Effectiveness of first, second, and third COVID-19 vaccine doses in solid organ transplant recipients: A population-based cohort study from Canada

Coping With COVID-19: Perspectives of Caregivers of Children and Young People With Chronic Kidney Disease

BACKGROUND

Caregivers of children and young people with chronic kidney disease (CKD) face challenging circumstances on a daily basis; however, the difficulties they experienced during the COVID-19 pandemic, as well as potentially positive experiences, are not yet fully understood. The aim of this study was to explore the pandemic-related experiences of these caregivers.

METHODS

Twelve caregivers were recruited from a hospital-based pediatric renal program; eight families were posttransplant. Caregivers participated in virtual semistructured interviews conducted between March 2021 and November 2022. They provided responses to open-ended questions concerning how the pandemic affected their child with CKD, their family, and themselves. Interviews were transcribed and coded using thematic analysis.

RESULTS

Four main themes were identified: (1) Family Life, which included disruptions in routine, reduced social supports, and changes in the quality of family relationships; (2) Mental Health and Coping, which included increased anxiety and positive coping strategies; (3) Work and School Life, which included changes to work and school; and (4) Health and Health Care Systems, which included virtual health care and public health restrictions.

CONCLUSIONS

Despite facing profound challenges, caregivers identified both positive and negative aspects of their pandemic experiences. Their coping strategies highlighted individual and family resilience characteristics. Implications for health care providers, including future pandemic planning, support for the transition from in-person to virtual care, and strategies to better address barriers to resources for families of children with chronic kidney disease were discussed.

Comparison of COVID-19 Hospitalization and Death Between Solid Organ Transplant Recipients and the General Population in Canada, 2020-2022

Background

Solid organ transplant recipients have a high risk of severe outcomes from SARS-CoV-2 infection. A comprehensive understanding of the impact of the COVID-19 pandemic across multiple waves in the solid organ transplant population and how this compares to the general population is limited. We conducted a population-based cohort study using linked administrative healthcare databases from Ontario, Canada to answer this question.

Methods

We included 15 306 solid organ transplant recipients and 12 160 904 individuals from the general population. Our primary outcome was the rate (per 100 person-years) of severe COVID-19 (ie, hospitalization or death with a positive SARS-CoV-2 test) occurring between January 25, 2020, and November 30, 2022.

Results

Compared with the general population, solid organ transplant recipients had almost a 6 times higher rate of severe COVID-19 (20.39 versus 3.44 per 100 person-years), with almost 5.5 times as high a rate of death alone (4.19 versus 0.77 per 100 person-years). Transplant recipients with severe COVID-19 were substantially younger (60.1 versus 66.5 y) and had more comorbidities. The rate of severe COVID-19 declined over time in the solid organ transplant population, with an incidence rate of 41.25 per 100 person-years in the first wave (January 25, 2020, to August 31, 2020) and 18.41 in the seventh wave (June 19, 2022, to November 30, 2022, Omicron era).

Conclusions

Solid organ transplant recipients remain at high risk of severe outcomes when they are infected with SARS-CoV-2. Resources and strategies to mitigate the impact of SARS-CoV-2 exposure are needed in this vulnerable patient population.

Repeated COVID-19 Vaccination Drives Memory T- and B-cell Responses in Kidney Transplant Recipients: Results From a Multicenter Randomized Controlled Trial

BACKGROUND

Insight into cellular immune responses to COVID-19 vaccinations is crucial for optimizing booster programs in kidney transplant recipients (KTRs).

METHODS

In an immunologic substudy of a multicenter randomized controlled trial (NCT05030974) investigating different repeated vaccination strategies in KTR who showed poor serological responses after 2 or 3 doses of an messenger RNA (mRNA)-based vaccine, we compared SARS-CoV-2-specific interleukin-21 memory T-cell and B-cell responses by enzyme-linked immunosorbent spot (ELISpot) assays and serum IgG antibody levels. Patients were randomized to receive: a single dose of mRNA-1273 (100 μg, n = 25), a double dose of mRNA-1273 (2 × 100 μg, n = 25), or a single dose of adenovirus type 26 encoding the SARS-CoV-2 spike glycoprotein (Ad26.COV2.S) (n = 25). In parallel, we also examined responses in 50 KTR receiving 100 μg mRNA-1273, randomized to continue (n = 25) or discontinue (n = 25) mycophenolate mofetil/mycophenolic acid. As a reference, the data were compared with KTR who received 2 primary mRNA-1273 vaccinations.

