Humoral and cellular immune correlates of protection against COVID-19 in kidney transplant recipients

Dynamics of SARS-CoV-2 IgG in Nursing Home Residents in Belgium Throughout Three BNT162b2 Vaccination Rounds: 19-Month Follow-Up

BACKGROUND/OBJECTIVES

This study mapped antibody dynamics across three COVID-19 vaccination rounds (primary course, first, and second booster with BNT162b2) in Belgian nursing home residents (NHRs).

METHODS

Within a national SARS-CoV-2 serosurveillance study (February 2021-September 2022) across Belgian nursing homes, dried blood spots were collected, on which anti-spike SARS-CoV-2 IgG antibodies were quantified by ELISA in international units/mL (IU/mL). Sociodemographic data were collected at the study start and infection history and vaccination data at each sampling round.

RESULTS

Infection-naïve NHRs had low antibody levels after primary course vaccination (geometric mean concentration (GMC) 292 IU/mL, 95% confidence interval (95% CI): 197-432), but increased tenfold after first booster (GMC 2168 IU/mL, 95% CI: 1554-3027). While antibodies among NHRs significantly declined within six months after primary vaccination (p < 0.0001), they remained stable for nine months post-booster (p > 0.05). Among primary vaccine non-responders, 92% (95% CI: 82-97%) developed antibodies after the first booster (GMC 594 IU/mL, 95% CI: 416-849), though tenfold lower than initial responders (GMC 4642 IU/mL, 95% CI: 3577-6022).

CONCLUSIONS

These findings demonstrate that NHRs require tailored vaccination, prioritizing repeated immunization to improve serological outcomes in poor responders such as infection-naive NHRs. Regular immune monitoring could aid in implementing evidence-based vaccine strategies, ensuring optimal protection for vulnerable populations against SARS-CoV-2 and other infectious threats.

Attenuated neutralization, maintained specificity: Humoral response to SARS-CoV-2 booster in kidney allograft recipients

Despite the lower virulence of current SARS-CoV-2 variants and high rates of vaccinated and previously infected subjects, COVID-19 remains a persistent threat in kidney transplant recipients (KTRs). This study evaluated the parameters of anti-SARS-CoV-2 antibody production in 120 KTRs. The production of neutralizing antibodies in KTRs, following booster vaccination with the mRNA vaccine BNT162b2, was significantly decreased and their decline was faster than in healthy subjects. Factors predisposing to the downregulation of anti-SARS-CoV-2 neutralizing antibodies included age, lower estimated glomerular filtration rate, and a full dose of mycophenolate mofetil. Neutralizing antibodies correlated with those targeting the SARS-CoV-2 receptor binding domain (RBD), SARS-CoV-2 Spike trimmer, total SARS-CoV-2 S1 protein, as well as with antibodies to the deadly SARS-CoV-1 virus. No cross-reactivity was found with antibodies against seasonal coronaviruses. KTRs exhibited lower postvaccination production of neutralizing antibodies against SARS-CoV-2; however, the specificity of their humoral response did not differ compared to healthy subjects.

COVID-19 clinical phenotypes in vaccinated and nonvaccinated solid organ transplant recipients: a multicenter validation study

Clinical phenotypes of COVID-19, associated with mortality risk, have been identified in the general population. The present study assesses their applicability in solid organ transplant recipients (SOTR) hospital-admitted by COVID-19. In a cohort of 488 SOTR, nonvaccinated (n = 394) and vaccinated (n = 94) against SARS-CoV-2, we evaluated 16 demographic, clinical, analytical, and radiological variables to identify the clinical phenotypes A, B, and C. The median age was 61.0 (51-69) years, 330 (67.6%) and 158 (32.4%) were men and women, respectively, 415 (85%) had pneumonia, and 161 (33%) had SpO2 < 95% at admission. All-cause mortality occurred in 105 (21.5%) cases. It was higher in nonvaccinated versus vaccinated SOTR (23.4% vs 13.8%, P = 0.04). Patients in the entire cohort were classified into phenotypes A (n = 149, 30.5%), B (n = 187, 38.3%), and C (n = 152, 31.1%), with mortality rates of 8.7%, 16.6%, and 40.1%, respectively, which were similar to those of nonvaccinated SOTR (9.5%, 16.7%, and 52.0%) and lower in vaccinated SOTR (4.4%, 15.8%, and 17.3%, respectively), with difference between nonvaccinated and vaccinated in the phenotype C (P < 0.001). In conclusion, COVID-19 clinical phenotypes are useful in SOTR, and all-cause mortality decreases in vaccinated patients.

