Modeling of waning immunity after SARS-CoV-2 vaccination and influencing factors

Modelling antibody dynamics in humans after different Ad26.COV2.S vaccination schemes

AIMS

To develop a semimechanistic model that describes the kinetic profile and variability of antibody (Ab) concentrations following vaccination with Ad26.COV2.S at different doses and dosing intervals.

METHODS

Data were collected from participants randomized into 5 clinical trials receiving the Ad26.COV2.S vaccine. The model considered key elements of humoral immune response, dose proportionality and the evolutionary processes of the immune response. Interindividual variability and covariates were explored.

RESULTS

Fast and slow kinetic phases of Ab and their evolution over time were differentiated. After first and second administrations, Ab concentrations of both phases increased less than dose proportionally, indicating a saturation of B-cell production processes. Ab concentrations produced during the fast kinetic phase increased significantly after the second administration, indicating an underlying evolutive process after antigen exposures. For the slow kinetic phase, a less pronounced increase occurred after the second and third administrations but was relatively higher in subjects who had low concentrations after the first administration. Ab concentrations of the slow phase were higher in females and decreased with age. After multiple administrations, the fast phase had Ab maximum concentrations about 5 times higher than the slow phase. The limiting kinetic factors in the fast and slow phases were the elimination rates of Ab itself and Ab producing cells, respectively.

CONCLUSION

The model appears suitable to quantitatively describe the inter- and intraindividual kinetics of the immune response and the impact of covariates after multiple administrations of a vaccine.

Impact of SARS-CoV-2 vaccination and of seasonal variations on the innate immune inflammatory response

Introduction

The innate immune response is an important first checkpoint in the evolution of an infection. Although adaptive immunity is generally considered the immune component that retains antigenic memory, innate immune responses can also be affected by previous stimulations. This study evaluated the impact of vaccination on innate cell activation by TLR7/8 agonist R848, as well as seasonal variations.

Methods

To this end, blood samples from a cohort of 304 food and retail workers from the Quebec City region were collected during three visits at 12-week intervals. Peripheral blood mononuclear cells and polymorphonuclear neutrophils were isolated during the first and third visits and were stimulated with R848 to assess the innate immune response.

Results

Our results show that IL-8 production after stimulation decreased after vaccination. In addition, the IL-8 response was significantly different depending on the season when the visit occurred, for both COVID-19 vaccinated and unvaccinated individuals.

Discussion

This study highlights that innate immune responses can be affected by SARS-CoV-2 vaccination and fluctuate seasonally.

Nucleocapsid Antibodies as an Optimal Serological Marker of SARS-CoV-2 Infection: A Longitudinal Study at the Thomayer University Hospital

BACKGROUND

The longitudinal study was conducted over the initial 2 years of the COVID-19 pandemic, spanning from June 2020 to December 2022, in healthcare workers (HCWs) of the Thomayer University Hospital. A total of 3892 blood samples were collected and analyzed for total nucleocapsid (N) antibodies. The aim of the study was to evaluate the dynamics of N antibodies, their relationship to the PCR test, spike (S) antibodies, interferon-gamma, and prediction of reinfection with SARS-CoV-2.

METHODS

Blood collections were performed in three rounds, along with questionnaires addressing clinical symptoms of past infection, PCR testing, and vaccination. Antibody measurements included total N antibodies (Roche Diagnostics) and postvaccination S antibodies (Euroimmun). Cellular immunity was tested by interferon-gamma release assay (Euroimmun).

RESULTS

At the end of the study, 35.9% of HCWs were positive for N antibodies, and 39.5% of HCWs had either known PCR positivity or N antibodies or both. Ten percent of participants had no knowledge of a COVID-19 infection and 35% of positive individuals exhibited no symptoms. The values of positive antibodies decrease over a period of 6 months to 1 year, depending on the initial value, and their dynamics are highly variable. The study also demonstrated that the highest levels of spike antibodies and interferon-gamma occur during so-called hybrid immunity.

CONCLUSION

Nucleocapsid antibodies proved valuable in monitoring SARS-CoV-2 infection dynamics, and they may detect cases of SARS-CoV-2 infection missed by PCR tests. The study identified distinct patterns in antibody dynamics and protection of hybrid immunity during reinfection.

Rethinking Optimal Immunogens to Face SARS-CoV-2 Evolution Through Vaccination

SARS-CoV-2, which originated in China in late 2019, quickly fueled the global COVID-19 pandemic, profoundly impacting health and the economy worldwide. A series of vaccines, mostly based on the full SARS-CoV-2 Spike protein, were rapidly developed, showing excellent humoral and cellular responses and high efficacy against both symptomatic infection and severe disease. However, viral evolution and the waning humoral neutralizing responses strongly challenged vaccine long term effectiveness, mainly against symptomatic infection, making necessary a strategy of repeated and updated booster shots. In this repeated vaccination context, antibody repertoire diversification was evidenced, although immune imprinting after booster doses or reinfection was also demonstrated and identified as a major determinant of immunological responses to repeated antigen exposures. Considering that a small domain of the SARS-CoV-2 Spike protein, the receptor binding domain (RBD), is the major target of neutralizing antibodies and concentrates most viral mutations, the following text aims to provide insights into the ongoing debate over the best strategies for vaccine boosters. We address the relevance of developing new booster vaccines that target the evolving RBD, thus focusing on the relevant antigenic sites of the SARS-CoV-2 new variants. A combination of this strategy with immunofusing and computerized approaches could minimize immune imprinting, therefore optimizing neutralizing immune responses and booster vaccine efficacy.

Antibodies against SARS-CoV-2 spike protein in the cerebrospinal fluid of COVID-19 patients and vaccinated controls: a multicentre study

INTRODUCTION

SARS-CoV-2 antibodies in the cerebrospinal fluid (CSF) of COVID-19 patients possibly reflect blood-cerebrospinal fluid barrier (BCB) disruption due to systemic inflammation. However, some studies indicate that CSF antibodies signal a neurotropic infection. Currently, larger studies are needed to clarify this, and it is unknown if CSF antibodies appear solely after infection or also after COVID-19 vaccination. Therefore, we aimed to investigate the CSF dynamics of SARS-CoV-2 antibodies in a multicenter study of COVID-19 patients and vaccinated controls.

METHODS

A cohort study of Danish and Norwegian COVID-19 patients and controls investigated with a lumbar puncture (April 2020-December 2022). Serum and CSF were analysed locally for routine investigations, and centrally at Statens Serum Institut (Danish governmental public health institute) for SARS-CoV-2 IgG antibodies against the spike protein using the Euroimmun (quantitative) and Wantai (qualitative) assays. Primary outcome was the quantity of CSF SARS-CoV-2 antibodies post-COVID versus post-vaccination. Secondary outcomes included regression models examining the relationship between CSF antibodies and serum levels, albumin ratio, CSF pleocytosis, COVID-19 severity, and temporal antibody dynamics.

RESULTS

We included 124 individuals (Mean [SD] age 47.2 [16.6]; 59.7% males surviving COVID-19 and controls. Of these, 86 had paired CSF-serum testing. Antibody-index calculations did not support a SARS-CoV-2 brain infection. Multi-variate regression revealed that CSF SARS-CoV-2 antibodies were most strongly influenced by serum antibody levels and BCB permeability, as measured by increasing albumin ratio. CSF antibody levels displayed a dose-response relationship (p < 0.0001) influenced by preceding vaccinations or infections. CSF antibody levels (median [IQR]) were highest among those both previously infected and vaccinated, 100.0 [25.0-174.0], and those vaccinated without prior infection, 85.0 [12.0-142.0], and lowest among previously infected individuals without preceding vaccination, 5.9 [2.7-55.1], (p = 0.003). SARS-CoV-2 antibodies in CSF were also detected via qualitative assays in the COVID-19 (46.8%) and vaccinated (78.6%) groups, p = 0.03.

CONCLUSION

SARS-CoV-2 antibodies detected in CSF can be derived following both infection and vaccination for COVID-19. CSF antibody levels increase in a dose-response relationship with the number of prior infections and vaccinations and are most strongly influenced by serum antibody levels and BCB permeability. These findings stress the importance of carefully interpreting CSF antibody results when assessing neurological complications following infections not categorized as neurotropic.

Unraveling the impact of SARS-CoV-2 mutations on immunity: insights from innate immune recognition to antibody and T cell responses

Throughout the COVID-19 pandemic, the emergence of new viral variants has challenged public health efforts, often evading antibody responses generated by infections and vaccinations. This immune escape has led to waves of breakthrough infections, raising questions about the efficacy and durability of immune protection. Here we focus on the impact of SARS-CoV-2 Delta and Omicron spike mutations on ACE-2 receptor binding, protein stability, and immune response evasion. Delta and Omicron variants had 3-5 times higher binding affinities to ACE-2 than the ancestral strain (KDwt = 23.4 nM, KDDelta = 8.08 nM, KDBA.1 = 4.77 nM, KDBA.2 = 4.47 nM). The pattern recognition molecule mannose-binding lectin (MBL) has been shown to recognize the spike protein. Here we found that MBL binding remained largely unchanged across the variants, even after introducing mutations at single glycan sites. Although MBL binding decreased post-vaccination, it increased by 2.6-fold upon IgG depletion, suggesting a compensatory or redundant role in immune recognition. Notably, we identified two glycan sites (N717 and N801) as potentially essential for the structural integrity of the spike protein. We also evaluated the antibody and T cell responses. Neutralization by serum immunoglobulins was predominantly mediated by IgG rather than IgA and was markedly impaired against the Delta (5.8-fold decrease) and Omicron variants BA.1 (17.4-fold) and BA.2 (14.2-fold). T cell responses, initially conserved, waned rapidly within 3 months post-Omicron infection. Our data suggests that immune imprinting may have hindered antibody and T cell responses toward the variants. Overall, despite decreased antibody neutralization, MBL recognition and T cell responses were generally unaffected by the variants. These findings extend our understanding of the complex interplay between viral adaptation and immune response, underscoring the importance of considering MBL interactions, immune imprinting, and viral evolution dynamics in developing new vaccine and treatment strategies.

