BNT162b2 Third Booster Dose Significantly Increases the Humoral Response Assessed by Both RBD IgG and Neutralizing Antibodies in Renal Transplant Recipients

The immunologic outcomes and adverse events of COVID-19 vaccine booster dose in immunosuppressed people: A systematic review

Introduction

This study examines the efficacy and safety of three COVID-19 booster vaccines including mRNA-based vaccines (BNT162b2 (BioNTech/Pfizer) and/or mRNA-1273 (Moderna)), Non-Replicating Viral-Vector vaccines (ChAdOx1 nCoV-19 vaccine (AstraZeneca) and/or Ad26. COV2.S (Johnson & Johnson)), and Protein Subunit vaccine (SpikoGen) in immunosuppressed patients.

Methods

Relevant articles were systematically searched using medical subject heading (MeSH) and keywords "COVID-19" and "booster dose" or "booster vaccine" or ''fourth dose" in the online databases of PubMed, Embase, Scopus, and Web of Science. To identify eligible studies, a two-phase screening process was implemented. Initially, three researchers evaluated the studies based on the relevancy of the title and abstract.

Results

A total of 58 studies met the inclusion criteria and were included in this review. The findings suggest that booster doses offer greater protection against the disease than the primary dose. The study also compared various vaccine types, revealing that viral vector and nucleic acid vaccines outperformed inactivated vaccines. Results indicated that individuals receiving booster doses experienced superior outcomes compared to those without boosters. Vaccination against COVID-19 emerged as the most effective preventive measure against infection and symptom severity. Elevated antibody levels post-booster dose vaccination in the population signaled robust immune responses, underscoring the benefits of supplementary vaccine doses.

Conclusion

This systematic review highlights preliminary evidence supporting the immunologic outcomes and safety of COVID-19 vaccine boosters in enhancing immune responses against SARS-CoV-2. However, further research is needed to determine optimal timing intervals between primary vaccination series and boosters while considering global equity issues and variant-specific considerations.

Elevated hemoglobin levels in renal transplant recipients with polycystic kidney disease versus other etiologies: exploring mechanisms and implications for outcomes

BACKGROUND

Autosomal dominant polycystic kidney disease (ADPKD)-related end-stage kidney disease (ESKD) often necessitates transplantation. However, the impact of ADPKD on post-transplant outcomes, specifically hemoglobin levels, remains unknown.

METHODS

We retrospectively analyzed 513 Kidney Transplant Recipients (KTRs), of whom 81 had ESKD due to ADPKD (20 with pre-transplant native nephrectomy and 61 without). Hemoglobin levels were evaluated at multiple time intervals post-transplant.

RESULTS

Kidney transplant recipients with ADPKD vs. KTRs with ESKD due to other causes exhibited significantly higher hemoglobin levels in repeated measurement analysis. Multivariable analyses confirmed ADPKD as an independent predictor for elevated hemoglobin levels. In a multivariable logistic regression analysis, the odds for maximum hemoglobin > 15 mg/dL at 3-12 months post-transplant were more than twice as high in ADPKD patients vs. all the other KTRs (Odds Ratio [OR] 2.31, 95% Confidence Interval [CI] 1.3-4.13, p < 0.001). Pre-transplant native nephrectomy revealed a trend toward lower hemoglobin levels. Elevated hemoglobin levels were linked to improved estimated glomerular filtration rate (eGFR) at one year post-transplant. Patient survival was enhanced among KTRs with ADPKD compared to other ESKD causes.

CONCLUSIONS

Kidney transplant recipients with ADPKD exhibited elevated hemoglobin levels post-transplant, possibly due to prolonged native kidney erythropoietin production. These elevated hemoglobin levels were linked to improved outcomes, including allograft function and patient survival. Future research should further investigate the underlying mechanisms driving favorable ADPKD KTR outcomes.

Antibody responses after BNT162b2 vaccination in Japanese geriatric intermediate care facilities

Background

To evaluate antibody responses against the primary series of vaccination of severe acute respiratory syndrome coronavirus-2 [SARS-CoV-2] vaccines in the staff and residents of Japanese geriatric intermediate care facilities.