Hybrid immunity protection against SARS-CoV-2 and severe COVID-19 in kidney transplantation: A retrospective, comparative cohort study

Hybrid immunity, resulting from a combination of SARS-CoV-2 infection and vaccination, offers robust protection against COVID-19 in the general population. However, its impact on immunocompromised patients remains unexplored. We investigated the effect of hybrid immunity against the Omicron variant in a population of kidney transplant recipients receiving the fourth dose mRNA monovalent vaccination. By extracting data from the clinical records and performing individual interviews, participants were categorized into the hybrid cohort (previously infected and vaccinated individuals) and the vaccine cohort (vaccinated-only individuals). The study comprised 1114 participants, 442 in the hybrid and 672 in the vaccine cohorts. From April 2022 to August 2023, 286 infections, 38 hospitalizations and 9 deaths were reported. The cumulative incidence of infection was 12.1% (95% confidence interval [CI], 9.03-16.03) for the hybrid cohort and 36.54% (95% CI, 32.81-40.54) for the vaccine cohort after 300 days of follow-up. Hybrid immunity was associated to a 72% lower risk of infection (adjusted hazard ratio, 0.28; 95% CI, 0.21-0.38) and a 96% lower risk of hospitalization (adjusted hazard ratio, 0.04; 95% CI, 0.01-0.32). No deaths occurred in the hybrid cohort. Hybrid immunity was associated with a lower incidence of SARS-CoV-2 infection and severe COVID-19, underscoring its importance for risk stratification in this vulnerable patient population.

Should SARS-CoV-2 serological testing be used in the decision to deliver a COVID-19 vaccine booster? A pro-con assessment

Anti-SARS-CoV-2 vaccination has saved millions of lives in the past few years. To maintain a high level of protection, particularly in at-risk populations, booster doses are recommended to counter the waning of circulating antibody levels over time and the continuous emergence of immune escape variants of concern (VOCs). As anti-spike serology is now widely available, it may be considered a useful tool to identify individuals needing an additional vaccine dose, i.e., to screen certain populations to identify those whose plasma antibody levels are too low to provide protection. However, no recommendations are currently available on this topic. We reviewed the relevant supporting and opposing arguments, including areas of uncertainty, and concluded that in most populations, spike serology should not be used to decide about the administration of a booster dose. The main counterarguments are as follows: correlates of protection are imperfectly characterised, essentially owing to the emergence of VOCs; spike serology has an intrinsic inability to comprehensively reflect the whole immune memory; and booster vaccines are now VOC-adapted, while the commonly available commercial serological assays explore antibodies against the original virus.

Persistent defect in SARS-CoV-2 humoral and cellular immunity in lung transplant recipients

Lung transplant recipients (LTRs) are susceptible to severe Coronavirus Disease 2019 (COVID-19) and had lower immune responses to primary severe acute respiratory syndrome-related to coronavirus 2 (SARS-CoV-2) vaccination as compared to the general population and to other solid organ transplant recipients. As immunity induced by booster vaccination and natural infection has increased since the beginning of the pandemic in the general population, immunity acquired by LTRs is not well documented. Humoral and cellular immunity to SARS-CoV-2 was monitored in February and May 2023 in 30 LTRs and compared to that of health care workers (HCWs) and nursing home residents (NHRs). LTRs had significantly lower levels of SARS-CoV-2 binding and neutralizing antibodies and lower interferon-gamma responses to Wuhan, Delta, and XBB1.5 variants as compared to HCWs and NHRs. Humoral immunity decreased between the 2 visits, whereas cellular immunity remained more stable. The persistent defect in SARS-CoV-2 immunity in LTRs should encourage continued monitoring and preventive measures for this vulnerable population.

