SARS-CoV-2 Omicron XBB lineage spike structures, conformations, antigenicity, and receptor recognition.

A recombinant lineage of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) Omicron variant, named XBB, appeared in late 2022 and evolved descendants that successively swept local and global populations. XBB lineage members were noted for their improved immune evasion and transmissibility. Here, we determine cryoelectron microscopy (cryo-EM) structures of XBB.1.5, XBB.1.16, EG.5, and EG.5.1 spike (S) ectodomains to reveal reinforced 3-receptor binding domain (RBD)-down receptor-inaccessible closed states mediated by interprotomer RBD interactions previously observed in BA.1 and BA.2. Improved XBB.1.5 and XBB.1.16 RBD stability compensated for stability loss caused by early Omicron mutations, while the F456L substitution reduced EG.5 RBD stability. S1 subunit mutations had long-range impacts on conformation and epitope presentation in the S2 subunit. Our results reveal continued S protein evolution via simultaneous optimization of multiple parameters, including stability, receptor binding, and immune evasion, and the dramatic effects of relatively few residue substitutions in altering the S protein conformational landscape.

Neutralizing Antibody Immune Correlates for a Recombinant Protein Vaccine in the COVAIL Trial.

For COVAIL recipients of a COVID-19 Sanofi booster vaccine, neutralizing antibody titers were assessed as a correlate of risk (CoR) of COVID-19. Peak and exposure-proximal titers were inverse CoRs with covariate-adjusted hazard ratios (95% confidence intervals) 0.30 (0.11, 0.78) and 0.25 (0.07, 0.85) per 10-fold increase in weighted average titer.

Leveraging the potential of bacterial lateral gene transfer in boosting the efficacy of an edible probiotic prototype yogurt vaccine for COVID-19.

Administration of coronavirus disease-2019 (COVID-19) vaccines with appropriate booster doses through painful injections under clinical supervision was challenging during the recent COVID-19 pandemic. As an alternative solution, we designed a safer, edible probiotic yogurt vaccine prototype (YoVac) that can be orally consumed by circumventing painful injections and clinical supervision. We hypothesized that YoVac prepared using Lactobacillus carrying an antigen coding gene (donor) can transfer the same to other bacteria (recipients) in the human gut microbiome (hgMb) through lateral gene transfer (LGT) for boosted antigen levels potentially triggering a robust immune response. In this study we confirmed the in vitro LGT efficiency of a plasmid (pRBD-Ampr) containing severe acute respiratory syndrome coronavirus-2 (SARS CoV-2) spike protein-receptor binding domain (RBD) coding gene along with an ampicillin-resistance gene (selection marker) from the probiotic Lactobacillus (donor) cultured from homemade yogurt to E. coli and Helicobacter pylori (recipients). Both the donor and recipient bacteria not only exhibited ampicillin-resistance from pRBD-Ampr but also expressed RBD protein. Furthermore, Lactobacillus isolated from YoVac consistently showed the expression of RBD protein over a period of one month confirming the shelf life of our prototype stored at 4 °C. Taken together, our in vitro results provide a preliminary basis for the potential in vivo transfer of RBD coding gene from YoVac to other bacterial species in the hgMb through LGT and may potentially boost the vaccine dosage by delegating them.

Influences on COVID-19 booster uptake among adults intending to receive a booster: a qualitative study.

Bivalent COVID-19 vaccine boosters have been recommended for all Americans 12 years of age and older. However, uptake remains suboptimal with only 17% of the United States (US) population boosted as of May 2023. This is a critical public health challenge for mitigating the ongoing effects of COVID-19 infection. COVID-19 booster uptake is not currently well understood, and few studies in the US have explored the vaccination process for booster uptake in a 'post-pandemic' context. This study fills gaps in the literature through qualitative analysis of interviews with a racially/ethnically diverse sample of Arkansans who received the COVID-19 vaccine main series and expressed intent to receive a booster (n = 14), but had not yet received the COVID-19 booster at the time we recruited them. All but one did not receive the booster by the time of the interview. Participants described influences on their vaccination behavior and uptake of boosters including reduced feelings of urgency; continued concerns about the side effects; social contagion as a driver of urgency; increasing practical barriers to access and missing provider recommendations. Our findings highlight the importance of considering vaccination as an ongoing, dynamic process drawing on past/current attitudes, prior experience, perceptions of risk and urgency and practical barriers. Based on these findings, healthcare providers should continue to provide strong, consistent recommendations for COVID-19 boosters to patients, even among those with histories of vaccine uptake.