Methods

All subjects (159 staff and 96 residents) received two doses of the BNT162b2 mRNA vaccine 3 weeks apart. Baseline data of subject were collected using a structured form. Serum samples were collected three times: before vaccination, 3 weeks after the first dose, and 4 weeks after the second dose, and anti-receptor binding domain of the spike protein of SARS-CoV-2 [anti-RBD] IgG was measured using two immunoassays.

Results

After the second dose, geometric mean titers [GMT] of anti-RBD with both the Abbott and Roche assay were significantly lower in residents than staff (2282 AU/mL vs. 8505 AU/mL, and 258 U/mL vs. 948 U/mL, respectively). Multivariate analysis of characteristics affecting antibody responses (≥1280 AU/mL for Abbott and > 210 U/mL for Roche) showed lower odds ratios [ORs] for older age (adjusted OR per 10 year increase [aOR] = 0.62, 95 % confidence interval [95 %CI]; 0.38-1.02), steroid usage (aOR = 0.09, 95 %CI; 0.01-0.60) and regular nonsteroidal anti-inflammatory drugs [NSAIDs] usage (aOR = 0.16, 95 %CI; 0.03-0.88).

Conclusions

Elderly people and steroid and NSAID users had lower antibody responses following the second vaccine dose.

Humoral and Cellular Immunity Are Significantly Affected in Renal Transplant Recipients, following Vaccination with BNT162b2

BACKGROUND

Renal transplant recipients (RTRs) tend to mount weaker immune responses to vaccinations, including vaccines against the novel severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2).

METHODS

Humoral immunity was assessed using anti-receptor binding domain (RBD) and neutralizing antibodies (NAb) serum levels measured by ELISA, and cellular immunity was assessed using T-, B-, NK, natural killer-like T (NKT)-cell subpopulations, and monocytes measured by flow cytometry, and also specific T-cell immunity, at predefined time points after BNT162b2 vaccination, in 57 adult RTRs.

RESULTS

Administration of three booster doses was necessary to achieve anti-RBD and NAb protective levels in almost all patients (92.98%). Ab production, at several time points, was positively correlated with the corresponding renal function and inversely correlated with hemodialysis vintage (HDV) and treatment with mycophenolic acid (MPA). A gradual rise in several cell subpopulations, including total lymphocytes (p = 0.026), memory B cells (p = 0.028), activated CD4 (p = 0.005), and CD8 cells (p = 0.001), was observed even after the third vaccination dose, while a significant reduction in CD3+PD1+ (p = 0.002), NKT (p = 0.011), and activated NKT cells (p = 0.034) was noted during the same time interval. Moreover, SARS-CoV-2-specific T-cells were present in 41% of the patients who were unable to develop Nabs, and their positivity rates four months after the second dose were in inverse correlation with monocytes (p = 0.045) and NKT cells (p = 0.01).

CONCLUSIONS

SARS-CoV-2-specific T-cell responses preceded the humoral ones, while two booster doses were needed for this group of immunocompromised patients to mount a protective immune response.

Humoral response to SARS-CoV-2 mRNA vaccine on in ABO blood type incompatible kidney transplant recipients treated with low-dose rituximab

We aimed to evaluate the humoral response after the second and third doses of SARS-CoV-2 mRNA vaccine in ABO blood type incompatible kidney transplant (KT) recipients treated with rituximab. This retrospective study conducted between June 2021 and June 2022 included 131 KT recipients and 154 nontransplant controls who had received mRNA vaccines. We compared the seropositivity (anti-SARS-CoV-2 spike IgG antibody titer ≥ 0.8 U/mL) after the second and third vaccinations. Furthermore, we evaluated the impact of pretransplant vaccination for seropositivity. Of the 131 KT recipients, 50 had received the third dose of mRNA vaccine. The antibody titer was significantly increased after the third dose of mRNA vaccine. The seropositivity rate after the third dose of mRNA vaccine increased from 36 to 70%. We observed no significant difference in seropositivity after the third dose of mRNA vaccine in ABO incompatibility, rituximab use, mycophenolate mofetil use, and age at KT. Of the nine recipients who had received the second or third dose of the mRNA vaccine prior to the KT, eight of the recipients were seropositive both before and after the KT. Our results suggest that ABO incompatibility or rituximab use was not significantly associated with seropositivity.