Memory B Cells Provide Long-Term Protection to Vaccinated Kidney Transplant Recipients Against SARS-CoV-2 Variants

Kidney transplant recipients (KTRs) are highly vulnerable to COVID-19. An intensified scheme of vaccination offers short-term protection to the 50%-75% of KTRs able to develop a germinal center reaction, required for the generation of neutralizing titers of antibodies (NAbs). However, the duration of this vaccinal protection is unknown. In-depth longitudinal analysis of the immune response to vaccination of 33 KTRs demonstrates that the low peak of IgGs, the progressive decline in antibody titers, and the emergence of a variant of concerns (VOC) of SARS-CoV2, synergize to let 2/3 of responders to vaccine without NAbs after only a few months. Yet, a retrospective study of an independent cohort of 274 KTRs, revealed that the risk of severe COVID-19 in the latter was low, similar to that of patients with serum neutralizing capacity against VOC. Our work links this late vaccine protection with the presence of memory B cells, which are generated during the initial vaccine-induced germinal center reaction, have a wide repertoire directed against conserved spike epitopes, and rapidly differentiate into IgG-producing plasma cells upon antigenic rechallenge. We conclude that in contrast with a serological layer that goes fading rapidly, the cellular layer of humoral memory provides an efficient long-term protection against VOC to KTRs. This illustration of the complementary roles of the two layers of the humoral memory has implications in immunopathology beyond the COVID-19 in KTRs.

The future of integrated structural biology

Instruct-ERIC, "the European Research Infrastructure Consortium for Structural biology research," is a pan-European distributed research infrastructure making high-end technologies and methods in structural biology available to users. Here, we describe the current state-of-the-art of integrated structural biology and discuss potential future scientific developments as an impulse for the scientific community, many of which are located in Europe and are associated with Instruct. We reflect on where to focus scientific and technological initiatives within the distributed Instruct research infrastructure. This review does not intend to make recommendations on funding requirements or initiatives directly, neither at the national nor the European level. However, it addresses future challenges and opportunities for the field, and foresees the need for a stronger coordination within the European and international research field of integrated structural biology to be able to respond timely to thematic topics that are often prioritized by calls for funding addressing societal needs.

Rapid Wane and Recovery of XBB Sublineage Neutralization After Sequential Omicron-based Vaccination in Solid Organ Transplant Recipients

Durability of variant neutralization in solid organ transplant recipients following Omicron-containing boosters is unknown. We report wane in XBB.1.5 neutralization by 3 months following a first bivalent booster, improved by a second booster; hybrid immunity improved peak, and duration of neutralization. Boosting at 3 to 6 months appears necessary to maintain neutralization.

Follow-Up of SARS-CoV-2 Antibody Levels in Belgian Nursing Home Residents and Staff Two, Four and Six Months after Primary Course BNT162b2 Vaccination

When COVID-19 vaccines were implemented, nursing home residents (NHRs) and staff (NHS) in Belgium were prioritized for vaccination. To characterize the vaccine response over time in this population and to identify poorly responding groups, we assessed antibody concentrations two (T1), four (T2) and six months (T3) after primary course BNT162b2 vaccination in six groups of infection-naive/infection-primed NHRs/NHS, with/without comorbidity (NHRs only). Participant groups (N = 125 per group) were defined within a national serosurveillance study in nursing homes, based on questionnaire data. Dried blood spots were analyzed using ELISA for the quantification of SARS-CoV-2 S1RBD IgG antibodies. Among all groups, antibody concentrations significantly decreased between T1 and T2/T3, all with a ≥70% decrease at T3, except for infection-primed staff (-32%). Antibody concentrations among infection-naive NHRs were 11.96 times lower than those among infection-primed NHR, while the latter were comparable (x1.05) to infection-primed NHS. The largest proportion [13% (95% CI: 11-24%)] of vaccine non-responders was observed in the group of infection-naive NHRs with comorbidities. A longer interval between infection and vaccination (≥3 months) elicited higher antibody responses. Our data retrospectively show the necessity of timely COVID-19 booster vaccination. Infection-naive NHRs require special attention regarding immune monitoring in future epidemics or pandemics.

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.