Current German Recommendations and International Research on the Use of COVID-19 Boosters among Health Care Providers in 2024: A Narrative Review.

While the World Health Organization (WHO) has de-escalated coronavirus disease 2019 (COVID-19) from a global health emergency, ongoing discussions persist as new viral variants. This article aimed to consolidate German recommendations and international research to offer health care providers (HCPs) a comprehensive guide on COVID-19 boosters in 2024. The review outlines key recommendations from the German Robert Koch Institute. HCPs should receive COVID-19 boosters at least 12 months after their last vaccination or COVID-19 infection, contingent on the prevalent viral variant(s) in the region. However, excessive doses and/or frequent boosters, especially with mRNA vaccines, may lead to immune imprinting, T-cell exhaustion, and immunoglobulin (Ig) switching. Notably, this review highlights the significance of Ig, particularly IgA and IgG subclasses, in influencing infection risk and disease progression. Furthermore, it explores the implications of mRNA vaccine technology and potential adverse effects related to excessive dosing. In conclusion, this article provides a comprehensive analysis of COVID-19 vaccine boosters for HCPs, synthesising current recommendations, scientific debates, and considerations for optimising protection against SARS-CoV-2 in the evolving landscape of the post-pandemic era.

Vaccination status among COVID-19 patients and duration of Polymerase Chain Reaction test positivity: evaluation of immunization schedule and type of vaccine.

Background: The introduction of the vaccine against SARS-CoV-2 has represented a cornerstone in the containment of the pandemic. Our aim was to assess the vaccination schedules in relation to the infection free interval and to the duration of positivity in case of infection. Study design: This study involves the SARS-CoV-2 infected people managed by the Local Health Authority ASL 1 Abruzzo. The data collected included: vaccine administration date, vaccine type, information on the Polymerase Chain Reaction test positivity, and demographic variables, such as age and sex. Methods: The duration of Polymerase Chain Reaction test positivity was assessed in relation to the vaccination status, the vaccine type and the time interval between the last vaccination dose and the first nasopharyngeal positive swab over the considered period. Results: The infection duration (DAYS) was significantly shorter in subjects vaccinated with a booster dose than unvaccinated subjects (12.8 vs 14.6; p<0.0001) and subjects vaccinated with the primary series only (12.8 vs 14.1; p<0.0001). Duration of PCR positivity was shorter with heterologous immunisation than with other vaccination schedules (p=0.0317). Conclusions: This study highlights, in a large cohort of patients, the association between vaccination schedule and the response to infection.

Characterization of Entry Pathways, Species-Specific Angiotensin-Converting Enzyme 2 Residues Determining Entry, and Antibody Neutralization Evasion of Omicron BA.1, BA.1.1, BA.2, and BA.3 Variants.