RESULTS

Repeated vaccination increased the seroconversion rate from 21% to 66% in all patients, which was strongly associated with enhanced levels of SARS-CoV-2-specific interleukin-21 memory T cells (odd ratio, 3.84 [1.89-7.78]; P < 0.001) and B cells (odd ratio, 35.93 [6.94-186.04]; P < 0.001). There were no significant differences observed in these responses among various vaccination strategies. In contrast to KTR vaccinated with 2 primary vaccinations, the number of antigen-specific memory B cells demonstrated potential for classifying seroconversion after repeated vaccination (area under the curve, 0.64; 95% confidence interval, 0.37-0.90; P = 0.26 and area under the curve, 0.95; confidence interval, 0.87-0.97; P < 0.0001, respectively).

CONCLUSIONS

Our study emphasizes the importance of virus-specific memory T- and B-cell responses for comprehensive understanding of COVID-19 vaccine efficacy among KTR.

Beyond prevention: Unveiling the benefits of triple vaccination on COVID-19 severity and resource utilization in solid organ transplant recipients

OBJECTIVE

Despite the widespread reduction in COVID-19-related morbidity and mortality attributed to vaccination in the general population, vaccine efficacy in solid organ transplant recipients (SOTR) remains under-characterized. This study aimed to investigate clinically relevant outcomes on double and triple-vaccinated versus unvaccinated SOTR with COVID-19.

STUDY DESIGN AND SETTING

A retrospective propensity score-matched cohort study was performed utilizing data from the US Collaborative Network Database within TriNetX (n = 117,905,631). We recruited vaccinated and unvaccinated (matched controls) SOTR with COVID-19 over two time periods to control for vaccine availability: December 2020 to October 2022 (bi-dose, double-dose vaccine effectiveness) and December 2020 to April 2023 (tri-dose, triple-dose vaccine effectiveness). A total of 42 factors associated with COVID-19 disease severity were controlled for including age, obesity, diabetes, and hypertension. We monitored 30-day outcomes including acute respiratory failure, intubation, and death following a diagnosis of COVID-19.

RESULTS

Subjects were categorized into two cohorts based on the two time periods: bi-dose cohort (vaccinated, n = 462; unvaccinated, n = 20,998); tri-dose cohort (vaccinated, n = 517; unvaccinated, n = 23,061).Compared to unvaccinated SOTR, 30-day mortality was significantly lower for vaccinated subjects in both cohorts: tri-dose (2.0% vs 7.5%, HR = 0.22 [95% CI: 0.11, 0.46]); bi-dose (3.7% vs 8.2%, HR = 0.43 [95% CI: 0.24, 0.76]). Hospital admission rates were similar between bi-dose vaccinated and unvaccinated subjects (33.1% vs 28.6%, HR = 1.2 [95% CI: 0.95, 1.52]). In contrast, tri-dose vaccinated subjects had a significantly lower likelihood of hospital admission (29.4% vs 36.6%, HR = 0.74 [95% CI: 0.6, 0.91]). Intubation rates were significantly lower for triple-vaccinated- (2.3% vs 5.2%, p < 0.05), but not double-vaccinated subjects (3.0% vs 5.2%, p > 0.05).

CONCLUSION

In solid organ transplant recipients with COVID-19, triple vaccination, but not double vaccination, against SARS-CoV-2 was associated with significantly less hospital resource utilization, decreased disease severity, and fewer short-term complications. These real-world data from extensively matched controls support the protective effects of COVID-19 vaccination with boosters in this vulnerable population.

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.

Risk of Severe COVID-19 and Protective Effectiveness of Vaccination Among Solid Organ Transplant Recipients

BACKGROUND

Solid organ transplant recipients (SOTRs) are at higher risk for severe infection. However, the risk for severe COVID-19 and vaccine effectiveness among SOTRs remain unclear.