Humoral vaccine response and breakthrough infections in kidney transplant recipients during the COVID-19 pandemic: a nationwide cohort study

Background

Kidney transplant recipients (KTRs) experienced reduced SARS-CoV-2 vaccine response and were at increased risk of severe COVID-19. It is unknown if level of vaccine induced anti-receptor binding domain IgG (anti-RBD IgG) correlates with protection from and survival following COVID-19. We aimed to evaluate the effect of vaccine response on risk of breakthrough infections (BTI) and COVID-19 death in KTRs.

Methods

We performed a nationwide study, examining the competing risk of SARS-CoV-2 infection, COVID-19 related/unrelated death, and vaccine efficacy as assessed by level of anti-RBD IgG response 4-10 weeks after each vaccination. The study included all KTR in Norway alive and with a functioning graft on February 20th, 2020, and events after November 11th, 2022 were right-censored. A pre-pandemic reference-cohort from January 1st 2019 to January 1st 2020 was included to evaluate excess mortality. The study was conducted at Oslo University Hospital, Rikshospitalet, Norway.

Findings

The study included 3607 KTRs (59 [48-70] years) with a functioning graft at February 20th, 2020, who received (median [IQR]) 4 [3-4] vaccines (range 2-6, 99% mRNA). Anti-RBD IgG was measured in 12 701 serum samples provided by 3213 KTRs. Vaccine response was assessed 41 [31-57] days after vaccination. A total of 1090 KTRs were infected with SARS-CoV-2, 1005 (92%) were BTI, and vaccine response did not protect against BTI. The hazard ratio for COVID-19 related death 40 days post-infection was 1.71 (95% CI: 1.14, 2.56) comparing vaccine response levels (≥5 vs. ≥5000 BAU/mL). No excess non-COVID-19 mortality was registered in KTRs surviving SARS-CoV-2 infection compared to a 2019 pre-pandemic reference.

Interpretation

Our findings suggested that SARS-CoV-2 mRNA vaccine response did not predict protection against infection, but prevention of fatal disease progression in KTRs and greater vaccine response further reduced the risk of COVID-19 death. No excess non-COVID-19 mortality was seen during the pandemic.

Funding

CEPI and internal funds.

The Clinical Manifestation of Immunosuppressive Therapy as a Tool to Improve Immune Monitoring in Renal Transplant Recipients

INTRODUCTION

Metrics for posttransplant immune monitoring to prevent over or under immunosuppression in renal transplant recipients (RTRs) are lacking.

METHODS

We surveyed 132 RTRs, 38 in the first year posttransplant and 94 >1-year posttransplant, to study the clinical expression of immunosuppressive therapy. A questionnaire administered to these RTRs was divided into physical (Q physical) and mental (Q mental) symptoms.

RESULTS

In multivariable models for the association between the calculated Q physical and Q mental scores and different clinical and biochemical variables in the 38 RTRs who filled out the questionnaire 130 times during the first year posttransplant, it was found that mycophenolic acid (MPA) and prednisone use increased the mean Q physical score by 0.59 (95% CI: 0.21-0.98, p = 0.002) and 0.53 (95% CI: 0.26-0.81, p = 0.00), respectively, while MPA use increased the mean Q mental score by 0.72 (95% CI: 0.31-1.12, p = 0.001). Among the 94 RTRs who each completed the questionnaire only once, the odds for the mean Q mental score to be above the median value were more than 3 times higher for RTRs treated versus non-treated with MPA (OR 3.38, 95% CI: 1.1-10.3, p = 0.03). MPA-treated RTRs had higher mean scores for questions related to sleep disorders (1.83 ± 1.06 vs. 1.32 ± 0.67 for not treated, p = 0.037), to difficulty falling asleep (1.72 ± 1.11 vs. 1.16 ± 0.5, p = 0.02), and to depression and anxiety.