The SARS-CoV-2 Omicron variants were first detected in November 2021, and several Omicron lineages (BA.1, BA.2, BA.3, BA.4, and BA.5) have since rapidly emerged. Studies characterizing the mechanisms of Omicron variant infection and sensitivity to neutralizing antibodies induced upon vaccination are ongoing by several groups. In the present study, we used pseudoviruses to show that the transmembrane serine protease 2 (TMPRSS2) enhances infection of BA.1, BA.1.1, BA.2, and BA.3 Omicron variants to a lesser extent than ancestral D614G. We further show that Omicron variants have higher sensitivity to inhibition by soluble angiotensin-converting enzyme 2 (ACE2) and the endosomal inhibitor chloroquine compared to D614G. The Omicron variants also more efficiently used ACE2 receptors from 9 out of 10 animal species tested, and unlike the D614G variant, used mouse ACE2 due to the Q493R and Q498R spike substitutions. Finally, neutralization of the Omicron variants by antibodies induced by three doses of Pfizer/BNT162b2 mRNA vaccine was 7- to 8-fold less potent than the D614G. These results provide insights into the transmissibility and immune evasion capacity of the emerging Omicron variants to curb their ongoing spread. IMPORTANCE The ongoing emergence of SARS-CoV-2 Omicron variants with an extensive number of spike mutations poses a significant public health and zoonotic concern due to enhanced transmission fitness and escape from neutralizing antibodies. We studied three Omicron lineage variants (BA.1, BA.2, and BA.3) and found that transmembrane serine protease 2 has less influence on Omicron entry into cells than on D614G, and Omicron exhibits greater sensitivity to endosomal entry inhibition compared to D614G. In addition, Omicron displays more efficient usage of diverse animal species ACE2 receptors than D614G. Furthermore, due to Q493R/Q498R substitutions in spike, Omicron, but not D614G, can use the mouse ACE2 receptor. Finally, three doses of Pfizer/BNT162b2 mRNA vaccination elicit high neutralization titers against Omicron variants, although the neutralization titers are still 7- to 8-fold lower those that against D614G. These results may give insights into the transmissibility and immune evasion capacity of the emerging Omicron variants to curb their ongoing spread.

Ad5-nCoV booster and Omicron variant breakthrough infection following two doses of inactivated vaccine elicit comparable antibody levels against Omicron variants.

Little information is available for antibody levels against SARS-CoV-2 variants of concern induced by Omicron breakthrough infection and a third booster with an inactivated vaccine (InV) or Ad5-nCoV in people with completion of two InV doses. Plasma was collected from InV pre-vaccinated Omicron-infected patients (OIPs), unvaccinated OIPs between 0 and 22 days, and healthy donors (HDs) 14 days or 6 months after the second doses of an InV and 14 days after a homogenous booster or heterologous booster of Ad5-nCoV. Anti-Wuhan-, Anti-Delta-, and Anti-Omicron-receptor binding domain (RBD)-IgG titers were detected using enzyme-linked immunosorbent assay. InV pre-vaccinated OIPs had higher anti-Wuhan-, anti-Delta-, and anti-Omicron-RBD-IgG titers compared to unvaccinated OIPs. Anti-Wuhan-RBD-IgG titers sharply increased in InV pre-vaccinated OIPs 0-5 days postinfection (DPI), while the geometric mean titers (GMTs) of anti-Delta- and anti-Omicron-RBD-IgG were 3.3-fold and 12.0-fold lower. Then, the GMT of anti-Delta- and anti-Omicron-RBD-IgG increased to 35 112 and 28 186 during 11-22 DPI, about 2.6-fold and 3.2-fold lower, respectively, than the anti-Wuhan-RBD-IgG titer. The anti-Wuhan-, anti-Delta-, and anti-Omicron-RBD-IgG titers declined over time in HDs after two doses of an InV, with 25.2-fold, 5.6-fold, and 4.5-fold declination, respectively, at 6 months relative to the titers at 14 days after the second vaccination. Anti-Wuhan-, anti-Delta-, and anti-Omicron-RBD-IgG titers elicited by a heterologous Ad5-nCoV booster were significantly higher than those elicited by an InV booster, comparable to those in InV pre-vaccinated OIPs. InV and Ad5-nCoV boosters could improve humoral immunity against Omicron variants. Of these, the Ad5-nCoV booster is a better alternative.

Humoral and cellular response after BNT162b2 vaccine booster in hemodialysis patients and kidney transplant recipients.

