore, spike-specific BMEM cells recognizing conserved epitopes are much more prevalent than BA.1-specific BMEM cells. Our observations suggest that imprinted BMEM cell recall responses limit the induction of strain-specific responses even after two consecutive BA.1 spike exposures. Vaccine adaptation strategies need to consider that prior SARS-CoV-2 infections and vaccinations may cause persistent immune imprinting.

COVID-19 Vaccines Breakthrough Infections and Adverse Effects Reported by the Birzeit University Community in Palestine.

Background: Coronavirus disease (COVID-19) vaccines play an essential role in boosting immunity, preventing severe diseases, and alleviating the Covid-19 health crisis. Objective: This study aimed to explore the type and severity of short-term adverse reactions associated with BNT162 (Pfizer-BioNTech), mRNA 1273 (Moderna), and viral vector vaccines and to compare the incidence of post-vaccination Covid-19 infection among the Birzeit University community in Palestine. Methods: This questionnaire-based retrospective cross-sectional study was conducted among individuals who were vaccinated with at least one dose of any COVID-19 vaccine offered in Palestine during the COVID-19 pandemic. The study included participants aged 18 years and older who were vaccinated with Pfizer, Moderna, Sputnik Light, or Sputnik v. Results: A total of 558 participants who were administered COVID-19 vaccine were included in the study. Sputnik (239), Pfizer vaccine recipients (236), and Moderna vaccine recipients (83). Of the viral vector vaccine recipients, 57 (23.8%) had a post-vaccination infection, compared to 30 (12.7%) for Pfizer and seven (8.4%) for Moderna. Furthermore, the reported adverse effects in the viral victor group were higher than those in the Moderna and Pfizer groups (71.7, 66.3, and 61.9%, respectively). Chills, headache, fatigue, abdominal pain, and joint pain were significantly higher in the Viral Vector vaccine group than the Moderna and Pfizer vaccine. Vomiting, tiredness, and fatigue were significantly less likely to be complained of by Pfizer vaccine recipients compared to Moderna and Viral Vector vaccine recipients (p < 0.05). Conclusions: Breakthrough infections were associated with both viral vectors and mRNA; however, the mRNA vaccine had less reported post-vaccine infection. Furthermore, the Pfizer/BioNTech COVID-19 vaccine group reported fewer commonly reported side effects (fever, chills, headache, fatigue, muscle pain, joint pain, nausea, and dizziness), followed by the Moderna and viral vector vaccines. Females and underweight participants experienced more adverse effects with both vaccines, and fewer common side effects were reported by all participants.

SARS-CoV-2 reinfection broadens the antibody responses and promotes the phenotypic differentiation of virus-specific memory T cells in adolescents.

The emergence of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) Omicron subvariants raises concerns regarding the effectiveness of immunity acquired from previous Omicron subvariants breakthrough infections (BTIs) or reinfections (RIs) against the current circulating Omicron subvariants. In this study, we prospectively investigate the dynamic changes of virus-specific antibody and T cell responses among 77 adolescents following Omicron BA.2.3 BTI with or without subsequent Omicron BA.5 RI. Notably, the neutralizing antibodies (NAbs) titers against various detected SARS-CoV-2 variants, especially the emerging Omicron CH.1.1, XBB.1.5, XBB.1.16, EG.5.1, and JN.1 subvariants, exhibited a significant decrease along the time. A lower level of IgG and NAbs titers post-BTI was found to be closely associated with subsequent RI. Elevated NAbs levels and shortened antigenic distances were observed following Omicron BA.5 RI. Robust T cell responses against both Omicron BA.2- and CH.1.1-spike peptides were observed at each point visited. The exposure to Omicron BA.5 promoted phenotypic differentiation of virus-specific memory T cells, even among the non-seroconversion adolescents. Therefore, updated vaccines are needed to provide effective protection against newly emerging SARS-CoV-2 variants among adolescents.

How to prevent rubella epidemics and congenital rubella syndrome: lessons from 42 years of longitudinal epidemiology in Osaka Prefecture, Japan (1982-2023).