CONCLUSION

We concluded that prednisone and MPA use are associated with an increased Q physical and Q mental scores in RTRs. Routine monitoring of physical and mental status of RTRs should be implemented to improve the diagnosis of overimmunosuppression. Dose reduction or discontinuation of MPA should be considered in RTRs who report sleep disorders, depression, and anxiety.

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.

Efficacy and safety of booster vaccination against SARS-CoV-2 in dialysis and renal transplant patients: systematic review and meta-analysis

INTRODUCTION

Patients under renal replacement therapy are at an increased risk of severe infection with SARS-CoV-2, and have been known to have impaired response to standard vaccination. This systematic review and meta-analysis aims at evaluating the efficacy of booster dose vaccination in this population.

METHODS

A systematic review has been conducted to find trials on the booster dose vaccination in kidney transplant recipients (KTRs) or patients under dialysis. Data of seroconversion rates at different timepoints, especially 1 month prior and post-booster dose vaccination have been collected and analyzed. Effects of different factors including type of renal replacement therapy (RRT), vaccine type and brands, magnitude of response to the standard vaccination, and immunosuppression drugs on the response rates have been investigated. Meta-analyses were performed using software Stata v.17.

RESULTS

Overall 58 studies were included. Both RRT patient subgroups represented significant seroconversion, post- (versus pre-) booster dose vaccination, but only in KTRs the booster dose seroconversion surpassed that of the standard protocol. T-cell response was also significantly augmented after booster vaccination, with no difference between the RRT subgroups. mRNA and vector vaccine types had comparable immunogenicity when employed as boosters, both significantly higher than the inactivated virus vaccine, with no significant disparity regarding the vaccine brands. Patients with poor response to standard vaccination had a significant response to booster dose, with dialysis patients having stronger response. The differential effects of vaccine types and brands in the poor responders was similar to that of the overall RRT population. No rejection episodes or graft failure post-booster vaccination was reported.

CONCLUSION

In patients under RRT, booster dose vaccination against SARS-CoV-2 is safe and efficacious determined by significant seroconversion, and therefore, it should be considered to be implemented in all these patients. Since in the KTR patients, the third dose vaccination significantly increased the seroconversion rates even beyond that of the standard protocol, three dose vaccine doses is recommended to be recognized as the standard vaccination protocol in this population. The same recommendation could be considered for dialysis patients, due to their augmented risk of breakthrough infection.

Humoral Response to the Fourth BNT162b2 Vaccination and Link Between the Fourth Dose, Omicron Infection, and Disease Severity in Renal Transplant Recipients

BACKGROUND

The effectiveness of the fourth BNT162b2 vaccination in reducing the rate and severity of coronavirus disease 2019 (COVID-19) caused by the Omicron variant in renal transplant recipients (RTRs) is unknown.

METHODS

Interviews were conducted with 447 RTRs regarding the status and timing of the fourth vaccination, prior vaccinations, and preceding COVID-19 infection. RTRs with polymerase chain reaction-confirmed COVID-19 infection from December 1, 2021, to the end of March 2022 were considered to have been infected with the Omicron variant and were interviewed to determine their disease severity. In a subgroup of 74 RTRs, the humoral response to the fourth dose was analyzed. In 30 RTRs, microneutralization assays were performed to reveal the humoral response to wild-type, Delta, and Omicron variant isolates before and after the fourth dose.

RESULTS

Of 447 RTRs, 144 (32.2%) were infected with the Omicron variant, with 71 (49.3%) of the infected RTRs having received the fourth vaccine dose. RTRs who did not receive the fourth dose before the infection had more serious illness. In a subgroup of 74 RTRs, the fourth dose elicited a positive humoral response in 94.6% (70/74), with a significant increase in geometric mean titer for receptor-binding domain immunoglobulin G and neutralizing antibodies ( P  < 0.001). The humoral responses to the Omicron variant before and after the fourth dose were significantly lower than the responses to the wild-type and the Delta variants.

CONCLUSIONS

Overall, the fourth BNT162b2 dose was effective in reducing the rate and severity of Omicron disease in RTRs, despite the reduced humoral response to the variant.