Tissue-resident memory T cells contribute to protection against heterologous SARS-CoV-2 challenge

New vaccine formulations are based on circulating strains of virus, which have tended to evolve to more readily transmit human to human and to evade the neutralizing antibody response. An assumption of this approach is that ancestral strains of virus will not recur. Recurrence of these strains could be a problem for individuals not previously exposed to ancestral spike protein. Here, we addressed this by infecting mice with recent SARS-CoV-2 variants and then challenging them with a highly pathogenic mouse-adapted virus closely related to the ancestral Wuhan-1 strain (SARS2-N501YMA30). We found that challenged mice were protected from severe disease, despite having low or no neutralizing antibodies against SARS2-N501YMA30. T cell depletion from previously infected mice did not diminish infection against clinical disease, although it resulted in delayed virus clearance in the nasal turbinate and, in some cases, in the lungs. Levels of tissue-resident memory T cells were significantly elevated in the nasal turbinate of previously infected mice compared with that of naive mice. However, this phenotype was not seen in lung tissues. Together, these results indicate that the immune response to newly circulating variants afforded protection against reinfection with the ancestral virus that was in part T cell based.

Evaluation of PLGA, lipid-PLGA hybrid nanoparticles, and cationic pH-sensitive liposomes as tuberculosis vaccine delivery systems in a Mycobacterium tuberculosis challenge mouse model - A comparison

Tuberculosis (TB) continues to pose a global threat for millennia, currently affecting over 2 billion people and causing 10.6 million new cases and 1.3 million deaths annually. The only existing vaccine, Mycobacterium Bovis Bacillus Calmette-Guérin (BCG), provides highly variable and inadequate protection in adults and adolescents. This study explores newly developed subunit tuberculosis vaccines that use a multistage protein fusion antigen Ag85b-ESAT6-Rv2034 (AER). The protection efficacy, as well as in vivo induced immune responses, were compared for five vaccines: BCG; AER-CpG/MPLA mix; poly(D,L-lactic-co-glycolic acid) (PLGA); lipid-PLGA hybrid nanoparticles (NPs); and cationic pH-sensitive liposomes (the latter three delivering AER together with CpG and MPLA). All vaccines, except the AER-adjuvant mix, induced protection in Mycobacterium tuberculosis (Mtb)-challenged C57/Bl6 mice as indicated by a significant reduction in bacterial burden in lungs and spleens of the animals. Four AER-based vaccines significantly increased the number of circulating multifunctional CD4+ and CD8+ T-cells producing IL-2, IFNγ, and TNFα, exhibiting a central memory phenotype. Furthermore, AER-based vaccines induced an increase in CD69+ B-cell counts as well as high antigen-specific antibody titers. Unexpectedly, none of the observed immune responses were associated with the bacterial burden outcome, such that the mechanism responsible for the observed vaccine-induced protection of these vaccines remains unclear. These findings suggest the existence of non-classical protective mechanisms for Mtb infection, which could, once identified, provide interesting targets for novel vaccines.

Anti-RBD IgG dynamics following infection or vaccination

Identifying parameters influencing SARS-CoV-2 antibody dynamics post infection or vaccination is crucial for refining vaccination strategies. In a longitudinal analysis of 1340 samples from 375 healthcare workers, we characterized peak serological response and IgG half-life. Peak antibody titers post 2 vaccine doses were ∼ 20 times higher than natural infection; conversely, infected individuals had extended antibody half-life. Clinical and demographical factors such as BMI, age and smoking shaped peak response without affecting anti-RBD IgG half-life. A third mRNA vaccine dose increased peak antibody titers and prolonged half-life compared to the second dose. These findings underscore the diverse kinetics of SARS-CoV-2 antibody responses, which is influenced by immunization type/number and clinical factors.

Comparison of different T cell assays for the retrospective determination of SARS-CoV-2 infection

It is important to be able to retrospectively determine severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infections with high accuracy, both for post-coronavirus disease 2019 (COVID-19) epidemiological studies, and to distinguish between Long COVID and other multi-syndromic diseases that have overlapping symptoms. Although serum antibody levels can be measured to retrospectively diagnose SARS-CoV-2 infections, peptide stimulation of memory T cell responses is a more sensitive approach. This is because robust memory T cells are generated after SARS-CoV-2 infection and persist even after antibodies wane below detectability thresholds. In this study, we compare T cell responses using FluoroSpot-based methods and overnight stimulation of whole blood with SARS-CoV-2 peptides followed by an ELISA. Both approaches have comparable sensitivity and specificity but require different equipment and samples to be used. Furthermore, the elimination of peptides that cross-react with other coronaviruses increases the assay specificity but trades off some sensitivity. Finally, this approach can be used on archival, cryopreserved PBMCs. This work shows comparative advantages for several methods to measure SARS-CoV-2 T cell responses that could be utilized by any laboratory studying the effects of the coronavirus disease 2019 pandemic.

SARS-CoV-2 Immunization Index in the Academic Community: A Retrospective Post-Vaccination Study

BACKGROUND/OBJECTIVES

The COVID-19 pandemic has revolutionized vaccine production and compelled a massive global vaccination campaign. This study aimed to estimate the positivity and levels of SARS-CoV-2 IgG antibodies acquired due to vaccination and infection in the academic population of a Portuguese university.

METHODS

Blood samples were collected and analyzed through the ELISA methodology, and statistical analysis was performed.

RESULTS

A total of 529 volunteers with at least one dose of the vaccine were enrolled in this study. Individuals without a prior COVID-19 diagnosis were divided into two groups: 350, who received a full vaccination, and 114, who received a full vaccination and a booster dose of the same vaccine (81) and mixed vaccines (33). Regarding the individuals who reported a prior SARS-CoV-2 infection, 31 received a full vaccination, and 34 received only one vaccination dose. Data analysis showed a higher level of IgG against SARS-CoV-2 in individuals who were younger, female, who received the Moderna vaccine, with recent post-vaccine administration, a mixed booster dose, and prior SARS-CoV-2 infection.

CONCLUSIONS

Assessing vaccination's effectiveness and group immunity is crucial for pandemic management, particularly in academic environments with high individual mobility, in order to define groups at risk and redirect infection control strategies.

Immunogenicity and Determinants of Antibody Response to the BNT162b2 mRNA Vaccine: A Longitudinal Study in a Cohort of People Living with HIV

BACKGROUND

The COVID-19 pandemic posed significant challenges worldwide, with SARS-CoV-2 vaccines critical in reducing morbidity and mortality. This study evaluates the immunogenicity and antibody persistence of the BNT162b2 vaccine in people living with HIV (PLWH).

METHODS

We monitored anti-SARS-CoV-2 Spike IgG concentration in a cohort of PLWH at five time points (T0-T4) using chemiluminescent microparticle immunoassays (CMIAs) at the baselined both during and after vaccination. In severely immunocompromised individuals, a boosting dose was recommended, and participants and IgG concentration were measured in the two subgroups (boosted and not boosted).

RESULTS

In total, 165 PLWH were included, and 83% were male with a median age of 55 years (IQR: 47-62). At T1, 161 participants (97.6%) showed seroconversion with a median of IgG values of 468.8 AU/mL (IQR: 200.4-774.3 AU/mL). By T2, all subjects maintained a positive result, with the median anti-SARS-CoV-2 Spike IgG concentration increasing to 6191.6 AU/mL (IQR: 3666.7-10,800.8 AU/mL). At T3, all participants kept their antibody levels above the positivity threshold with a median of 1694.3 AU/mL (IQR: 926.3-2966.4 AU/mL). At T4, those without a booster dose exhibited a marked decrease to a median of 649.1 AU/mL (IQR: 425.5-1299.8 AU/mL), whereas those with a booster experienced a significant increase to a median of 13,105.2 AU/mL (IQR: 9187.5-18,552.1 AU/mL). The immune response was negatively influenced by the presence of dyslipidaemia at T1 (aOR 4.75, 95% CI: 1.39-16.20) and diabetes at T3 (aOR 7.11, 95% CI: 1.10-46.1), while the use of protease inhibitors (aORs 0.06, 95% CI: 0.01-0.91) and being female (aOR 0.02, 95% CI: 0.01-0.32) at T3 were protective factors.