BACKGROUND: Vulnerable populations, such as hemodialysis (HD) patients and kidney transplant (RTx) recipients, have priority for anti-COVID-19 vaccination, because of their impaired immune status. Here, we investigated the immune response after vaccination with BNT162b2 (two doses plus booster) in HD and RTx patients. METHODS: A prospective, observational study was started in two homogeneous groups of 55 HD and 51 RTx patients previously matched from a cohort of 336 patients. Anti-RBD IgG levels, assayed after the second dose with BNT162b2 mRNA, were used to stratify subjects into quintiles. After the second dose and after booster, anti-RBD and IGRA test were evaluated in RTx and HD, belonging to the first and fifth quintiles. RESULTS: After the second dose of vaccine, the median circulating levels of anti-RBD IgG were significantly higher in HD (1456 AU/mL) compared to RTx (27.30 AU/mL). IGRA test showed significantly higher values in the HD (382 mIU/mL) compared with the RTx (73 mIU/mL). After the booster, humoral response increased significantly in both HD (p = 0.0002) and RTx groups (p = 0.009), whereas the T-cellular immunity remained essentially stable in most patients. In RTx patients with a low humoral response after the second dose, the third dose did not significantly strengthen either humoral or cellular immunity. CONCLUSIONS: For HD and RTx, there is great variability in the humoral response to anti-COVID-19 vaccination, with a stronger response in the HD group. The booster dose was ineffective at reinforcing the humoral and cellular immune response in most RTx patients hyporesponsive to the second dose.

Antibody Response of Heterologous vs Homologous Messenger RNA Vaccine Boosters Against the Severe Acute Respiratory Syndrome Coronavirus 2 Omicron Variant: Interim Results from the PRIBIVAC Study, a Randomized Clinical Trial.

BACKGROUND: Waning antibody levels post-vaccination and the emergence of variants of concern (VOCs) capable of evading protective immunity have raised the need for booster vaccinations. However, which combination of coronavirus disease 2019 (COVID-19) vaccines offers the strongest immune response against the Omicron variant is unknown. METHODS: This randomized, participant-blinded, controlled trial assessed the reactogenicity and immunogenicity of different COVID-19 vaccine booster combinations. A total of 100 BNT162b2-vaccinated individuals were enrolled and randomized 1:1 to either homologous (BNT162b2 + BNT162b2 + BNT162b2; "BBB") or heterologous messenger RNA (mRNA) (BNT162b2 + BNT162b2 + mRNA-1273; "BBM") booster vaccine. The primary end point was the level of neutralizing antibodies against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) wild-type and VOCs at day 28. RESULTS: A total of 51 participants were allocated to BBB and 49 to BBM; 50 and 48, respectively, were analyzed for safety and immunogenicity outcomes. At day 28 post-boost, mean SARS-CoV-2 spike antibody titers were lower with BBB (22 382 IU/mL; 95% confidence interval [CI], 18 210 to 27 517) vs BBM (29 751 IU/mL; 95% CI, 25 281 to 35 011; P = .034) as was the median level of neutralizing antibodies: BBB 99.0% (interquartile range [IQR], 97.9% to 99.3%) vs BBM 99.3% (IQR, 98.8% to 99.5%; P = .021). On subgroup analysis, significant higher mean spike antibody titer, median surrogate neutralizing antibody level against all VOCs, and live Omicron neutralization titer were observed only in older adults receiving BBM. Both vaccines were well tolerated. CONCLUSIONS: Heterologous mRNA-1273 booster vaccination compared with homologous BNT123b2 induced a stronger neutralizing response against the Omicron variant in older individuals. CLINICAL TRIALS REGISTRATION: NCT05142319.

BNT162b2 mRNA COVID-19 vaccine booster induces seroconversion in patients with B-cell non-Hodgkin lymphoma who failed to respond to two prior vaccine doses.

This prospective study evaluated seroconversion rates in response to BNT162b2 (Pfizer-BioNTech) COVID-19 vaccine booster in 44 B-cell non-Hodgkin lymphoma (B-NHL) patients who failed to respond to two prior doses [42 previously exposed to anti-CD20 monoclonal antibodies (moAbs) including 13 under maintenance treatment]. Seroconversion was obtained in 29.5% of the patients. Longer time from last anti-CD20 moAb (>6 months) and diagnosis of aggressive lymphoma compared to other, incurable B-NHLs were associated with increased seroconversion rates (47.8% vs.10.5%, p = 0.019 and 50% vs. 17.9%, p = 0.025 respectively). Thus, seronegative patients with B-NHL that completed anti-CD20 therapy more than 6 months prior to the booster have greater chances to achieve seroconversion.