METHODS

This retrospective study used a nationwide health care claims database and COVID-19 registry from the Republic of Korea (2020 to 2022). Adult SOTRs diagnosed with COVID-19 were matched with up to 4 non-SOTR COVID-19 patients by propensity score. Severe COVID-19 was defined as treatment with high-flow nasal cannulae, mechanical ventilation, or extracorporeal membrane oxygenation.

RESULTS

Among 6783 SOTRs with COVID-19, severe COVID-19 was reported with the highest rate in lung transplant recipients (13.16%), followed by the heart (6.30%), kidney (3.90%), and liver (2.40%). SOTRs had a higher risk of severe COVID-19 compared to non-SOTRs, and lung transplant recipients showed the highest risk (adjusted odds ratio, 18.14; 95% confidence interval [CI], 8.53-38.58). Vaccine effectiveness against severe disease among SOTRs was 47% (95% CI, 18%-65%), 64% (95% CI, 49%-75%), and 64% (95% CI, 29%-81%) for 2, 3, and 4 doses, respectively.

CONCLUSIONS

SOTRs are at significantly higher risk for severe COVID-19 compared to non-SOTRs. Vaccination is effective in preventing the progression to severe COVID-19. Efforts should be made to improve vaccine uptake among SOTRs, while additional protective measures should be developed.

Systems biology of B cells in COVID-19

The integration of multi-'omic datasets into complex systems-wide assessments has become a mainstay in immunologic investigation. This focus on high-dimensional data collection and analysis was on full display in the investigation of COVID-19, the respiratory illness resulting from infection by the novel coronavirus SARS-CoV-2. Particularly in the area of B cell biology, tremendous efforts in both cellular and serologic investigation have resulted in an increasingly detailed mapping of the coordinated effector, memory, and antibody secreting cell responses that underpin the development of humoral immunity in response to primary viral infection. Further, the rapid development and deployment of effective vaccines has allowed for the assessment of developing memory responses across a wide variety of immune contexts, including in patients with compromised immune function. The result has been a period of rapid gains in the understanding of B cell biology unrestricted to the study of COVID-19. Here, we outline the systems-level technologies that have been routinely implemented in these investigations throughout the pandemic, and discuss how their use has led to clear and applicable gains in pursuance of the amelioration of human infectious disease and beyond.

Incidence and Severity of COVID-19 in Relation to Anti-Receptor-Binding Domain IgG Antibody Level after COVID-19 Vaccination in Kidney Transplant Recipients

Kidney transplant recipients (KTRs) elicit an impaired immune response after COVID-19 vaccination; however, the exact clinical impact remains unclear. We therefore analyse the relationship between antibody levels after vaccination and the risk of COVID-19 in a large cohort of KTRs. All KTRs living in the Netherlands were invited to send a blood sample 28 days after their second COVID-19 vaccination for measurement of their IgG antibodies against the receptor-binding domain of the SARS-CoV-2 spike protein (anti-RBD IgG). Information on COVID-19 was collected from the moment the blood sample was obtained until 6 months thereafter. Multivariable Cox and logistic regression analyses were performed to analyse which factors affected the occurrence and severity (i.e., hospitalization and/or death) of COVID-19. In total, 12,159 KTRs were approached, of whom 2885 were included in the analyses. Among those, 1578 (54.7%) became seropositive (i.e., anti-RBD IgG level >50 BAU/mL). Seropositivity was associated with a lower risk for COVID-19, also after adjusting for multiple confounders, including socio-economic status and adherence to COVID-19 restrictions (HR 0.37 (0.19-0.47), p = 0.005). When studied on a continuous scale, we observed a log-linear relationship between antibody level and the risk for COVID-19 (HR 0.52 (0.31-0.89), p = 0.02). Similar results were found for COVID-19 severity. In conclusion, antibody level after COVID-19 vaccination is associated in a log-linear manner with the occurrence and severity of COVID-19 in KTRs. This implies that if future vaccinations are indicated, the aim should be to reach for as high an antibody level as possible and not only seropositivity to protect this vulnerable patient group from disease.