CONCLUSIONS

The immunogenicity of the BNT162b2 vaccine in PLWH has been confirmed, with booster doses necessary to maintain high levels of anti-SARS-CoV-2 Spike IgG antibodies, especially in patients with comorbidities. These findings underline the importance of a personalized vaccination strategy in this population.

Vaccine responses and hybrid immunity in people living with HIV after SARS-CoV-2 breakthrough infections

The COVID-19 pandemic posed a challenge for people living with HIV (PLWH), particularly immune non-responders (INR) with compromised CD4 T-cell reconstitution following antiretroviral therapy (CD4 count <350 cells per mm3). Their diminished vaccine responses raised concerns about their vulnerability to SARS-CoV-2 breakthrough infections (BTI). Our in-depth study here revealed chronic inflammation in PLWH and a limited anti-Spike IgG response after vaccination in INR. Nevertheless, the imprinting of Spike-specific B cells by vaccination significantly enhanced the humoral responses after BTI. Notably, the magnitude of cellular CD4 response in all PLWH was comparable to that in healthy donors (HD). However, the polyfunctionality and phenotype of Spike-specific CD8 T cells in INR differed from controls. The findings highlight the need for additional boosters with variant vaccines, and for monitoring ART adherence and the durability of both humoral and cellular anti-SARS-CoV-2 immunity in INR.

A Population-Based Study of SARS-CoV-2 IgG Antibody Responses to Vaccination in Manitoba

Understanding variables that influence antibody responses to COVID-19 vaccination within a population can provide valuable information on future vaccination strategies. In this population-based study, we examined the antibody responses to COVID-19 vaccination in Manitoba using residual serum specimens collected between January 2021 and March 2022 (n = 20,365). Samples were tested for spike and nucleocapsid IgG against SARS-CoV-2 using clinically validated assays. We assessed the impacts of multiple factors on post-vaccination antibody titres including type of vaccine, age, sex, geographic location, number of doses received, and timing of vaccination. Our investigation demonstrated that vaccination with one dose of Moderna mRNA-1273 elicited higher anti-spike IgG titres overall compared to Pfizer BNT162b2 vaccination, while one dose of Pfizer BNT162b2 followed by a second dose of Moderna mRNA-1273 exhibited higher titres than two doses of Pfizer BNT162b2 or Moderna mRNA-1273, irrespective of age. Age and time post-vaccination had considerable effects on antibody responses, with older age groups exhibiting lower anti-spike IgG titres than younger ages, and titres of those vaccinated with Pfizer BNT162b2 waning faster than those vaccinated with Moderna mRNA-1273 or a combination of Pfizer BNT162b2 and Moderna mRNA-1273. Antibody titres did not appear to be affected by sex or geographic location. Our results identify how factors such as age and type of vaccine can influence antibody responses to vaccination, and how antibody titres wane over time. This information highlights the importance of tailoring vaccine regimens to specific populations, especially those at increased risk of severe COVID-19 and can be used to inform future vaccination strategies, scheduling of booster doses, and public health measures.

Robust immune response to COVID-19 vaccination in the island population of Greenland

BACKGROUND

In Greenland, the COVID-19 pandemic was characterised by a late onset of community transmission and a low impact on the healthcare system, hypothesised as being partly due to a high uptake of vaccinations. To underpin this description, we aimed to assess the SARS-CoV-2 immune response post-vaccination in a Greenlandic population.

METHODS

In this observational cohort study, we included 430 adults in Greenland who had received a complete two-dose SARS-CoV-2 vaccination at enrolment. The total plasma SARS-CoV-2 spike glycoprotein Ig antibodies (S-Ab) induced by either the BNT162b2 or mRNA-1273 vaccine, was measured up to 11 months after the second vaccine dose. In addition, total salivary S-Abs were examined in 107 participants, and the T-cell response to the spike glycoprotein was assessed in 78 participants out of the entire study cohort.

RESULTS

Here we demonstrate that two months after the second vaccine dose, 96% of participants have protective plasma S-Ab levels. By 11 months, 98% have protective levels, with prior SARS-CoV-2 infection particularly enhancing S-Ab levels by 37% (95% CI 25-51%). Among individuals aged 60 years and older, we observe a 21% (95% CI 7-33%) reduction in antibody response. Total salivary S-Ab levels are detectable in all participants and significantly correlate with plasma levels. Moreover, all participants exhibit a robust SARS-CoV-2-specific T-cell response 11 months post-primary vaccination.

CONCLUSIONS

Our findings show that Greenlanders exhibit a robust and lasting immune response, both humoral and cellular, comparable to other population groups up to at least 11 months after the second vaccine dose. These results corroborate the hypothesis that vaccines contributed to the mild impact of the COVID-19 pandemic in the Greenlandic population.

Development of antibody levels and subsequent decline in individuals with vaccine induced and hybrid immunity to SARS-CoV-2

OBJECTIVES

This study aimed to compare antibody trajectories among individuals with SARS-CoV-2 hybrid and vaccine-induced immunity.

METHODS

Danish adults receiving three doses of BTN162b2 or mRNA-1237 were included prior to first vaccination (Day 0). SARS-CoV-2 anti-spike IgG levels were assessed before each vaccine dose, at Day 90, Day 180, 28 days after 3rd vaccination (Day 251), Day 365, and prior to 4th vaccination (Day 535). SARS-CoV-2 PCR results were extracted from the national microbiology database. Mixed-effect multivariable linear regression investigated the impact of hybrid-immunity (stratified into 4 groups: no hybrid immunity, PCR+ prior to 3rd dose, PCR+ after 3rd dose and before Day 365, PCR+ after Day 365) on anti-spike IgG trajectories.

RESULTS

A total of 4,936 individuals were included, 47% developed hybrid-immunity. Anti-spike IgG increases were observed in all groups at Day 251, with the highest levels in those PCR+ prior to 3rd dose (Geometric Mean; 535,647AU/mL vs. 374,665AU/mL with no hybrid-immunity, P<0.0001). Further increases were observed in participants who developed hybrid immunity after their 3rd dose. Anti-spike IgG levels declined from Day 251-535 in individuals without hybrid-immunity and in those who developed hybrid-immunity prior to their 3rd dose, with lower rate of decline in those with hybrid-immunity.

CONCLUSION

Hybrid-immunity results in higher and more durable antibody trajectories in vaccinated individuals.

Modeling of anti-spike IgG and neutralizing antibody waning after anti-SARS-CoV-2 mRNA vaccination

At present, mRNA-based vaccines against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) are being administered on a global scale. While the efficacy of mRNA vaccines has been demonstrated, several unknowns remains. For example, as the number of booster vaccinations increases, there are uncertainties regarding how long effects of a vaccine will last and how much individual variability exists. In this study, to predict the duration of vaccine efficacy, we modeled the kinetics of antibody levels for each SARS-CoV-2 vaccination dose, incorporating predictive intervals to estimate the duration of vaccine efficacy and to account for variability among individuals. A total of 3,059 serum samples from 1,346 participants were assayed to quantify IgG antibodies specific for the S1 subunit of the S protein (anti-S1 IgG) and neutralizing antibody activities against SARS-CoV-2. A power law model was used to simulate the decay of antibody titers following vaccination, and models were constructed to assess antibody level kinetics after the second, third, fourth, and fifth vaccinations. The models assumed that booster vaccinations would significantly reduce the decline in anti-S antibody and neutralizing antibody levels, resulting in levels being maintained for a longer period. No significant differences in the decay rate of antibody levels were observed among age groups, yet the peak titers of antibody levels were significantly higher in the ≤ 39 age group than in the ≥ 60 age group following the second vaccination; these differences were not observed after the third and fourth vaccinations. The modeling of antibody level kinetics after vaccination is considered to be useful for understanding the immune status of mRNA vaccine recipients.

Dynamics of anti-SARS-CoV-2 IgG antibody responses following breakthrough infection and the predicted protective efficacy: A longitudinal community-based population study in China

OBJECTIVES

To assess the dynamics of the anti-SARS-CoV-2 IgG antibody levels and their efficacy against COVID-19.

METHODS

We conducted a longitudinal serological analysis of 852 breakthrough COVID-19 infections among the community-based population in Yichang, China. Anti-SARS-CoV-2 IgG levels were measured by chemiluminescence at approximately 3, 4, and 9 months after infection. A linear mixed model predicted IgG antibody decline over 18 months. The effectiveness of antibodies in preventing symptomatic and severe infections was determined using an existing meta-regression model.

RESULTS

IgG antibodies slowly declined after breakthrough infections. Initially high at around 3 months (339.44 AU/mL, IQR: 262.78-382.95 AU/mL), levels remained significant at 9 months (297.74 AU/mL, IQR: 213.22-360.62 AU/mL). The elderly (≥60 years) had lower antibody levels compared to the young (<20 years) (P < 0.001). The protective efficacy of antibodies against symptomatic and severe infections was lower in the elderly (≥60 years) (78.34% and 86.33%) compared to the young (<20 years) (96.56% and 98.75%) after 1 year.

CONCLUSION

The study indicated a slow decline in anti-SARS-CoV-2 IgG antibodies, maintaining considerable efficacy for over 1 year. However, lower levels in the elderly suggest reduced protective effects, underscoring the need for age-specific vaccination strategies.