Current perspectives regarding SARS-CoV-2 vaccination in chronic lymphocytic leukemia.

In immunocompetent people, the mRNA vaccines BNT162b2 and mRNA-1273 have been shown to be safe and effective against coronavirus disease of 2019 (COVID-19). However, results of cohort studies and meta-analyses have indicated that the degree of humoral response to SARS-CoV-2 vaccines in patients with chronic lymphocytic leukemia (CLL) appears to be lower than that observed in the general population. These inadequate responses are mainly related to the disease itself and to the immunosuppressive effect of therapies administered. In the specific context of CLL, enrolling patients with sub-optimal vaccine-response in pivotal vaccine trials could be considered as an appropriate approach to improve response to the COVID-19 vaccine. These clinical trials should also address the issues of regularity and timing of vaccine booster doses or re-vaccinations, especially in patients undergoing therapy with pathway-targeting agents and anti-CD20 monoclonal antibodies. However, since hypogammaglobulinemia is a serious consequence of CLL, patients who do not have a detectable antibody response should be natural candidates for preventive antibody therapy.

Redressing COVID-19 vaccine inequity amidst booster doses: charting a bold path for global health solidarity, together.

BACKGROUND: With large swathes of the world's population-majority clustered in low- and middle-income countries-still yet to receive the minimum of two doses of the COVID-19 vaccine; The need to address the failures of international solidarity to equitably distribute COVID-19 vaccines is now more urgent than ever to help curb the pandemic and prevent future variants. However, many high-income countries have adopted a "me first" approach, proceeding to offer COVID-19 booster doses to their entire populations, including those at least risk of severe illness, whilst the rest of the world is left unvaccinated or partially vaccinated with one dose for even their most vulnerable communities. MAIN BODY: COVID-19 vaccine inequity places the health of the global population at risk and exacerbates socio-economic repercussions, especially in low- and middle-income countries. Initiatives launched to combat vaccine inequity such as the Fair Allocation Framework for the COVID-19 Vaccines (COVAX) have been unsuccessful as several governments, primarily from high-income countries, have scaled down their contributions to the initiative. Furthermore, COVAX has not seriously engaged with the Access to COVID-19 Tools (ACT) Health Systems Connector, as was originally intended, leading to crucial health systems components critical to vaccine delivery to be overlooked. Several strategies can be employed to help achieve the desired global immunization goals, such as Intellectual Property waivers, increased donations, and activation of new COVID-19 vaccine manufacturing hubs. In addition, continued advocacy for vaccine equity by all involved and affected stakeholders, as well as critical amendments to existing or upcoming legislation and funding mechanisms will help address the shortcomings of current inequitable vaccine distribution. CONCLUSIONS: Global solidarity and collective action through pandemic governance mechanisms are urgently needed to ensure vaccine equity. These interventions are vital to rapidly mitigate ongoing health and humanitarian crises and ultimately curb the pandemic, sooner rather than later.

Bacillus Calmette-Guérin-Induced Human Mast Cell Activation Relies on IL-33 Priming.

Bacillus Calmette-Guérin (BCG) vaccine is an attenuated strain of Mycobacterium bovis that provides weak protection against tuberculosis (TB). Mast cells (MCs) are tissue-resident immune cells strategically that serve as the first line of defence against pathogenic threats. In this study, we investigated the response of human MCs (hMCs) to BCG. We found that naïve hMCs exposed to BCG did not secrete cytokines, degranulate, or support the uptake and intracellular growth of bacteria. Since we could show that in hMCs IL-33 promotes the transcription of host-pathogen interaction, cell adhesion and activation genes, we used IL-33 for cell priming. The treatment of hMCs with IL-33, but not IFN-γ, before BCG stimulation increased IL-8, MCP-1 and IL-13 secretion, and induced an enhanced expression of the mycobacteria-binding receptor CD48. These effects were comparable to those caused by the recombinant Mycobacterium tuberculosis (Mtb) 19-KDa lipoprotein. Finally, stimulation of hMCs with IL-33 incremented MC-BCG interactions. Thus, we propose that IL-33 may improve the immunogenicity of BCG vaccine by sensitising hMCs.