Effectiveness of a Fourth COVID-19 mRNA Vaccine Dose Against the Omicron Variant in Solid Organ Transplant Recipients

BACKGROUND

The effectiveness of booster doses of COVID-19 vaccines in solid organ transplant recipients is unclear. We conducted a population-based matched cohort study using linked administrative healthcare databases from Ontario, Canada to estimate the marginal vaccine effectiveness of a fourth versus third dose of the BNT162b2 and mRNA-1273 vaccines against clinically important outcomes (ie, hospitalization or death) and infection during the era of the Omicron variant.

METHODS

We matched 3120 solid organ transplant recipients with a third COVID-19 vaccine dose (reference) to 3120 recipients with a fourth dose. Recipients were matched on the third dose date (±7 d). We used a multivariable Cox proportional hazards model to estimate the marginal vaccine effectiveness with outcomes occurring between December 21, 2021 and April 30, 2022.

RESULTS

The cumulative incidence of COVID-19-related hospitalization or death was 2.8% (95% confidence interval [CI], 2.0-3.7) in the third dose group compared with 1.1% (95% CI, 0.59-1.8) in the fourth dose group after 84 d of follow-up (P < 0.001). The adjusted marginal vaccine effectiveness was 70% (95% CI, 47-83) against clinically important outcomes and 39% (95% CI, 21-52) against SARS-CoV-2 infection.

CONCLUSIONS

Compared with a third dose, a fourth dose of the COVID-19 vaccine was associated with improved protection against hospitalization, death, and SARS-CoV-2 infection during the Omicron era. Results highlight the importance of a booster COVID-19 vaccine dose in solid organ transplant recipients.

B and T Cell Responses to SARS-CoV-2 Vaccination in Kidney and Liver Transplant Recipients with and without Previous COVID-19

(1) Background: Vulnerable populations including transplant recipients are jeopardised by COVID-19. Herein, we report on B and T cell responses among liver and kidney organ recipients at our centre. (2) Methods: 23 liver and 45 kidney (14 thereof combined kidney/pancreas) transplanted patients were vaccinated with two doses of BNT162b2 followed by a booster dose of mRNA-1273 in 28 non-responders 4 months thereafter. Anti-SARS-CoV-2-Ig was measured by specific ELISA and virus neutralisation assay; T cell responses were measured by a spike protein-specific IFN-γ release assay. (3) Results: Compared to controls, B and T cell responses were weak in transplant recipients, particularly in those without prior exposure to SARS-CoV-2. Within this group, only 15% after the first and 58.3% after the second vaccination achieved seroconversion. A total of 14 out of 28 vaccination non-responders achieved a seroconversion after a third dose. Vaccination side effects were more frequent in healthy controls. The use of mycophenolate was associated with reduced anti-SARS-CoV-2-Ig production. (4) Conclusions: Our data confirm that vaccination responses are insufficient after standard vaccination in liver and kidney transplant recipients and are affected to a variable degree by specific immunosuppressants, particularly mycophenolate. Monitoring vaccination success and re-vaccinating those who are unresponsive seems prudent to achieve sufficient titres. Overall, prospective large-scale, multinational, multicentre studies or high-quality meta-analyses will be needed to generate personalised vaccination strategies in order to achieve protective immunity in high-risk, hard-to-immunize populations.

Immunologic response and seroconversion following third-dose COVID-19 vaccination in solid organ transplant recipients: A meta-analysis

INTRODUCTION

The immunogenicity and efficacy of COVID-19 vaccination varied by demographic, including solid organ transplant recipients on immunosuppressive therapy.

AIM

This purpose of this study is to assess seropositivity and seroconversion in solid-organ transplant recipients before and after third-dose COVID-19 vaccination.

METHODS

This study is a systematic review and meta-analysis performed using PRISMA guidelines. To analyze clinical and cohort studies reporting immunologic response and seroconversion third-dose vaccination, a systematic search was performed using electronic databases (PubMed, Scopus, Cochrane, Directory of Open Access Journal (DOAJ), and Clinicaltrials.gov).

RESULT

There were 18 full-text papers that could be analyzed qualitatively and quantitatively. After the third vaccination, the pooled rate seropositivity was 67.00% (95% CI 59.511; 74.047, I2 = 93.82%), and the pooled rate seroconversion was 52.51% (95% CI 44.03; 60.91, I2 = 92.15%). The pooled rate of seroconversion after the mRNA-based booster was 52.380% (95% CI 40.988; 63.649, I2 = 94.35%), and after the viral-vector-based booster was 42.478% (95% CI 35.222; 49.900, I2 = 0.00%).