BACKGROUND: Despite the introduction of rubella-containing vaccine into routine immunization in 1977, rubella has not been eliminated in Japan. This study aimed to validate the immunization strategy and to highlight the crucial elements of elimination program. METHODS: We scrutinized cases of rubella and congenital rubella syndrome (CRS). Additionally, we analyzed the national vaccination coverage, seroprevalence, and number of maternal rubella-related spontaneous or artificial fetal deaths. RESULTS: The shift from selective to universal immunization significantly reduced rubella cases coupled with increased seroprevalence in children. However, rubella resurged in 2012-2013 and 2018-2019, which was virologically and serologically confirmed to be associated with imported rubella virus (RuV) and susceptible males. Although the disease burden of CRS may have been suppressed in the past by the large number of spontaneous or artificial fetal deaths, the incidence rate of CRS was comparable to that of the 1960s to 1980s. Cases of breakthrough infection and CRS were identified in females who were considered to have a history of single-dose vaccination. CONCLUSIONS: Even with universal immunization, future epidemics and severe outcomes cannot be prevented unless immunization gaps are closed. Furthermore, CRS and breakthrough infection are not completely prevented by single-dose vaccination, indicating the need for second-dose vaccination.

Antigenic sin and multiple breakthrough infections drive converging evolution of COVID-19 neutralizing responses.

Understanding the evolution of the B cell response to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) variants is fundamental to design the next generation of vaccines and therapeutics. We longitudinally analyze at the single-cell level almost 900 neutralizing human monoclonal antibodies (nAbs) isolated from vaccinated people and from individuals with hybrid and super hybrid immunity (SH), developed after three mRNA vaccine doses and two breakthrough infections. The most potent neutralization and Fc functions against highly mutated variants belong to the SH cohort. Repertoire analysis shows that the original Wuhan antigenic sin drives the convergent expansion of the same B cell germlines in vaccinated and SH cohorts. Only Omicron breakthrough infections expand previously unseen germ lines and generate broadly nAbs by restoring IGHV3-53/3-66 germ lines. Our analyses find that B cells initially expanded by the original antigenic sin continue to play a fundamental role in the evolution of the immune response toward an evolving virus.

BCG vaccination of healthcare workers for protection against COVID-19: 12-month outcomes from an international randomised controlled trial.

OBJECTIVES: Bacille Calmette-Guérin (BCG) vaccine has immunomodulatory effects that may provide protection against unrelated infectious diseases. We aimed to determine whether BCG vaccination protects adults against COVID-19. DESIGN: Phase III double-blind randomised controlled trial. SETTING: Healthcare centres in Australia, Brazil, the Netherlands, Spain, and the United Kingdom during the COVID-19 pandemic. PARTICIPANTS: 3988 healthcare workers with no prior COVID-19 and no contraindication to BCG. INTERVENTION: Randomised 1:1 using a web-based procedure to receive a single 0.1 mL intradermal dose of BCG-Denmark (BCG group, n = 1999) or saline (placebo group, n = 1989). MAIN OUTCOME MEASURES: Difference in incidence of (i) symptomatic and (ii) severe COVID-19 during the 12 months following randomisation in the modified intention to treat (mITT) population (confirmed SARS-CoV-2 naïve at inclusion). RESULTS: Of the 3988 participants randomised, 3386 had a negative baseline SARS-CoV-2 test and were included in the mITT population. The 12-month adjusted estimated risk of symptomatic COVID-19 was higher in the BCG group (22.6%; 95% confidence interval [CI] 20.6 to 24.5%) compared with the placebo group (19.6%; 95% CI 17.6 to 21.5%); adjusted difference +3.0% points (95% CI 0.2 to 5.8%; p = 0.04). The 12-month adjusted estimated risk of severe COVID-19 (mainly comprising those reporting being unable to work for ≥3 consecutive days) was 11.0% in the BCG group (95% CI 9.5 to 12.4%) compared with 9.6% in the placebo group (95% CI 8.3 to 11.1%); adjusted difference +1.3% points (95% CI -0.7 to 3.3%, p = 0.2). Breakthrough COVID-19 (post COVID-19 vaccination) and asymptomatic SARS-CoV-2 infections were similar in the two groups. There were 18 hospitalisations due to COVID-19 (11 in BCG group, 7 in placebo group; adjusted hazard ratio 1.56, 95% CI 0.60 to 4.02, p = 0.4) and two deaths due to COVID-19, both in the placebo group. CONCLUSIONS: Compared to placebo, vaccination with BCG-Denmark increased the risk of symptomatic COVID-19 over 12 months among healthcare workers and did not decrease the risk of severe COVID-19 or post-vaccination breakthrough COVID-19. TRIAL REGISTRATION: ClinicalTrials.gov NCT04327206.

Breakthrough COVID-19 Infections after Booster SARS-CoV-2 Vaccination in a Greek Cohort of People Living with HIV during the Delta and Omicron Waves.