Prioritising older individuals for COVID-19 booster vaccination leads to optimal public health outcomes in a range of socio-economic settings

The rapid development of vaccines against SARS-CoV-2 altered the course of the COVID-19 pandemic. In most countries, vaccinations were initially targeted at high-risk populations, including older individuals and healthcare workers. Now, despite substantial infection- and vaccine-induced immunity in host populations worldwide, waning immunity and the emergence of novel variants continue to cause significant waves of infection and disease. Policy makers must determine how to deploy booster vaccinations, particularly when constraints in vaccine supply, delivery and cost mean that booster vaccines cannot be administered to everyone. A key question is therefore whether older individuals should again be prioritised for vaccination, or whether alternative strategies (e.g. offering booster vaccines to the individuals who have most contacts with others and therefore drive infection) can instead offer indirect protection to older individuals. Here, we use mathematical modelling to address this question, considering SARS-CoV-2 transmission in a range of countries with different socio-economic backgrounds. We show that the population structures of different countries can have a pronounced effect on the impact of booster vaccination, even when identical booster vaccination targeting strategies are adopted. However, under the assumed transmission model, prioritising older individuals for booster vaccination consistently leads to the most favourable public health outcomes in every setting considered. This remains true for a range of assumptions about booster vaccine supply and timing, and for different assumed policy objectives of booster vaccination.

A Dynamic Prognostic Model for Identifying Vulnerable COVID-19 Patients at High Risk of Rapid Deterioration

PURPOSE

We aimed to validate and, if performance was unsatisfactory, update the previously published prognostic model to predict clinical deterioration in patients hospitalized for COVID-19, using data following vaccine availability.

METHODS

Using electronic health records of patients ≥18 years, with laboratory-confirmed COVID-19, from a large care-delivery network in Massachusetts, USA, from March 2020 to November 2021, we tested the performance of the previously developed prediction model and updated the prediction model by incorporating data after availability of COVID-19 vaccines. We randomly divided data into development (70%) and validation (30%) cohorts. We built a model predicting worsening in a published severity scale in 24 h by LASSO regression and evaluated performance by c-statistic and Brier score.

RESULTS

Our study cohort consisted of 8185 patients (Development: 5730 patients [mean age: 62; 44% female] and Validation: 2455 patients [mean age: 62; 45% female]). The previously published model had suboptimal performance using data after November 2020 (N = 4973, c-statistic = 0.60. Brier score = 0.11). After retraining with the new data, the updated model included 38 predictors including 18 changing biomarkers. Patients hospitalized after Jun 1st, 2021 (when COVID-19 vaccines became widely available in Massachusetts) were younger and had fewer comorbidities than those hospitalized before. The c-statistic and Brier score were 0.77 and 0.13 in the development cohort, and 0.73 and 0.14 in the validation cohort.

CONCLUSION

The characteristics of patients hospitalized for COVID-19 differed substantially over time. We developed a new dynamic model for rapid progression with satisfactory performance in the validation set.

Inducing Long Lasting B Cell and T Cell Immunity Against Multiple Variants of SARS-CoV-2 Through Mutant Bacteriophage Qβ-Receptor Binding Domain Conjugate

More than 3 years into the global pandemic, the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) remains a significant threat to public health. Immunities acquired from infection or current vaccines fail to provide long term protection against subsequent infections, mainly due to their fast-waning nature and the emergence of variants of concerns (VOCs) such as Omicron. To overcome these limitations, SARS-CoV-2 Spike protein receptor binding domain (RBD)-based epitopes are investigated as conjugates with a powerful carrier, the mutant bacteriophage Qβ (mQβ). The epitope design is critical to eliciting potent antibody responses with the full length RBD being superior to peptide and glycopeptide antigens. The full length RBD conjugated with mQβ activates both humoral and cellular immune systems in vivo, inducing broad spectrum, persistent, and comprehensive immune responses effective against multiple VOCs including Delta and Omicron variants, rendering it a promising vaccine candidate.

SARS-CoV-2 anti-RBD and anti-N protein responses are differentially regulated between mother-child pairs: insight from a national study cohort at the Faroe Islands

Background

Knowledge about SARS-CoV-2 antibody dynamics in neonates and direct comparisons with maternal antibody responses are not well established. This study aimed to characterize and directly compare the maternal and infant antibody response in a national birth cohort from the Faroe Islands.

Methods

The levels of immunoglobulins (Ig) targeting the receptor binding domain (RBD) of the spike protein and the nucleocapsid protein (N protein) of SARS-CoV-2 were investigated in maternal blood and umbilical cord blood from neonates. The study included 537 neonates and 565 mothers from the Faroe Islands, and follow-up samples were collected 12 months after birth. Multiple linear regression models were used to assess associations of maternal parameters with maternal and neonatal Ig levels and pregnancy outcomes.

Results

The finding showed that neonates acquired varying levels of SARS-CoV-2 antibodies through transplacental transfer, and the levels were significantly influenced by the mother's vaccination and infection status. The study also found that maternal vaccination and the presence of SARS-CoV-2 antibodies targeting spike RBD were associated with gestational age and APGAR scores. Furthermore, the anti-RBD and -N protein-specific antibody response dynamics during 12 months after birth exhibited differences between mothers and children. RBD and N protein responses were maintained at follow-up in the mother's cohort, while only the N protein response was maintained at follow-up in the children's cohort.

Conclusion

In conclusion, SARS-CoV-2-specific immune responses in newborns rely on maternal immunity, while the persistence of SARS-CoV-2-specific Igs appears to be differently regulated between mothers and children. The study provides new insights into the dynamics of SARS-CoV-2-specific immune responses in newborns and underscores the nuanced relationship between maternal factors and neonatal humoral responses.

Durability of immunity and clinical protection in nursing home residents following bivalent SARS-CoV-2 vaccination

BACKGROUND

Bivalent SARS-CoV-2 vaccines were developed to counter increasing susceptibility to emerging SARS-CoV-2 variants. We evaluated the durability of immunity and protection following first bivalent vaccination among nursing home residents.

METHODS

We evaluated anti-spike and neutralization titers from blood in 653 community nursing home residents before and after each monovalent booster, and a bivalent vaccine. Concurrent clinical outcomes were evaluated using electronic health record data from a separate cohort of 3783 residents of Veterans Affairs (VA) nursing homes who had received at least the primary series monovalent vaccination. Using target trial emulation, we compared VA residents who did and did not receive the bivalent vaccine to measure vaccine effectiveness against infection, hospitalization, and death.

FINDINGS

In the community cohort, Omicron BA.5 neutralization activity rose after each monovalent and bivalent booster vaccination regardless of prior infection history. Titers declined over time but six months post-bivalent vaccination, BA.5 neutralization persisted at detectable levels in 75% of infection-naive and 98% of prior-infected individuals. In the VA nursing home cohort, bivalent vaccine added effectiveness to monovalent booster vaccination by 18.5% for infection (95% confidence interval (CI) -5.6, 34.0%), and 29.2% for hospitalization or death (95% CI -14.2, 56.2%) over five months.

INTERPRETATION

The level of protection declined after bivalent vaccination over a 6 month period and may open a window of added vulnerability before the next updated vaccine becomes available, suggesting a subset of nursing home residents may benefit from an additional vaccination booster.

FUNDING

CDC, NIH, VHA.

SIRS epidemics with individual heterogeneity of immunity waning

In the current paper we analyse an extended SIRS epidemic model in which immunity at the individual level wanes gradually at exponential rate, but where the waning rate may differ between individuals, for instance as an effect of differences in immune systems. The model also includes vaccination schemes aimed to reach and maintain herd immunity. We consider both the informed situation where the individual waning parameters are known, thus allowing selection of vaccinees being based on both time since last vaccination as well as on the individual waning rate, and the more likely uninformed situation where individual waning parameters are unobserved, thus only allowing vaccination schemes to depend on time since last vaccination. The optimal vaccination policies for both the informed and uniformed heterogeneous situation are derived and compared with the homogeneous waning model (meaning all individuals have the same immunity waning rate), as well as to the classic SIRS model where immunity at the individual level drops from complete immunity to complete susceptibility in one leap. It is shown that the classic SIRS model requires least vaccines, followed by the SIRS with homogeneous gradual waning, followed by the informed situation for the model with heterogeneous gradual waning. The situation requiring most vaccines for herd immunity is the most likely scenario, that immunity wanes gradually with unobserved individual heterogeneity. For parameter values chosen to mimic COVID-19 and assuming perfect initial immunity and cumulative immunity of 12 months, the classic homogeneous SIRS epidemic suggests that vaccinating individuals every 15 months is sufficient to reach and maintain herd immunity, whereas the uninformed case for exponential waning with rate heterogeneity corresponding to a coefficient of variation being 0.5, requires that individuals instead need to be vaccinated every 4.4 months.