CONCLUSION

Based on the analysis of immunologic responses and seroconversion findings, the third-dose vaccination of solid organ transplant recipients is an effective method in establishing better immunity against COVID-19.

The role of interleukin-21 in COVID-19 vaccine-induced B cell-mediated immune responses in patients with kidney disease and kidney transplant recipients

T-cell-mediated help to B cells is required for the development of humoral responses, in which the cytokine interleukin (IL)-21 is key. Here, we studied the mRNA-1273 vaccine-induced SARS-CoV-2-specific memory T-cell IL-21 response, memory B cell response, and immunoglobulin (Ig)G antibody levels in peripheral blood at 28 days after the second vaccination by ELISpot and the fluorescent bead-based multiplex immunoassay, respectively. We included 40 patients with chronic kidney disease (CKD), 34 patients on dialysis, 63 kidney transplant recipients (KTR), and 47 controls. We found that KTR, but not patients with CKD and those receiving dialysis, showed a significantly lower number of SARS-CoV-2-specific IL-21 producing T cells than controls (P < .001). KTR and patients with CKD showed lower numbers of SARS-CoV-2-specific IgG-producing memory B cells when compared with controls (P < .001 and P = .01, respectively). The T-cell IL-21 response was positively associated with the SARS-CoV-2-specific B cell response and the SARS-CoV-2 spike S1-specific IgG antibody levels (both Pearson r = 0.5; P < .001). In addition, SARS-CoV-2-specific B cell responses were shown to be IL-21 dependent. Taken together, we show that IL-21 signaling is important in eliciting robust B cell-mediated immune responses in patients with kidney disease and KTR.

Update of the recommendations on the management of the SARS-CoV-2 coronavirus pandemic (COVID-19) in kidney transplant patients

SARS-CoV-2 infection (COVID-19) has had a significant impact on transplant activity in our country. Mortality and the risk of complications associated with COVID-19 in kidney transplant recipients (KT) were expected to be higher due to their immunosuppressed condition and the frequent associated comorbidities. Since the beginning of the pandemic in March 2020 we have rapidly improved our knowledge about the epidemiology, clinical features and management of COVID-19 post-transplant, resulting in a better prognosis for our patients. KT units have been able to adapt their programs to this new reality, normalizing both donation and transplantation activity in our country. This manuscript presents a proposal to update the general recommendations for the prevention and treatment of infection in this highly vulnerable population such as KT.

Reduction in the risk of progression of solid organ transplant recipients infected by SARS-CoV-2 treated with monoclonal antibodies

Recipients of solid organ transplants (SOT) are at higher risk of infection by SARS-CoV-2 virus especially due to chronic immunosuppression therapy and frequent multiple comorbid conditions. COVID-19 is a potentially life-threatening disease in SOT recipients, with an increased likelihood of progressing to severe disease, with the need of hospitalization, admission to the intensive care unit (ICU) and mechanical ventilatory support. This article presents an updated review of different aspects related to the outcome of COVID-19 in SOT recipients. In nvaccinated SOT recipients, COVID-19 is associated with a high mortality rate, in-patient care and ICU admission, and impaired graft function or rejection in severe disease. In vaccinated SOT recipients even after full vaccination, there is a reduction of the risk of mortality, but the course of COVID-19 may continue to be severe, influenced by the time from transplant, the net state of immunosuppression and having suffered graft rejection or dysfunction. SOT recipients develop lower immunity from mRNA vaccines with suboptimal response. Treatment with mAbs provides favorable outcomes in non-hospitalized SOT recipients at high risk for severe disease, with lower rates of hospitalization, emergency department visits, ICU care, progression to severe disease, and death. However, broad vaccination and therapeutic options are required, particularly in light of the tendency of the SARS-CoV-2 virus to adapt and evade both natural and vaccine-induced immunity.

Effect of COVID-19 Pandemic on Patients Who Have Undergone Liver Transplantation: Retrospective Cohort Study

BACKGROUND

In liver transplant (LT) recipients, immunosuppressive therapy may potentially increase the risk of severe COVID-19 and may increase the mortality in patients. However, studies have shown conflicting results, with various studies reporting poor outcomes while the others show no difference between the LT recipients and healthy population. The aim of this study is to determine the impact of the COVID-19 pandemic on survival of LT recipients.