INTRODUCTION: Currently approved SARS-CoV-2 vaccines have been proven effective in protecting against severe COVID-19; however, they show variable efficacy against symptomatic infection and disease transmission. We studied the breakthrough COVID-19 infection (BTI) after booster vaccination against SARS-CoV-2 in people living with HIV (PWH). METHODS: This was a retrospective, single-center, descriptive cohort study involving PWH, who were followed in the HIV Clinic of "Attikon" University Hospital in Athens, Greece. A BTI was defined as a case of laboratory-confirmed COVID-19 occurring at least 14 days after the third (booster) vaccine dose. RESULTS: We studied 733 PWH [males: 89%, mean age: 45.2 ± 11.3 years, mean BMI: 26.1 ± 4.1, HIV stage at diagnosis (CDC classification): A/B/C = 80/9/11%, MSM: 72.6%] with well-controlled HIV infection. At least one comorbidity was recorded in 54% of cases. A history of ≥1 vaccination was reported by 90%, with 75% having been vaccinated with ≥3 vaccines. Four hundred and two (55%) PWH had a history of COVID-19 and 302 (41.2%) had a BTI, with only 15 (3.7%) needing hospitalization. Only one patient was admitted to the ICU, and no death was reported. Regarding BTI after booster dose, increased age (OR = 0.97, 95% CI: 0.96-0.99, per 1-year increase), and COVID-19 infection prior to booster dose (OR = 0.38, 95% CI: 0.21-0.68) were associated with a lower likelihood for BTI, whereas higher BMI (OR = 1.04, 95% CI: 1.01-1.08) and MSM as a mode of HIV transmission were associated with increased risk (OR = 2.59, 95% CI: 1.47-4.56). The incidence rate of total COVID-19 and BTI followed the epidemic curve of the general population, with the highest incidence recorded in June 2022. CONCLUSIONS: A significant proportion of PWH with well-controlled HIV infection experienced a BTI, with the majority of them having mild infection. These data, which include the period of Omicron variant predominance, confirm the importance of vaccination in the protection against severe COVID-19.

Neutralization of SARS-CoV-2 Omicron XBB.1.5 and JN.1 variants after COVID-19 booster-vaccination and infection.

SARS-CoV-2 Omicron lineages continue to emerge and evolve into new sublineages, causing infection waves throughout 2022 and 2023, which has been attributed to immune escape. We examined neutralizing antibody responses to the recently emerged SARS-CoV-2 JN.1 variant in comparison to ancestral D614G and Omicron BA.1, BA.2, BA.5, and XBB.1.5 variants. We tested 79 human sera from cohorts with different combinations of vaccinations and infections, including 23 individuals who had been repeatedly exposed to Omicron. Individuals with a monovalent XBB.1.5 vaccine booster or XBB.1.5 breakthrough infection had robust antibody levels against all variants tested; however, JN.1 evaded antibodies in individuals after single Omicron BA.1, BA.2 or BA.5 breakthrough infections. Moreover, in the non-vaccinated cohort, serum antibodies demonstrated almost no cross-neutralization activities against D614G, XBB.1.5 and JN.1. after infections with earlier Omicron variants. These findings show that SARS-CoV-2-immunity is heterogeneous, depending on different combinations of vaccinations and infections, and emphasize the importance of considering different immune-backgrounds when evaluating novel variants.

Impact of vaccination on SARS-CoV-2 evolution and immune escape variants.

Vaccines and host genetic factors can influence the SARS-CoV-2 evolution and emergence of new variants. Even vaccinated cases get affected as virus continues to evolve, raising concerns about vaccine efficacy and the emergence of immune escape variants. Here, we have analyzed 2295 whole-genome sequences of SARS-CoV-2 collected from vaccinated and unvaccinated cases to evaluate the impact of vaccines on virus diversity within hosts. Our comparative analysis revealed a significant higher incidence of intra-host single nucleotides variants (iSNVs) in vaccinated cases compared to unvaccinated ones (p value<0.0001). Furthermore, we have found that specific mutational processes, including APOBEC (C > T) mediated and ADAR1 (A > G) mediated mutations, were found more prevalent in vaccinated cases. Vaccinated cases exhibited higher accumulation of nonsynonymous mutation than unvaccinated cases. Fixed iSNVs were predominantly located in the ORF1ab and spike genes, several key omicron defining immune escape variants S477N, Q493R, Q498R, Y505H, L452R, and N501Y were identified in the RBD domain of spike gene in vaccinated cases. Our findings suggest that vaccine plays an important role in the evolution of the virus genome. The virus genome acquires random mutations due to error-prone replication of the virus, host modification through APOBEC and ADAR1 mediated editing mechanism, and oxidative stress. These mutations become fixed in the viral population due to the selective pressure imposed by vaccination.