Acceptance, attitudes, and barriers of vaccine booster dose among nursing students: A multicounty survey.

AIM: This study investigated the acceptance and attitudes of nursing students toward the COVID-19 vaccine booster dose in two Gulf Cooperation countries and the potential influencing factors for taking a COVID-19 vaccine booster dose. BACKGROUND: The world is still battling coronavirus because of the emerged of variants and because protection against COVID-19 has waned over time. Vaccination is a powerful and effective method of reducing the outbreak of COVID-19 and decreasing the loss of lives. DESIGN: This research was a survey using a cross-sectional design. METHODS: The study's sample was two nursing colleges. The study tool was adopted according to recent information concerning the COVID-19 vaccine published by the World Health Organization. Data was collected through an online survey during March to April. RESULTS: A total of 216 nursing students completed the survey, of which 69.4% (n = 150) were male students and more than half of the participants were from Saudi Arabia (55.1%, n = 119). Two-thirds of the students (75.5%, n = 161) reported that they agreed to receive a COVID-19 vaccine booster. The total attitude scores for the students ranged from 28 to 35, with a mean score of 15.8 (SD = 2.5), representing 73% of the highest possible score, with 79.3% classified as 'positive attitude toward booster dose of COVID-19'. Vaccine booster might cause infection, vaccine booster ineffective, worried about adverse effects and not safe were major barriers influencing the acceptance of the COVID-19 vaccine booster. CONCLUSION: Nursing students revealed high acceptance rates related to COVID-19 vaccine booster. However, more attention should be paid from nursing educators to barriers influencing the acceptance of the COVID-19 vaccine booster. Preparing nursing students with positive attitude of COVID-19 vaccine booster is very important to patient and community safety. IMPLICATIONS FOR NURSING MANAGEMENT: Nursing educators and managers must make an effort to educate the nursing students regarding safety and effectiveness from COVID-19 vaccine booster and ensure that it is necessary to reduce their perception of the injury of COVID-19 infection.

Uptake of COVID-19 Booster Dose among Saudi Arabian Population.

Backgroundand objectives: Although several vaccines have been produced and administered around the world, new SARS-CoV-2 worsened the COVID-19 infection risk and impacted the initial vaccine dosage effectiveness. Based on studies indicating that the third and fourth COVID-19 vaccine doses significantly reduced COVID-19 transmission, Saudi Arabia has been administering COVID-19 booster vaccine doses to its citizens. The purpose of this study was to evaluate the uptake of the COVID-19 vaccine booster in relation to the socio-demographic characteristics and other associated factors among the Saudi population. Materials and Methods: This study was an online analytical cross-sectional study using a self-administered questionnaire. Pearson Chi-square test and multiple logistic regression analyses were used to determine factors associated with the uptake of COVID-19 booster dose vaccines. Results: A total of 2332 responded to our study. Overall, 527 (22.6%) participants had received a booster dose. An age of 55 and above (aOR: 5.415; 95% CI: 2.719-10.783), Eastern region (aOR: 2.513; 95% CI: 1.566-4.033), history of influenza vaccination at annual intervals (aOR: 2.387; 95% CI: 1.730-3.293), the first dose of Moderna vaccine (aOR: 1.324; 95% CI: 1.160-1.510), and cancer (aOR: 2.161; 95% CI: 1.218-3.879) were independent factors most associated with a higher uptake of the COVID-19 vaccine booster dose. In contrast, the second dose of Moderna vaccine (aOR: 0.794; 95% CI: 0.683-0.922), AstraZeneca vaccine (aOR: 0.691; 95% CI: 0.509-0.939), strong symptoms from side effects after the second dose of the COVID-19 vaccine (aOR: 0.615; 95% CI: 0.404-0.935) were independent factors most associated with a lower uptake of the COVID-19 vaccine booster dose. Conclusions: Our findings indicate low COVID-19 vaccine booster uptake. This necessitates the need for strategies to address discouraging factors of the COVID-19 vaccine booster dose uptake and engage the Saudi population to raise awareness about the importance of the booster dose.