The Impact of Time between Booster Doses on Humoral Immune Response in Solid Organ Transplant Recipients Vaccinated with BNT162b2 Vaccines

As solid organ transplant (SOT) recipients remain at risk of severe outcomes after SARS-CoV-2 infections, vaccination continues to be an important preventive measure. In SOT recipients previously vaccinated with at least three doses of BNT162b2, we investigated humoral responses to BNT162b2 booster doses. Anti-SARS-CoV-2 receptor binding domain (RBD) immunoglobulin G (IgG) was measured using an in-house ELISA. Linear mixed models were fitted to investigate the change in the geometric mean concentration (GMC) of anti-SARS-CoV-2 RBD IgG after vaccination in participants with intervals of more or less than six months between the last two doses of vaccine. We included 107 SOT recipients vaccinated with a BNT162b2 vaccine. In participants with an interval of more than six months between the last two vaccine doses, we found a 1.34-fold change in GMC per month (95% CI 1.25-1.44), while we found a 1.09-fold change in GMC per month (95% CI 0.89-1.34) in participants with an interval of less than six months between the last two vaccine doses, resulting in a rate ratio of 0.82 (95% CI 0.66 to 1.01, p = 0.063). In conclusion, the administration of identical COVID-19 mRNA vaccine boosters within six months to SOT recipients may result in limited humoral immunogenicity of the last dose.

Modeling and predicting individual variation in COVID-19 vaccine-elicited antibody response in the general population

As we learned during the COVID-19 pandemic, vaccines are one of the most important tools in infectious disease control. To date, an unprecedentedly large volume of high-quality data on COVID-19 vaccinations have been accumulated. For preparedness in future pandemics beyond COVID-19, these valuable datasets should be analyzed to best shape an effective vaccination strategy. We are collecting longitudinal data from a community-based cohort in Fukushima, Japan, that consists of 2,407 individuals who underwent serum sampling two or three times after a two-dose vaccination with either BNT162b2 or mRNA-1273. Using the individually reconstructed time courses of the vaccine-elicited antibody response based on mathematical modeling, we first identified basic demographic and health information that contributed to the main features of the antibody dynamics, i.e., the peak, the duration, and the area under the curve. We showed that these three features of antibody dynamics were partially explained by underlying medical conditions, adverse reactions to vaccinations, and medications, consistent with the findings of previous studies. We then applied to these factors a recently proposed computational method to optimally fit an "antibody score", which resulted in an integer-based score that can be used as a basis for identifying individuals with higher or lower antibody titers from basic demographic and health information. The score can be easily calculated by individuals themselves or by medical practitioners. Although the sensitivity of this score is currently not very high, in the future, as more data become available, it has the potential to identify vulnerable populations and encourage them to get booster vaccinations. Our mathematical model can be extended to any kind of vaccination and therefore can form a basis for policy decisions regarding the distribution of booster vaccines to strengthen immunity in future pandemics.

Impact of Prior COVID-19 Immunization and/or Prior Infection on Immune Responses and Clinical Outcomes

Cellular and humoral immunity exhibit dynamic adaptation to the mutating SARS-CoV-2 virus. It is noteworthy that immune responses differ significantly, influenced by whether a patient has received vaccination or whether there is co-occurrence of naturally acquired and vaccine-induced immunity, known as hybrid immunity. The different immune reactions, conditional on vaccination status and the viral variant involved, bear implications for inflammatory responses, patient outcomes, pathogen transmission rates, and lingering post-COVID conditions. Considering these developments, we have performed a review of recently published literature, aiming to disentangle the intricate relationships among immunological profiles, transmission, the long-term health effects post-COVID infection poses, and the resultant clinical manifestations. This investigation is directed toward understanding the variability in the longevity and potency of cellular and humoral immune responses elicited by immunization and hybrid infection.

SARS-CoV-2 booster vaccine dose significantly extends humoral immune response half-life beyond the primary series

SARS-CoV-2 lipid nanoparticle mRNA vaccines continue to be administered as the predominant prophylactic measure to reduce COVID-19 disease pathogenesis. Quantifying the kinetics of the secondary immune response from subsequent doses beyond the primary series and understanding how dose-dependent immune waning kinetics vary as a function of age, sex, and various comorbidities remains an important question. We study anti-spike IgG waning kinetics in 152 individuals who received an mRNA-based primary series (first two doses) and a subset of 137 individuals who then received an mRNA-based booster dose. We find the booster dose elicits a 71-84% increase in the median Anti-S half life over that of the primary series. We find the Anti-S half life for both primary series and booster doses decreases with age. However, we stress that although chronological age continues to be a good proxy for vaccine-induced humoral waning, immunosenescence is likely not the mechanism, rather, more likely the mechanism is related to the presence of noncommunicable diseases, which also accumulate with age, that affect immune regulation. We are able to independently reproduce recent observations that those with pre-existing asthma exhibit a stronger primary series humoral response to vaccination than compared to those that do not, and further, we find this result is sustained for the booster dose. Finally, via a single-variate Kruskal-Wallis test we find no difference between male and female humoral decay kinetics, however, a multivariate approach utilizing  Least Absolute Shrinkage and Selection Operator (LASSO) regression for feature selection reveals a statistically significant (p < 1 × 10 - 3 ), albeit small, bias in favour of longer-lasting humoral immunity amongst males.

Vaccination impairs de novo immune response to omicron breakthrough infection, a precondition for the original antigenic sin

Several studies have suggested the imprinting of SARS-CoV-2 immunity by original immune challenge without addressing the formation of the de novo response to successive antigen exposures. As this is crucial for the development of the original antigenic sin, we assessed the immune response against the mutated epitopes of omicron SARS-CoV-2 after vaccine breakthrough. Our data demonstrate a robust humoral response in thrice-vaccinated individuals following omicron breakthrough which is a recall of vaccine-induced memory. The humoral and memory B cell responses against the altered regions of the omicron surface proteins are impaired. The T cell responses to mutated epitopes of the omicron spike protein are present due to the high cross-reactivity of vaccine-induced T cells rather than the formation of a de novo response. Our findings, therefore, underpin the speculation that the imprinting of SARS-CoV-2 immunity by vaccination may lead to the development of original antigenic sin if future variants overcome the vaccine-induced immunity.

Neutralizing antibody and CD8+ T cell responses following BA.4/5 bivalent COVID-19 booster vaccination in adults with and without prior exposure to SARS-CoV-2

As severe acute respiratory coronavirus 2 (SARS-CoV-2) variants continue to emerge, it is important to characterize immune responses against variants which can inform on protection efficacies following booster vaccination. In this study, neutralizing breadth and antigen-specific CD8+ T cell responses were analyzed in both infection-naïve and infection-experienced individuals following administration of a booster bivalent Wuhan-Hu-1+BA.4/5 Comirnaty® mRNA vaccine. Significantly higher neutralizing titers were found after this vaccination compared to the pre-third booster vaccination time point. Further, neutralizing breadth to omicron variants, including BA.1, BA.2, BA.5, BQ.1 and XBB.1, was found to be boosted following bivalent vaccination. SARS-CoV-2-specific CD8+ T cells were identified, but with no evidence that frequencies were increased following booster vaccinations. Spike protein-specific CD8+ T cells were the only responses detected after vaccination and non-spike-specific CD8+ T cells were only detected after infection. Both spike-specific and non-spike-specific CD8+ T cells were found at much lower frequencies than CD8+ T cells specific to cytomegalovirus (CMV), Epstein-Barr virus (EBV) and influenza (Flu). Taken together, these results show that the bivalent Wuhan-Hu-1+BA.4/5 Comirnaty® mRNA vaccine boosted the breadth of neutralization to newer SARS-CoV-2 variants and that vaccination is able to induce spike protein-specific CD8+ T cell responses, which are maintained longitudinally.

Vaccine effects on COVID-19 infection with bivalent boosting by age group

This paper examines time-series vaccine effectiveness on COVID-19 infection with/without a bivalent booster dose by 6 age groups such as 18-29, 30-49, 50-64, 65-79, 80+, and all_ages respectively. CDC's COVID data on rates of COVID-19 cases and deaths by updated (bivalent) booster status was used in this study. This result concludes that there is no difference between vaccines with or without a bivalent booster dose for preventing COVID-19 infection in 6 age groups 18-29, 30-49, 50-64, 65-79, 80+, and all_ages. Vaccination is effective in two age groups of 65-79 and 80+ for preventing COVID-19 infection. However, vaccine effectiveness against COVID-19 infection has not been confirmed in the 18-29 and 30-49 age groups.

Low antibody levels associated with significantly increased rate of SARS-CoV-2 infection in a highly vaccinated population from the US National Basketball Association

SARS-CoV-2 antibody levels may serve as a correlate for immunity and could inform optimal booster timing. The relationship between antibody levels and protection from infection was evaluated in vaccinated individuals from the US National Basketball Association who had antibody levels measured at a single time point from September 12, 2021, to December 31, 2021. Cox proportional hazards models were used to estimate the risk of infection within 90 days of serologic testing by antibody level (<250, 250-800, and >800 AU/mL1 ), adjusting for age, time since last vaccine dose, and history of SARS-CoV-2 infection. Individuals were censored on date of booster receipt. The analytic cohort comprised 2323 individuals and was 78.2% male, 68.1% aged ≤40 years, and 56.4% vaccinated (primary series) with the Pfizer-BioNTech mRNA vaccine. Among the 2248 (96.8%) individuals not yet boosted at antibody testing, 77% completed their primary vaccine series 4-6 months before testing and the median (interquartile range) antibody level was 293.5 (interquartile range: 121.0-740.5) AU/mL. Those with levels <250 AU/mL (adj hazard ratio [HR]: 2.4; 95% confidence interval [CI]: 1.5-3.7) and 250-800 AU/mL (adj HR: 1.5; 95% CI: 0.98-2.4) had greater infection risk compared to those with levels >800 AU/mL. Antibody levels could inform individual COVID-19 risk and booster scheduling.