METHODS

This is a retrospective cohort study analyzing the data from 387 LT recipients diagnosed with COVID-19. LT recipients were divided into two groups: survival (n = 359) and non-survival (n = 28) groups. A logistic regression model was used to determine the independent risk factors for mortality. Machine learning models were used to analyze the contribution of independent variables to the mortality in LT recipients.

RESULTS

The COVID-19-related mortality rate in LT recipients was 7.2%. Multivariate analysis showed that everolimus use (p = 0.012; OR = 6.2), need for intubation (p = 0.001; OR = 38.4) and discontinuation of immunosuppressive therapy (p = 0.047; OR = 7.3) were independent risk factors for mortality. Furthermore, COVID-19 vaccination reduced the risk of mortality by 100 fold and was the single independent factor determining the survival of the LT recipients.

CONCLUSION

The effect of COVID-19 infection on LT recipients is slightly different from the effect of the disease on the general population. The COVID-19-related mortality is lower than the general population and vaccination for COVID-19 significantly reduces the risk of mortality.

Protective Effect of Vaccine Doses and Antibody Titers Against SARS-CoV-2 Infection in Kidney Transplant Recipients

Patients undergoing kidney transplantation have a poor response to vaccination and a higher risk of disease progression of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). The effectiveness of vaccine doses and antibody titer tests against the mutant variant in these patients remains unclear. We retrospectively analyzed the risk of SARS-CoV-2 infection in a single medical center according to vaccine doses and immune responses before the outbreak. Among 622 kidney transplant patients, there were 77 patients without vaccination, 26 with one dose, 74 with two doses, 357 with three, and 88 with four doses. The vaccination status and infection rate proportion were similar to the general population. Patients undergoing more than three vaccinations had a lower risk of infection (odds ratio = 0.6527, 95% CI = 0.4324-0.9937) and hospitalization (odds ratio = 0.3161, 95% CI = 0.1311-0.7464). Antibody and cellular responses were measured in 181 patients after vaccination. Anti-spike protein antibody titer of more than 1,689.3 BAU/mL is protective against SARS-CoV-2 infection (odds ratio = 0.4136, 95% CI = 0.1800-0.9043). A cellular response by interferon-γ release assay was not correlated with the disease (odds ratio = 1.001, 95% CI = 0.9995-1.002). In conclusion, despite mutant strain, more than three doses of the first-generation vaccine and high antibody titers provided better protection against the omicron variant for a kidney transplant recipient.

Immunogenicity, Safety, and Breakthrough Severe Acute Respiratory Syndrome Coronavirus 2 Infections After Coronavirus Disease 2019 Vaccination in Organ Transplant Recipients: A Prospective Multicenter Canadian Study

Background

Solid organ transplant (SOT) recipients are at risk for severe coronavirus disease 2019 (COVID-19), despite vaccination. Our study aimed to elucidate COVID-19 vaccine immunogenicity and evaluate adverse events such as hospitalization, rejection, and breakthrough infection in a SOT cohort.

Methods

We performed a prospective, observational study on 539 adult SOT recipients (age ≥18 years old) recruited from 7 Canadian transplant centers. Demographics including transplant characteristics, vaccine types, and immunosuppression and events such as hospitalization, infection, and rejection were recorded. Follow ups occurred every 4-6 weeks postvaccination and at 6 and 12 months from first dose. Serum was processed from whole blood to measure anti-receptor binding domain (RBD) antibodies of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) spike protein to assess immunogenicity.

Results

The COVID-19 vaccines were found to be safe in SOT recipients with low rates of rejection requiring therapy (0.7%). Immunogenicity improved after the third vaccine dose, yet 21% developed no anti-RBD response. Factors such as older age, lung transplantation, chronic kidney disease, and shorter duration from transplant were associated with decreased immunogenicity. Patients with at least 3 doses were protected from hospitalization when experiencing breakthrough infections. Significantly increased anti-RBD levels were observed in patients who received 3 doses and had breakthrough infection.