Immune responses to hepatitis B immunization 10-18 years after primary vaccination: a population-based cohort study.

We evaluated the immune response to neonatal HBV immunization in children of infected parents 10-18 years after primary vaccination. Healthy individuals immunized with an infantile course of three doses of HBV vaccine were tested for persistence of anti-HB surface antibody (HBsAb). Those with an HBsAb level of <10 IU/mL received a booster dose of the vaccine with subsequent doses to those without protective titres. HBsAb concentrations were determined 4 weeks after each dose of the booster vaccine. The data were analysed separately for three age groups: 10-11, 12-14 and 15-18 years old. A total of 541 healthy individuals were studied. The highest seroprotection rate of 48% was observed in the youngest vaccinees (10-11 years old). This declined to 26.5% in the oldest (15-18 years old) group (P = 0.008). The youngest vaccinees showed the highest rate of anamnestic immune responses (96%). However, 25% of oldest individuals failed to mount an anamnestic immune response in challenge with a booster dose of the vaccine (P = 0.005), suggesting waning immunity with increasing age. Age (OR: 0.80; P = 0.01) and prebooster HBsAb levels (OR: 0.37; P = 0.01) identified responders to first booster doses of the vaccine by logistic regression analysis. The majority of high-risk vaccinees showed anamnestic immune response 10-11 years after primary immunization. However, we found a significant proportion (25%) of older individuals with no anamnetic response, which suggests a waning of immune memory. Detailed long-term follow-up studies are necessary to determine the risk of natural infection among these individuals before a booster schedule can be recommended.

Global disparities in COVID-19 vaccine booster dose (VBD) acceptance and hesitancy: An updated narrative review.

The global deployment of COVID-19 vaccine booster dose (VBD) has been recognized as a promising therapeutic alliance to provide repeated immunity against the arrival of new variants. Despite scientific evidence supports the effectiveness of periodic doses, COVID-19 vaccine booster reluctance continues to thrive. This narrative review aimed to examine global COVID-19 vaccine booster dose (VBD) acceptance and summarize an up-to-date assessment of potential antecedents associated with VBD acceptance. A comprehensive search was performed in several reputable databases such as Medline (via PubMed), Scopus, Google scholar, and Web of Science from June 10th, 2023, to August 1st, 2023. All relevant descriptive and observational studies on COVID-19 VBD acceptance and hesitancy were included in this review. A total of fifty-eight (58) studies were included, with Asia representing the highest count with thirty-one (53%) studies, Europe with eleven (19 %), the United States with nine (16 %), and other regions (Africa and multi-ethnic) with seven (12 %). Worldwide, the pooled COVID-19 VBD acceptance rate was 77.09 % (95 % CI: 76.28-78.18), VBD willingness (n) = 164189, and the total sample (N) = 212,990. The highest and the lowest VBD acceptance rate was reported in Europe and American regions, respectively, 85.38 % (95 % CI: 85.02-85.73, (n) = 32,047, (N = 37,533) vs. 66.92 % (95 % CI: 66.56-67.4), (n) = 29335, (N) = 43,832. However, Asia and multi-ethnic areas reported moderately high VBD acceptance rate 79.13 % (95 % CI: 78.77-79.23, (n) = 93,994, (N) = 11,8779) and 72.16 % (95 % CI: 71.13-72.93, (n) = 9276, (N) = 12,853), respectively. The most common and key antecedents of COVID-19 VBD acceptance and hesitancy across the countries were "equal safety", "efficacy", "effectiveness", "post-vaccination side effects", "community protection" "family protection", "risk-benefit ratio", "booster necessity", "trust", and "variants control". Disparities in the uptake of COVID-19 VBD were observed globally, with the highest rates found in Europe, and the lowest rates in American regions. Multiple potential antecedents including safety, efficacy, and post-vaccination side effects were associated with VBD acceptance and hesitancy.