Demographic and Clinical Factors Associated With SARS-CoV-2 Spike 1 Antibody Response Among Vaccinated US Adults: the C4R Study

This study investigates correlates of anti-S1 antibody response following COVID-19 vaccination in a U.S. population-based meta-cohort of adults participating in longstanding NIH-funded cohort studies. Anti-S1 antibodies were measured from dried blood spots collected between February 2021-August 2022 using Luminex-based microsphere immunoassays. Of 6245 participants, mean age was 73 years (range, 21-100), 58% were female, and 76% were non-Hispanic White. Nearly 52% of participants received the BNT162b2 vaccine and 48% received the mRNA-1273 vaccine. Lower anti-S1 antibody levels are associated with age of 65 years or older, male sex, higher body mass index, smoking, diabetes, COPD and receipt of BNT16b2 vaccine (vs mRNA-1273). Participants with a prior infection, particularly those with a history of hospitalized illness, have higher anti-S1 antibody levels. These results suggest that adults with certain socio-demographic and clinical characteristics may have less robust antibody responses to COVID-19 vaccination and could be prioritized for more frequent re-vaccination.

Creation of a pandemic memory by tracing COVID-19 infections and immunity in Luxembourg (CON-VINCE)

BACKGROUND

During the COVID-19 pandemic swift implementation of research cohorts was key. While many studies focused exclusively on infected individuals, population based cohorts are essential for the follow-up of SARS-CoV-2 impact on public health. Here we present the CON-VINCE cohort, estimate the point and period prevalence of the SARS-CoV-2 infection, reflect on the spread within the Luxembourgish population, examine immune responses to SARS-CoV-2 infection and vaccination, and ascertain the impact of the pandemic on population psychological wellbeing at a nationwide level.

METHODS

A representative sample of the adult Luxembourgish population was enrolled. The cohort was followed-up for twelve months. SARS-CoV-2 RT-qPCR and serology were conducted at each sampling visit. The surveys included detailed epidemiological, clinical, socio-economic, and psychological data.

RESULTS

One thousand eight hundred sixty-five individuals were followed over seven visits (April 2020-June 2021) with the final weighted period prevalence of SARS-CoV-2 infection of 15%. The participants had similar risks of being infected regardless of their gender, age, employment status and education level. Vaccination increased the chances of IgG-S positivity in infected individuals. Depression, anxiety, loneliness and stress levels increased at a point of study when there were strict containment measures, returning to baseline afterwards.

CONCLUSION

The data collected in CON-VINCE study allowed obtaining insights into the infection spread in Luxembourg, immunity build-up and the impact of the pandemic on psychological wellbeing of the population. Moreover, the study holds great translational potential, as samples stored at the biobank, together with self-reported questionnaire information, can be exploited in further research.

TRIAL REGISTRATION

Trial registration number: NCT04379297, 10 April 2020.

"Every Time It Comes Time for Another Shot, It's a Re-Evaluation": A Qualitative Study of Intent to Receive COVID-19 Boosters among Parents Who Were Hesitant Adopters of the COVID-19 Vaccine

COVID-19 vaccine coverage remains low for US children, especially among those living in rural areas and the Southern/Southeastern US. As of 12 September 2023, the CDC recommended bivalent booster doses for everyone 6 months and older. Emerging research has shown an individual may be vaccine hesitant and also choose to receive a vaccine for themselves or their child(ren); however, little is known regarding how hesitant adopters evaluate COVID-19 booster vaccinations. We used an exploratory qualitative descriptive study design and conducted individual interviews with COVID-19 vaccine-hesitant adopter parents (n = 20) to explore COVID-19 parental intentions to have children receive COVID-19 boosters. Three primary themes emerged during the analysis: risk, confidence, and intent, with risk assessments from COVID-19 and COVID-19 vaccine confidence often related to an individual parent's intent to vaccinate. We also found links among individuals with persistent concerns about the COVID-19 vaccine and low COVID-19 vaccine confidence with conditional and/or low/no intent and refusal to receive recommended boosters for children. Our findings suggest that healthcare providers and public health officials should continue making strong recommendations for vaccines, continue to address parental concerns, and provide strong evidence for vaccine safety and efficacy even among the vaccinated.

Enhancing Immunological Memory: Unveiling Booster Doses to Bolster Vaccine Efficacy Against Evolving SARS-CoV-2 Mutant Variants

A growing number of re-infections with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in previously immunized individuals has sparked discussions about the potential need for a booster vaccine dosage to counteract declining antibody levels and new strains. The protective immunity produced by vaccinations, and past illnesses relies on immunological memory. CD4 + T cells, CD8 + T cells, B cells, and long-lasting antibody responses are all components of the adaptive immune system that can generate and maintain this immunological memory. Since novel mutant variants have emerged one after the other, the world has been hit by repeated waves. Various vaccine formulations against SARS-CoV-2 have been administered across the globe. Thus, estimating the efficacy of those vaccines against gradually developed mutant stains is the essential parameter regarding the fate of those vaccine formulations and the necessity of booster doses and their frequency. In this review, focus has also been given to how vaccination stacks up against moderate and severe acute infections in terms of the longevity of the immune cells, neutralizing antibody responses, etc. However, hybrid immunity shows a greater accuracy of re-infection of variants of concern (VOCs) of SARS-CoV-2 than infection and immunization. The review conveys knowledge of detailed information about several marketed vaccines and the status of their efficacy against specific mutant strains of SARS-CoV-2. Furthermore, this review discusses the status of immunological memory after infection, mixed infection, and vaccination.

The immune response to SARS-CoV-2 in people with HIV

This review examines the intersection of the HIV and SARS-CoV-2 pandemics. People with HIV (PWH) are a heterogeneous group that differ in their degree of immune suppression, immune reconstitution, and viral control. While COVID-19 in those with well-controlled HIV infection poses no greater risk than that for HIV-uninfected individuals, people with advanced HIV disease are more vulnerable to poor COVID-19 outcomes. COVID-19 vaccines are effective and well tolerated in the majority of PWH, though reduced vaccine efficacy, breakthrough infections and faster waning of vaccine effectiveness have been demonstrated in PWH. This is likely a result of suboptimal humoral and cellular immune responses after vaccination. People with advanced HIV may also experience prolonged infection that may give rise to new epidemiologically significant variants, but initiation or resumption of antiretroviral therapy (ART) can effectively clear persistent infection. COVID-19 vaccine guidelines reflect these increased risks and recommend prioritization for vaccination and additional booster doses for PWH who are moderately to severely immunocompromised. We recommend continued research and monitoring of PWH with SARS-CoV-2 infection, especially in areas with a high HIV burden.

Sustained S-IgG and S-IgA antibodies to Moderna's mRNA-1273 vaccine in a Sub-Saharan African cohort suggests need for booster timing reconsiderations

Introduction

This study sought to elucidate the long-term antibody responses to the Moderna mRNA-1273 COVID-19 vaccine within a Ugandan cohort, aiming to contribute to the sparse data on m-RNA vaccine immunogenicity in Sub-Saharan Africa.

Methods

We tracked the development and persistence of the elicited antibodies in 19 participants aged 18 to 67, who received two doses of the mRNA-1273 vaccine. A validated enzyme-linked immunosorbent assay (ELISA) was used to quantify SARS-CoV-2-specific IgG, IgM, and IgA antibodies against the spike (S) and nucleoproteins (N). The study's temporal scope extended from the baseline to one year, capturing immediate and long-term immune responses. Statistical analyses were performed using the Wilcoxon test to evaluate changes in antibody levels across predetermined intervals with the Hochberg correction for multiple comparisons.

Results

Our results showed a significant initial rise in spike-directed IgG (S-IgG) and spike-directed IgA (S-IgA) levels, which remained elevated for the duration of the study. The S-IgG concentrations peaked 14 days afterboosting, while spike-directed IgM (S-IgM) levels were transient, aligning with their early response role. Notably, post-booster antibody concentrations did not significantly change. Prior S-IgG status influenced the post-priming S-IgA dynamics, with baseline S-IgG positive individuals maintaining higher S-IgA responses, a difference that did not reach statistical difference post-boost. Three instances of breakthrough infections: two among participants who exhibited baseline seropositivity for S-IgG, and one in a participant initially seronegative for S-IgG.

Discussion

In conclusion, the mRNA-1273 vaccine elicited robust and persistent S-IgG and S-IgA antibody responses, particularly after the first dose, indicating potential for long-term immunity. Prior viral exposure enhances post-vaccination S-IgA responses compared to naive individuals, which aligned with the prior-naïve, post-boost. The stable antibody levels observed post-booster dose, remaining high over an extended period, with no significant secondary rise, and no difference by baseline exposure, suggest that initial vaccination may sufficiently prime the immune system for prolonged protection in this population, allowing for potential to delay booster schedules as antibody responses remained high at the time of boosting. This finding calls for a reassessment of the booster dose scheduling in this demographic.