SARS-CoV-2-specific cellular and humoral immunity after bivalent BA.4/5 COVID-19-vaccination in previously infected and non-infected individuals

Knowledge is limited as to how prior SARS-CoV-2 infection influences cellular and humoral immunity after booster-vaccination with bivalent BA.4/5-adapted mRNA-vaccines, and whether vaccine-induced immunity may indicate subsequent infection. In this observational study, individuals with prior infection (n = 64) showed higher vaccine-induced anti-spike IgG-antibodies and neutralizing titers, but the relative increase was significantly higher in non-infected individuals (n = 63). In general, both groups showed higher neutralizing activity towards the parental strain than towards Omicron-subvariants BA.1, BA.2 and BA.5. In contrast, CD4 or CD8 T cell levels towards spike from the parental strain and the Omicron-subvariants, and cytokine expression profiles were similar irrespective of prior infection. Breakthrough infections occurred more frequently among previously non-infected individuals, who had significantly lower vaccine-induced spike-specific neutralizing activity and CD4 T cell levels. In summary, we show that immunogenicity after BA.4/5-bivalent vaccination differs between individuals with and without prior infection. Moreover, our results may help to improve prediction of breakthrough infections.

Immune and behavioral correlates of protection against symptomatic post-vaccination SARS-CoV-2 infection

Introduction

We sought to determine pre-infection correlates of protection against SARS-CoV-2 post-vaccine inzfections (PVI) acquired during the first Omicron wave in the United States.

Methods

Serum and saliva samples from 176 vaccinated adults were collected from October to December of 2021, immediately before the Omicron wave, and assessed for SARS-CoV-2 Spike-specific IgG and IgA binding antibodies (bAb). Sera were also assessed for bAb using commercial assays, and for neutralization activity against several SARS-CoV-2 variants. PVI duration and severity, as well as risk and precautionary behaviors, were assessed by questionnaires.

Results

Serum anti-Spike IgG levels assessed by research assay, neutralization titers against Omicron subvariants, and low home risk scores correlated with protection against PVIs after multivariable regression analysis. Commercial assays did not perform as well as research assay, likely due to their lower dynamic range.

Discussion

In the 32 participants that developed PVI, anti-Spike IgG bAbs correlated with lower disease severity and shorter duration of illness.

Direct and indirect impact of the COVID-19 pandemic on the survival of kidney transplant recipients: A national observational study in France

During the pandemic period, health care systems were substantially reorganized for managing COVID-19 cases. Corresponding consequences on persons with chronic diseases remain insufficiently documented. This observational cohort study investigated the direct and indirect impact of the pandemic period on the survival of kidney transplant recipients (KTR). Using the French National Health Data System, incident persons with end-stage kidney disease between 2015 and 2020, and who received a kidney transplant during this period were included and followed up from their transplantation date to December 31, 2021. The survival of KTR during the prepandemic and pandemic periods was investigated using Cox models with time-dependent covariates. There were 10 637 KTR included in the study, with 324 and 430 deaths observed during the prepandemic and pandemic periods, respectively. The adjusted risk of death during the pandemic period was similar to that observed during the prepandemic period (hazard ratio [HR] [95% confidence interval]: 0.92 [0.77-1.11]), COVID-19-related hospitalization was associated with an increased risk of death (HR: 10.62 [8.46-13.33]), and a third vaccine dose was associated with a lower risk of death (HR: 0.42 [0.30-0.57]). The pandemic period was not associated with an indirect higher risk of death in KTR with no COVID-19-related hospitalization.

Association Between Low Anti-spike Antibody Levels After the Third Dose of SARS-CoV-2 Vaccination and Hospitalization due to Symptomatic Breakthrough Infection in Kidney Transplant Recipients

Background

Whether anti-severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) antibody levels post-third coronavirus disease (COVID-19) vaccination correlate with worse outcomes due to breakthrough infection is unclear. We evaluated the association between anti-SARS-CoV-2 antibody levels and symptomatic breakthrough infection or hospitalization during the Omicron surge in kidney transplant recipients.

Methods

In total, 287 kidney transplant recipients expected to receive a third vaccination were enrolled between November 2021 and February 2022. The Abbott SARS-CoV-2 IgG II Quant test (Abbott, Chicago, IL, USA) was performed within three weeks before and four weeks after the third vaccination. The incidence of symptomatic breakthrough infection and hospitalization from two weeks to four months post-third vaccination was recorded.

Results

After the third vaccination, the seropositive rate and median antibody titer of the 287 patients increased from 57.1% to 82.2% and from 71.7 (interquartile range [IQR] 7.2-402.8) to 1,612.1 (IQR 153.9-5,489.1) AU/mL, respectively. Sixty-four (22.3%) patients had symptomatic breakthrough infections, of whom 12 required hospitalization. Lower anti-receptor-binding domain (RBD) IgG levels (<400 AU/mL) post-third vaccination were a risk factor for symptomatic breakthrough infection (hazard ratio [HR]=3.46, P<0.001). Anti-RBD IgG levels <200 AU/mL were a critical risk factor for hospitalization (HR=36.4, P=0.007).