SARS-CoV-2 antibody responses post-vaccination in UK healthcare workers with pre-existing medical conditions: a cohort study

OBJECTIVES

To examine antibody responses after the second vaccination in healthcare workers (HCWs) with underlying health conditions.

DESIGN

Cohort study.

SETTING

Oxford University Hospitals in the United Kingdom.

PARTICIPANTS

Healthcare workers who had SARS-CoV-2 serological data available and received two SARS-CoV- 2 vaccinations.

PRIMARY OUTCOME

Peak SARS-CoV-2 anti-spike IgG responses after the second vaccination and associations with underlying health conditions and the estimated risk of severe COVID-19 using an occupational health risk assessment tool.

METHODS

We used univariable and multivariable linear regression models to investigate associations between antibody levels and demographics (age, sex, ethnicity), healthcare role, body mass index, underlying health conditions, vaccination status, prior infection and the Association of Local Authority Medical Advisors COVID-age risk score.

RESULTS

1635 HCWs had anti-spike IgG measurements 14-84 days after second vaccination and data on any underlying health conditions. Only five HCWs (0.3%), all on immunosuppressive treatment, (including four organ transplant recipients), did not seroconvert after second vaccination. Antibody levels were independently lower with older age, diabetes, immunosuppression, respiratory disorders other than asthma and markedly so in organ transplant recipients. Levels were independently lower in ChAdOx1 versus BNT162b2 recipients and higher following previous infection. HCWs with 'very high' COVID-age risk scores had lower median antibody levels than those with 'low', 'medium' or 'high' risk scores; 4379 AU/mL, compared with 12 337 AU/mL, 9430 AU/mL and 10 524 AU/mL, respectively.

CONCLUSIONS

Two vaccine doses are effective in generating antibody responses among HCWs, including those with a high occupational risk. However, HCWs with underlying health conditions, especially diabetes, immunosuppression and organ transplant, had lower antibody levels, and vaccine response monitoring may be needed.

A systematic review assessing the effectiveness of COVID-19 mRNA vaccines in chronic kidney disease (CKD) individuals

Background: SARS-CoV-2 is a coronavirus that has rapidly spread across the world with a detrimental effect on the global population. Several reports have highlighted an increased mortality rate and a higher severity of COVID-19 infection in chronic kidney disease (CKD) individuals. Upon the development of various SARS-CoV-2 vaccines, mRNA vaccines including BNT162b2 and mRNA-1273 were deemed safe, with a high efficacy in preventing COVID-19 in the general population. This review investigates whether  SARS-CoV-2 mRNA vaccines are as effective in triggering an immune response in Dialysis Patients (DPs) and Kidney Transplant Recipients (KTRs) and if a third dose is required in this  population. Methods: A systematic search employing the PRISMA criteria was conducted in several major databases, with the data being extracted from publications for the period January 2021 to May 2022 (PROSPERO: CRD42022338514, June 15, 2022). Results: 80 studies were included in this analysis with a total cohort number of 15,059 participants. Overall, 85.29% (OR = 17.08, 95% CI = 15.84-18.42, I ² = 98%) and 41.06% (OR = 0.52, 95% CI = 0.48-0.5, I ² = 95%) of DPs and KTRs included in this review showed positive seroconversion after two doses of either mRNA vaccine, respectively. A total 76% (OR = 6.53, 95% CI = 5.63-7.5, I ² = 96%) of the cohort given a third dose of an mRNA vaccine demonstrated positive seroconversion, with 61.86% (OR = 2.31, 95% CI = 1.95-2.75 I ² = 95%) of the cohort that was assessed for a cellular response displaying a positive response. Conclusions: This data emphasises a reduced incidence of a positive immune response in DPs and KTRs compared to healthy controls, albeit a better response in DPs than when compared to KTRs alone was observed. A third dose  appears to increase the occurrence of an immune response in the overall DP/KTR cohort.