Reported effectiveness of COVID-19 monovalent booster vaccines and hybrid immunity against mild and severe Omicron disease in adults: A systematic review and meta-regression analysis.

Background: Waning of COVID-19 vaccine efficacy/effectiveness (VE) has been observed across settings and epidemiological contexts. We conducted a systematic review of COVID-19 VE studies and performed a meta-regression analysis to improve understanding of determinants of waning. Methods: Systematic review of PubMed, medRxiv and the WHO-International Vaccine Access Center database summarizing VE studies on 31 December 2022. Studies were those presenting primary adult VE data from hybrid immunity or third/fourth mRNA COVID-19 monovalent vaccine doses [due to limited data with other vaccines] against Omicron, compared with unvaccinated individuals or individuals eligible for corresponding booster doses but who did not receive them. We used meta-regression models, adjusting for confounders, with weeks since vaccination as a restricted cubic spline, to estimate VE over time since vaccination. Results: We identified 55 eligible studies reporting 269 VE estimates. Most estimates (180/269; 67 %) described effectiveness of third dose vaccination; with 48 (18 %) and 41 (15 %) describing hybrid immunity and fourth dose effectiveness, respectively, mostly (200; 74 %) derived from test-negative design studies. Most estimates (176/269; 65 %) reported VE compared with unvaccinated comparison groups. Estimated VE against mild outcomes declined following third dose vaccination from 62 % (95 % CI: 58 % - 66 %) after 4 weeks to 48 % (41 % - 55 %) after 20 weeks. Fourth dose VE against mild COVID-19 declined from 48 % (41 % - 56 %) after 4 weeks to 47 % (19 % - 65 %) after 20 weeks. VE for severe outcomes was higher and declined in the three-dose group from 90 % (87 % - 92 %) after 4 weeks to 70 % (65 - 74 %) after 20 weeks. Conclusions: Time-since vaccination is an important determinant of booster dose VE, a finding which may support seasonal COVID-19 booster doses. Integration of VE and immunological parameters - and longer-term data including from other vaccine types - are needed to better-understand determinants of clinical protection.

Influence of Environmental Risk Exposure on the Determinants of COVID-19 Booster Vaccination in an Urban Thai Population.

This study aimed to identify the influence of environmental risk exposure levels on the predictive factors of COVID-19 booster dose vaccination in an urban Thai population in the post-pandemic era. Six study locations, including the three provinces with the highest environmental risk levels and the three provinces with the lowest environmental risk levels, were selected by calculating the environmental risk exposure indexes. Participants from the capital district of each province were chosen via the simple random sampling technique and interviewed using a structured questionnaire. A total of 1315 individuals were included in a sample in this study, and the best predictors of booster dose vaccination were determined using multiple regression analysis. The results showed that a high level of environmental risk exposure occurred in the provinces with a high number of total days exceeding the limits set for PM10 and high rates of mortality for lung cancer. The number of COVID-19 booster vaccinations given amount to 43.4% of the population during the post-COVID-19 pandemic period. Our multivariate analysis indicated that individuals in the working age group (≥25 years old); those with higher education (diploma degree and above); full-time employment (government and private sectors); those with high monthly incomes (≥USD144.1); and those in areas with the lowest risk level of environmental exposure significantly contributed to the number of booster dose vaccinations given during the post-pandemic period. To summarize, the rate of COVID-19 booster dose vaccination acceptance in Thailand was influenced by socio-economic factors with environmental concerns. These findings improve our understating of both the global pandemic and how environmental exposure affects behavioral change patterns and could improve the effectiveness of post-pandemic management.