Challenges in Emerging Vaccines and Future Promising Candidates against SARS-CoV-2 Variants

Since the COVID-19 outbreak, the severe acute respiratory syndrome coronavirus 2 (SARS-COV-2) virus has evolved into variants with varied infectivity. Vaccines developed against COVID-19 infection have boosted immunity, but there is still uncertainty on how long the immunity from natural infection or vaccination will last. The present study attempts to outline the present level of information about the contagiousness and spread of SARS-CoV-2 variants of interest and variants of concern (VOCs). The keywords like COVID-19 vaccine types, VOCs, universal vaccines, bivalent, and other relevant terms were searched in NCBI, Science Direct, and WHO databases to review the published literature. The review provides an integrative discussion on the current state of knowledge on the type of vaccines developed against SARS-CoV-2, the safety and efficacy of COVID-19 vaccines concerning the VOCs, and prospects of novel universal, chimeric, and bivalent mRNA vaccines efficacy to fend off existing variants and other emerging coronaviruses. Genomic variation can be quite significant, as seen by the notable differences in impact, transmission rate, morbidity, and death during several human coronavirus outbreaks. Therefore, understanding the amount and characteristics of coronavirus genetic diversity in historical and contemporary strains can help researchers get an edge over upcoming variants.

Impaired humoral immunity following COVID-19 vaccination in HTLV-1 carriers

BACKGROUND

Whether human T-lymphotropic virus type 1 (HTLV-1) carriers can develop sufficient humoral immunity after coronavirus disease 2019 (COVID-19) vaccination is unknown.

METHODS

To investigate humoral immunity after COVID-19 vaccination in HTLV-1 carriers, a multicenter, prospective observational cohort study was conducted at five institutions in southwestern Japan, an endemic area for HTLV-1. HTLV-1 carriers and HTLV-1-negative controls were enrolled for this study from January to December 2022. During this period, the third dose of the COVID-19 vaccine was actively administered. HTLV-1 carriers were enrolled during outpatient visits, while HTLV-1-negative controls included health care workers and patients treated by participating institutions for diabetes, hypertension, or dyslipidemia. The main outcome was the effect of HTLV-1 infection on the plasma anti-COVID-19 spike IgG (IgG-S) titers after the third dose, assessed by multivariate linear regression with other clinical factors.

RESULTS

We analyzed 181 cases (90 HTLV-1 carriers, 91 HTLV-1-negative controls) after receiving the third dose. HTLV-1 carriers were older (median age 67.0 vs. 45.0 years, p < 0.001) and more frequently had diabetes, hypertension, or dyslipidemia than did HTLV-1-negative controls (60.0% vs. 27.5%, p < 0.001). After the third dose, the IgG-S titers decreased over time in both carriers and controls. Multivariate linear regression in the entire cohort showed that time since the third dose, age, and HTLV-1 infection negatively influenced IgG-S titers. After adjusting for confounders such as age, or presence of diabetes, hypertension, or dyslipidemia between carriers and controls using the overlap weighting propensity score method, and performing weighted regression analysis in the entire cohort, both time since the third dose and HTLV-1 infection negatively influenced IgG-S titers.

CONCLUSIONS

The humoral immunity after the third vaccination dose is impaired in HTLV-1 carriers; thus, customized vaccination schedules may be necessary for them.

Modeling of antibody responses to COVID-19 vaccination in patients with rheumatoid arthritis

To construct a model of the antibody response to COVID-19 vaccination in patients with rheumatoid arthritis (RA), and to identify clinical factors affecting the antibody response. A total of 779 serum samples were obtained from 550 COVID-19-naïve RA patients who were vaccinated against COVID-19. Antibody titers for the receptor binding domain (anti-RBD) and nucleocapsid (anti-N) were measured. The time from vaccination, and the log-transformed anti-RBD titer, were modeled using a fractional polynomial method. Clinical factors affecting antibody responses were analyzed by a regression model using generalized estimating equation. The anti-RBD titer peaked at about 2 weeks post-vaccination and decreased exponentially to 36.5% of the peak value after 2 months. Compared with the first vaccination, the 3rd or 4th vaccinations shifted the peaks of anti-RBD antibody response curves significantly upward (by 28-fold [4-195] and 32-fold [4-234], respectively). However, there was no significant shift in the peak from the 3rd vaccination to the 4th vaccination (p = 0.64). Multivariable analysis showed that sulfasalazine increased the vaccine response (by 1.49-fold [1.13-1.97]), but abatacept or JAK inhibitor decreased the vaccine response (by 0.13-fold [0.04-0.43] and 0.44-fold [0.26-0.74], respectively). Age was associated with lower ln [anti-RBD] values (coefficient: - 0.03 [- 0.04 to - 0.02]). In conclusion, the anti-RBD response of RA patients peaked at 2 weeks after COVID-19 vaccination, and then decreased exponentially, with the maximum peak increase observed after the 3rd vaccination. The antibody response was affected by age and the medications used to treat RA.

A multifaceted approach for identification, validation, and immunogenicity of naturally processed and in silico-predicted highly conserved SARS-CoV-2 peptides

SARS-CoV-2 remains a major global public health concern. Antibody waning and immune escape variant emergence necessitate the development of next generation vaccines that induce cross-reactive durable immune responses. T cell responses to SARS-CoV-2 demonstrate higher conservation, antigenic breadth, and longevity than antibody responses. Therefore, we sought to identify pathogen-derived T cell epitopes for a potential peptide-based vaccine. We pursued an approach leveraging: 1) liquid chromatography and tandem mass spectrometry (LC-MS/MS)-based identification of peptides from ancestral SARS-CoV-2-infected cell lines, 2) epitope prediction algorithms, and 3) overlapping peptide libraries. From this strategy, we identified 380 unique SARS-CoV-2-derived peptide sequences, including 53 antigenic HLA class I and class II peptides from multiple structural and non-structural/accessory viral proteins. These peptide sequences were highly conserved across variants of concern/interest (VoC/VoIs), and are estimated to achieve coverage of >96% of the world population. Our findings validate this discovery pipeline for peptide identification and immunogenicity testing, and are a crucial step toward the development of a next-generation multi-epitope SARS-CoV-2 peptide vaccine, and a novel vaccine platform methodology.

Detection of SARS-CoV-2-Specific Cells Utilizing Whole Proteins and/or Peptides in Human PBMCs Using IFN-ƴ ELISPOT Assay

SARS-CoV-2 continues to threaten global public health, making COVID-19 immunity studies of utmost importance. Waning of antibody responses postinfection and/or vaccination and the emergence of immune escape variants have been ongoing challenges in mitigating SARS-CoV-2 morbidity and mortality. While a tremendous amount of work has been done to characterize humoral immune responses to SARS-CoV-2 virus and vaccines, cellular immunity, mediated by T cells, is critical for efficient viral control and protection and demonstrates high durability and cross-reactivity to coronavirus variants. Thus, ELISPOT, a standard assay for antigen-specific cellular immune response assessment, allows us to evaluate SARS-CoV-2-specific T-cell response by quantifying the frequency of SARS-CoV-2-specific cytokine-secreting cells in vitro. We have outlined a detailed procedure to study T-cell recall responses to SARS-CoV-2 in human peripheral blood mononuclear cells (PBMCs) following infection and/or vaccination using an optimized IFN-γ ELISPOT assay. Our methodologies can be adapted to assess other cytokines and are a useful tool for studying other viral pathogen and/or peptide-specific T-cell responses.

The relative effectiveness of three and four doses of COVID-19 vaccine in Victoria, Australia: A data linkage study

BACKGROUND

The Coronavirus Disease 2019 (COVID-19) pandemic led to extensive vaccination campaigns worldwide, including in Australia. Immunity waning and the emergence of new viral variants pose challenges to the effectiveness of vaccines. Our study aimed to assess the relative effectiveness (rVE) of 3 and 4 compared with 2 doses of COVID-19 vaccine. The study focuses on the Victorian population, a majority of whom had no prior exposure to the virus before vaccination.

METHODS

We used routinely collected data for the state of Victoria, Australia, to assess rVE during an Omicron-dominant period, 1 June 2022 to 1 March 2023. Immunisation, notifications, hospitalisations and mortality data for residents aged 65 years and older were linked for analysis. Cox proportional hazard regression was used to estimate the rVE against COVID-19 hospitalisation or death, accounting for key confounders with vaccination as a time-varying covariate.

RESULTS

In 1,070,113 people 65 years or older who had received their second dose, a third and fourth dose of a COVID-19 vaccine significantly reduced the hazard of hospitalisation or death compared to two doses. rVE was highest within two weeks from administration at 40 % (95 % CI: 0 % to 64 %) and 66 % (95 % CI: 60 % to 71 %) for a third and fourth dose, respectively. Additional protection conferred by third and fourth doses waned over time from administration.

CONCLUSIONS

Our findings underscore the need for additional vaccine doses and updated vaccine strategies. These findings have implications for public health advice and COVID-19 vaccine strategies. Further research and monitoring of vaccine effectiveness in real-world settings are warranted to inform ongoing pandemic response efforts.