Conclusions

Low anti-spike IgG levels after third vaccination in kidney transplant recipients were associated with symptomatic breakthrough infection and, particularly, with hospitalization during the Omicron surge. These data can be used to identify patients requiring additional protective measures, such as passive immunization using monoclonal antibodies.

Humoral and cellular immunity against different SARS-CoV-2 variants in patients with chronic kidney disease

Chronic kidney disease (CKD) patients are at higher risk of severe COVID-19. Humoral and cellular immunity from prior infection or vaccination are important for protection, but the neutralizing antibody (nAb) response against SARS-CoV-2 variants is impaired. We investigated the variant-specific nAb and T cell immunity among CKD patients. Adult CKD patients were recruited between August and October 2022. nAb against the SARS-CoV-2 (ancestral strains and four Omicron sublineages) and T cell response were measured using the live virus neutralization assay and interferon-gamma release assay (IGRA). The correlation between nAb/T-cell response and subsequent infection after recruitment were also determined. Among the 88 recruited patients, 95.5% had prior infection or had completed the primary vaccine series. However, only 77.3% had detectable nAb against at least one SARS-CoV-2 strains, 59.1% tested positive in IGRA, and 52.3% had detectable nAb and tested positive in the IGRA. The nAb geometic mean titers (GMTs) against XBB.1, BA.5 and BA.2.3.20 were significantly lower than those against BA.2 and ancestral strain. Prior SARS-CoV-2 infection was associated with elevated nAb and T cell response. More kidney transplant recipients (KTRs) showed absent nAb and T cell response (36.8% vs. 10.1%), despite a higher prevalence of vaccine booster in this population (94.7% vs. 50.7%). Lower levels of nAb titer and T cell response were significantly associated with subsequent infection. A considerable proportion of CKD patients, especially KTRs, showed absence of humoral and cellular protective immunity against SARS-CoV-2. Strategies to improve immunogenicity in this population are urgently needed.

Cellular immune response of SARS-CoV-2 vaccination in kidney transplant recipients: a systematic review and meta-analysis

Background

Evidence has demonstrated inferior humoral immune responses after SARS-CoV-2 vaccination in kidney transplant recipients compared to the general population. However, data on cellular immune responses in this population have not been established.

Methods

We searched the MEDLINE, Scopus, and Cochrane databases and included studies reporting cellular immune response rates in kidney transplant recipients after receiving SARS-CoV-2 vaccines. Studies that reported factors associated with cellular immune responders or non-responders were also included (PROSPERO: CRD42022375544).

Results

From a total of 1,494 articles searched, 53 articles were included in the meta-analysis. In all, 21 studies assessed cellular immune response by interferon-γ enzyme-linked immunosorbent spot (IFN-γ ELISPOT), 22 studies used interferon-γ release assay (IGRA), and 10 studies used flow cytometric analysis. The pooled response rate after two doses (standard regimen) and three doses of vaccination was 47.5% (95%CI 38.4-56.7%) and 69.1% (95%CI 56.3-80.6%) from IFN-γ ELISPOT, 25.8% (95%CI 19.7-32.4%) and 14.7% (95%CI 8.5-22.2%) from IGRA, and 73.7% (95%CI 55.2-88.8%) and 86.5% (95%CI 75.3-94.9%) from flow cytometry, respectively. Recipients with seroconversion were associated with a higher chance of having cellular immune response (OR 2.58; 95%CI 1.89-3.54). Cellular immune response in kidney transplant recipients was lower than in dialysis patients (OR 0.24; 95%CI 0.16-0.34) and the general population (OR 0.10; 95%CI 0.07-0.14). Age and immunosuppressants containing tacrolimus or corticosteroid were associated with inferior cellular immune response.

Conclusion

Cellular immune response after SARS-CoV-2 vaccination in kidney transplant recipients was lower than in dialysis patients and the general population. Age, tacrolimus, and corticosteroid were associated with poor response. Cellular immune response should also be prioritized in vaccination studies.