What Is New in Prophylaxis and Treatment of COVID-19 in Renal Transplant Patients? A Report from an ESOT Meeting on the Topic

I should highlight that this manuscript is not a formal review on the topic, but a report from an ESOT meeting held on 22 June 2022. The assumption of immunosuppressants exposes kidney transplant recipients to the risk of infections, including COVID-19 infection. A transplant patient having COVID-19 infection raises several questions, including whether the immunosuppressive therapy should be reduced with the consequent risk of favoring acute rejections. Patient vaccination before transplantation is probably the gold standard to avoid the risk of COVID-19 infection after transplantation. In the case of transplant patients, three measures may be undertaken: vaccination, use of monoclonal antibodies and use of therapeutic antiviral small molecules. Concerning vaccination, it is still debated which one is the best and how many doses should be administered, particularly considering the new variants of the virus. The onset of virus variants has stimulated researchers to find new active vaccines. In addition, not all transplant patients develop antibodies. An alternative prophylactic measure to be principally used for patients that do not develop antibodies after vaccination is the use of monoclonal antibodies. These drugs may be administered as prophylaxis or in the early stage of the disease. Finally, the small antiviral molecules may be used again as prophylaxis or treatment. Their major drawbacks are their interference with immunosuppressive drugs and the fact that some of them cannot be administered to patients with low eGFR.

The Effect of a Booster Dose mRNA Vaccine on COVID-19 Infection in Kidney Transplant Recipients after Inactivated or Viral Vector Vaccine Immunization

The mortality rate after novel coronavirus infection, which causes severe acute respiratory distress syndrome (SARS-CoV-2), is much higher in kidney transplant recipients (KTRs) compared to the general population. Seroconversion after vaccination is also lower, and breakthrough infection is much higher. Many studies reported seroconversion rate after a booster (third) dose of vaccine but clinical outcomes received less attention. Here, we reported the impact of an mRNA vaccine booster dose on clinical outcomes of KTRs with SARS-CoV-2 infection. A total of 183 KTRs with SARS-CoV-2 infection were identified. Of 183 KTRs, 146 KTRs had sufficient data for analysis and were included in this study. Forty-eight patients (32.9%) received zero to 1 doses of vaccine (Group 1), thirty-one (21.2%) received two doses (Group 2), and sixty-seven (45.9%) received a booster dose (Group 3). Pneumonia developed in 50%, 23%, and 10% in Group 1, 2, and 3 (p < 0.001). Hospital admission requirement was 81%, 48%, and 12% (p < 0.001). Mortality rate was 26%, 3%, and 3% (p = 0.001). A multivariate analysis showed that only diabetes adversely affects mortality while the booster dose of the vaccine significantly reduced mortality. The booster dose of the vaccine is strongly recommended in all KTRs especially those with diabetes. Our study also suggested the timing of the booster dose vaccine to be administered within 4 months after the second dose.

Antibody titers after a third dose of the SARS-CoV-2 BNT162b2 vaccine in immunocompromised adults in Greece: Is a fourth dose necessary?

Real‐world data suggest that protection against COVID‐19 declines a few months after vaccination, particularly in the elderly and immunocompromised individuals. Our study aimed to analyze the humoral response induced by a third supplemental dose of BNT162b2 vaccine in a mixed group of immunocompromised individuals by determining anti‐spike (anti‐S) IgG antibody titers at baseline (pre‐third vaccine dose) and 4 weeks after the dose. Serum samples were obtained from a total group of 85 immunocompromised individuals (history of cancer: n = 20, lymphoma: n = 4, leukemia: n = 3, transplant recipients: n = 4, autoimmune disease: n = 42, inflammatory disease: n = 6, autoimmune diabetes type 1: n = 6) all of whom had previously received a two‐dose schedule of the vaccine. The average number of days between second and third dose was 139.6145 (±41.39071). The overall IgG GMCs 4 weeks postvaccination were increased by more than 35 times (fold change = 35.30, p < 0.001). Fold changes were not significantly correlated with underlying condition, age, sex nor with days between second and third dose. Considering the predominance of omicron variants in the current period and the results of studies showing a decrease in the effectiveness of the third dose after 10 weeks we highly recommend a fourth dose to this vulnerable population group.