Diverging humoral and cellular immune responses due to Omicron-a national study from the Faroe Islands

IMPORTANCE

The immunity following infection and vaccination with the SARS-CoV-2 Omicron variant is poorly understood. We investigated immunity assessed with antibody and T-cell responses under different scenarios in vaccinated and unvaccinated individuals with and without Omicron infection. We found that the humoral response was higher among vaccinated-naïve than unvaccinated convalescent. Unvaccinated with and without infection had comparable low humoral responses, whereas vaccinated with a second or third dose, independent of infection status, had increasingly higher levels. Only a minor fraction of unvaccinated individuals had detectable humoral responses following Omicron infection, while almost all had positive T-cell responses. In conclusion, primary Omicron infection mounts a low humoral immune response, enhanced by prior vaccination. Omicron infection induced a robust T-cell response in both unvaccinated and vaccinated, demonstrating that immune evasion of primary Omicron infection affects humoral immunity more than T-cell immunity.

Riding high: seroprevalence of SARS-CoV-2 after 4 pandemic waves in Manitoba, Canada, April 2020-February 2022

BACKGROUND

Canada is emerging from the largest SARS-CoV-2 Omicron wave to date, with over 3.3 million confirmed cases. Unfortunately, PCR confirmed cases illuminate only a small portion of infections in the community and underestimate true disease burden. Population based seroprevalence studies, which measure antibody levels against a virus can more accurately estimate infection rates in the community and identify geographical and epidemiological trends to inform public health responses.

METHODS

The Manitoba COVID-19 Seroprevalence (MCS) study is a population-based cross-sectional study to assess the prevalence of SARS-CoV-2 antibodies across the province. Residual convenience specimens (n = 14,901) were tested for anti-SARS-CoV-2 nucleocapsid and spike IgG antibodies from April 1, 2020 to February 31, 2022. We estimated the monthly and cumulative prevalence using an exponential decay model, accounting for population demographics, sensitivity/specificity, and antibody waning. This approach generated estimates of natural infection as well as total antibody including vaccine-induced immunity within the community.

FINDINGS

After four waves of the pandemic, 60.1% (95%CI-56.6-63.7) of Manitobans have generated SARS-CoV-2 antibodies due to natural exposure independent of vaccination. Geographical analysis indicates a large portion of provincial prevalence stems from increased transmission in the Northern (92.3%) and Southern (71.8%) regional health authorities. Despite the high mortality rates reported by Manitoba, infection fatality ratios (IFR) peaked at 0.67% and declined to 0.20% following the Omicron wave, indicating parity with other national and international jurisdictions. Manitoba has achieved 93.4% (95%CI- 91.5-95.1) total antibody when including vaccination.

INTERPRETATION

Our data shows that more than 3 in 5 Manitobans have been infected by SARS-CoV-2 after four waves of the pandemic. This study also identifies key geographical and age specific prevalence rates that have contributed greatly to the overall severity of the pandemic in Manitoba and will inform jurisdictions considering reduction of public health measures.

Virologic Outcomes with Molnupiravir in Non-hospitalized Adult Patients with COVID-19 from the Randomized, Placebo-Controlled MOVe-OUT Trial

INTRODUCTION

The randomized, placebo-controlled, double-blind MOVe-OUT trial demonstrated molnupiravir (800 mg every 12 h for 5 days) as safe and effective for outpatient treatment of mild-to-moderate COVID-19, significantly reducing the risk of hospitalization/death in high-risk adults. At the time of that report, virologic assessments from the trial were partially incomplete as a result of their time-intensive nature. Here we present final results from all prespecified virology endpoints in MOVe-OUT based on the full trial dataset.

METHODS

Nasopharyngeal swabs were collected at baseline (day 1, prior to first dose) and days 3, 5 (end-of-treatment visit), 10, 15, and 29. From these samples, change from baseline in SARS-CoV-2 RNA titers (determined by quantitative PCR), detection of infectious SARS-CoV-2 (by plaque assay), and SARS-CoV-2 viral error induction (determined by whole genome next-generation sequencing) were assessed as exploratory endpoints.

RESULTS

Molnupiravir was associated with greater mean reductions from baseline in SARS-CoV-2 RNA than placebo (including 50% relative reduction at end-of-treatment) through day 10. Among participants with infectious virus detected at baseline (n = 96 molnupiravir, n = 97 placebo) and evaluable post-baseline samples, no molnupiravir-treated participant had infectious SARS-CoV-2 by day 3, whereas infectious virus was recovered from 21% of placebo-arm participants on day 3 and 2% at end-of-treatment. Consistent with molnupiravir's mechanism of action, sequence analysis demonstrated that molnupiravir was associated with an increased number of low-frequency transition errors randomly distributed across the SARS-CoV-2 RNA genome compared with placebo (median 143.5 molnupiravir, 15 placebo), while transversion errors were infrequent overall (median 2 in both arms). Outcomes were consistent regardless of baseline SARS-CoV-2 clade, presence of SARS-CoV-2-specific immune response, or viral load.

CONCLUSIONS

A 5-day course of orally administered molnupiravir demonstrated a consistently greater virologic effect than placebo, including rapidly eliminating infectious SARS-CoV-2, in high-risk outpatients with mild-to-moderate COVID-19.

TRIAL REGISTRATION

ClinicalTrials.gov, NCT04575597.

A prospective longitudinal cohort study on risk factors for COVID-19 vaccination failure (RisCoin): methods, procedures and characterization of the cohort

The primary objective of the RisCoin study was to investigate the interplay of genetic, metabolic, and lifestyle factors as well as stress levels on influencing the humoral immune response after at least two COVID-19 vaccinations, primarily with mRNAs, and the risk of SARS-CoV-2 breakthrough infections during follow-up. Here, we describe the study design, procedures, and study population. RisCoin is a prospective, monocentric, longitudinal, observational cohort study. Between October and December 2021, 4515 participants with at least two COVID-19 vaccinations, primarily BNT162b2 and mRNA-1273, were enrolled at the LMU University Hospital of Munich, thereof > 4000 healthcare workers (HCW), 180 patients with inflammatory bowel disease under immunosuppression, and 119 patients with mental disorders. At enrollment, blood and saliva samples were collected to measure anti-SARS-CoV-2 antibodies, their neutralizing capacity against Omicron-BA.1, stress markers, metabolomics, and genetics. To ensure the confidential handling of sensitive data of study participants, we developed a data protection concept and a mobile application for two-way communication. The application allowed continuous data reporting, including breakthrough infections by the participants, despite irreversible anonymization. Up to 1500 participants attended follow-up visits every two to six months after enrollment. The study gathered comprehensive data and bio-samples of a large representative HCW cohort and two patient groups allowing analyses of complex interactions. Our data protection concept combined with the mobile application proves the feasibility of longitudinal assessment of anonymized participants. Our concept may serve as a blueprint for other studies handling sensitive data on HCW.

Metabolic and toxicological considerations regarding CGRP mAbs and CGRP antagonists to treat migraine in COVID-19 patients: a narrative review

INTRODUCTION

Migraine pharmacological therapies targeting calcitonin gene-related peptide (CGRP), including monoclonal antibodies and gepants, have shown clinical effect and optimal tolerability. Interactions between treatments of COVID-19 and CGRP-related drugs have not been reviewed.

AREAS COVERED

An overview of CGRP, a description of the characteristics of each CGRP-related drug and its response predictors, COVID-19 and its treatment, the interactions between CGRP-related drugs and COVID-19 treatment, COVID-19 and vaccination-induced headache, and the neurological consequences of Covid-19.

EXPERT OPINION

Clinicians should be careful about using gepants for COVID-19 patients, due to the potential drug interactions with drugs metabolized via CYP3A4 cytochrome. In particular, COVID-19 treatment (especially nirmatrelvir packaged with ritonavir, as Paxlovid) should be considered cautiously. It is advisable to stop or adjust the dose (10 mg atogepant when used for episodic migraine) of gepants when using Paxlovid (except for zavegepant). CGRP moncolconal antibodies (CGRP-mAbs) do not have drug - drug interactions, but a few days' interval between a COVID-19 vaccination and the use of CGRP mAbs is recommended to allow the accurate identification of the possible adverse effects, such as injection site reaction. Covid-19- and vaccination-related headache are known to occur. Whether CGRP-related drugs would be of benefit in these circumstances is not yet known.

An agent-based model with antibody dynamics information in COVID-19 epidemic simulation

Accurate prediction of the temporal and spatial characteristics of COVID-19 infection is of paramount importance for effective epidemic prevention and control. In order to accomplish this objective, we incorporated individual antibody dynamics into an agent-based model and devised a methodology that encompasses the dynamic behaviors of each individual, thereby explicitly capturing the count and spatial distribution of infected individuals with varying symptoms at distinct time points. Our model also permits the evaluation of diverse prevention and control measures. Based on our findings, the widespread employment of nucleic acid testing and the implementation of quarantine measures for positive cases and their close contacts in China have yielded remarkable outcomes in curtailing a less transmissible yet more virulent strain; however, they may prove inadequate against highly transmissible and less virulent variants. Additionally, our model excels in its ability to trace back to the initial infected case (patient zero) through early epidemic patterns. Ultimately, our model extends the frontiers of traditional epidemiological simulation methodologies and offers an alternative approach to epidemic modeling.