Systematic review registration

https://www.crd.york.ac.uk/prospero/, identifier CRD42022375544.

Robust spike-specific CD4+ and CD8+ T cell responses in SARS-CoV-2 vaccinated hematopoietic cell transplantation recipients: a prospective, cohort study

Poor overall survival of hematopoietic stem cell transplantation (HSCT) recipients who developed COVID-19 underlies the importance of SARS-CoV-2 vaccination. Previous studies of vaccine efficacy have reported weak humoral responses but conflicting results on T cell immunity. Here, we have examined the relationship between humoral and T cell response in 48 HSCT recipients who received two doses of Moderna's mRNA-1273 or Pfizer/BioNTech's BNT162b2 vaccines. Nearly all HSCT patients had robust T cell immunity regardless of protective humoral responses, with 18/48 (37%, IQR 8.679-5601 BAU/mL) displaying protective IgG anti-receptor binding domain (RBD) levels (>2000 BAU/mL). Flow cytometry analysis of activation induced markers (AIMs) revealed that 90% and 74% of HSCT patients showed reactivity towards immunodominant spike peptides in CD8⁺ and CD4⁺ T cells, respectively. The response rate increased to 90% for CD4⁺ T cells as well when we challenged the cells with a complete set of overlapping peptides spanning the entire spike protein. T cell response was detectable as early as 3 months after transplant, but only CD4⁺ T cell reactivity correlated with IgG anti-RBD level and time after transplantation. Boosting increased seroconversion rate, while only one patient developed COVID-19 requiring hospitalization. Our data suggest that HSCT recipients with poor serological responses were protected from severe COVID-19 by vaccine-induced T cell responses.

Booster Dose of SARS-CoV-2 mRNA Vaccine in Kidney Transplanted Patients Induces Wuhan-Hu-1 Specific Neutralizing Antibodies and T Cell Activation but Lower Response against Omicron Variant

Kidney transplanted recipients (KTR) are at high risk of severe SARS-CoV-2 infection due to immunosuppressive therapy. Although several studies reported antibody production in KTR after vaccination, data related to immunity to the Omicron (B.1.1.529) variant are sparse. Herein, we analyzed anti-SARS-CoV-2 immune response in seven KTR and eight healthy controls after the second and third dose of the mRNA vaccine (BNT162b2). A significant increase in neutralizing antibody (nAb) titers were detected against pseudoviruses expressing the Wuhan-Hu-1 spike (S) protein after the third dose in both groups, although nAbs in KTR were lower than controls. nAbs against pseudoviruses expressing the Omicron S protein were low in both groups, with no increase after the 3rd dose in KTR. Reactivity of CD4⁺ T cells after boosting was observed when cells were challenged with Wuhan-Hu-1 S peptides, while Omicron S peptides were less effective in both groups. IFN-γ production was detected in KTR in response to ancestral S peptides, confirming antigen-specific T cell activation. Our study demonstrates that the 3rd mRNA dose induces T cell response against Wuhan-Hu-1 spike peptides in KTR, and an increment in the humoral immunity. Instead, humoral and cellular immunity to Omicron variant immunogenic peptides were low in both KTR and healthy vaccinated subjects.

Predicting vaccine effectiveness against severe COVID-19 over time and against variants: a meta-analysis

Vaccine protection from symptomatic SARS-CoV-2 infection has been shown to be strongly correlated with neutralising antibody titres; however, this has not yet been demonstrated for severe COVID-19. To explore whether this relationship also holds for severe COVID-19, we performed a systematic search for studies reporting on protection against different SARS-CoV-2 clinical endpoints and extracted data from 15 studies. Since matched neutralising antibody titres were not available, we used the vaccine regimen, time since vaccination and variant of concern to predict corresponding neutralising antibody titres. We then compared the observed vaccine effectiveness reported in these studies to the protection predicted by a previously published model of the relationship between neutralising antibody titre and vaccine effectiveness against severe COVID-19. We find that predicted neutralising antibody titres are strongly correlated with observed vaccine effectiveness against symptomatic (Spearman [Formula: see text] = 0.95, p < 0.001) and severe (Spearman [Formula: see text] = 0.72, p < 0.001 for both) COVID-19 and that the loss of neutralising antibodies over time and to new variants are strongly predictive of observed vaccine protection against severe COVID-19.