Conclusions

Three or four doses of COVID-19 vaccines were safe, increased immunogenicity, and protected against severe disease requiring hospitalization. Infection paired with multiple vaccinations significantly increased anti-RBD response. However, SOT populations should continue to practice infection prevention measures, and they should be prioritized for SARS-CoV-2 pre-exposure prophylactics and early therapeutics.

COVID-19 Prevention in Solid Organ Transplant Recipients: Current State of the Evidence

Although COVID-19 vaccines are safe, most organ transplant recipients fail to mount an antibody response after two mRNA vaccines. Thus, three mRNA vaccines constitute a primary vaccine series after solid organ transplant. However, neutralizing antibodies after three or greater mRNA vaccines are lower against Omicron versus older variants. Predictors of attenuated responses include age, vaccination within 1 year from transplant, mycophenolate, and BNT162b2. Some seronegative transplant recipients exhibit durable T-cell responses. Vaccine effectiveness in transplants is lower than in the general population. Immunosuppression reduction around revaccination warrants further study. Monoclonal antibody pre-exposure prophylaxis may be protective against susceptible variants.

Vaccine Effectiveness Against the SARS-CoV-2 B.1.1.529 Omicron Variant in Solid Organ and Islet Transplant Recipients in England: A National Retrospective Cohort Study

BACKGROUND

The effectiveness of vaccines against the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) B.1.1.529 Omicron variant in immunosuppressed solid organ and islet transplant (SOT) recipients is unclear.

METHODS

National registries in England were linked to identify SARS-CoV-2 positive tests, noninjury hospitalization within 14 d, and deaths within 28 d between December 7, 2020, and March 31, 2022 in adult SOT recipients. Incidence rate ratios (IRRs) for infection, and hospitalization or death, were adjusted for recipient demographics and calendar month for the Omicron-dominant period (December 20, 2021, to March 31, 2022). Mortality risk following SARS-CoV-2 infection was adjusted for recipient demographics and dominant variant using a Cox proportional-hazards model for the entire time period.

RESULTS

During the Omicron-dominant period, infection IRRs (95% confidence intervals) were higher in those receiving 2, 3, and 4 vaccine doses than in unvaccinated patients (1.25 [1.08-1.45], 1.46 [1.28-1.67], and 1.79 [1.54-2.06], respectively). However, hospitalization or death IRRs during this period were lower in those receiving 3 or 4 vaccine doses than in unvaccinated patients (0.62 [0.45-0.86] and 0.39 [0.26-0.58], respectively). Risk-adjusted analyses for deaths after SARS-CoV-2 infection between December 7, 2020, and March 31, 2022, found hazard ratios (95% confidence intervals) of 0.67 (0.46-0.98), 0.46 (0.30-0.69), and 0.18 (0.09-0.35) for those with 2, 3, and 4 vaccine doses, respectively, when compared with the unvaccinated group.

CONCLUSIONS

In immunosuppressed SOT recipients, vaccination is associated with incremental, dose-dependent protection against hospitalization or death after SARS-CoV-2 infection, including against the Omicron variant.

[Update of the recommendations on the management of the SARS-CoV-2 coronavirus pandemic (COVID-19) in kidney transplant patients.]

SARS-CoV-2 infection (COVID-19) has had a significant impact on transplant activity in our country. Mortality and the risk of complications associated with COVID-19 in kidney transplant recipients (KT) were expected to be higher due to their immunosuppressed condition and the frequent associated comorbidities. Since the beginning of the pandemic in March 2020 we have rapidly improved our knowledge about the epidemiology, clinical features and management of COVID-19 post-transplant, resulting in a better prognosis for our patients. KT units have been able to adapt their programs to this new reality, normalizing both donation and transplantation activity in our country.This manuscript presents a proposal to update the general recommendations for the prevention and treatment of infection in this highly vulnerable population such as KT.

SARS-CoV-2 Vaccination in Solid-Organ Transplant Recipients

The coronavirus disease 2019 (COVID-19) pandemic has posed significant global challenges for solid organ transplant (SOT) recipients. Mortality rates of COVID-19 in this patient population remain high, despite new available therapeutic options and Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) vaccination. Priority access to SARS-CoV-2 vaccination for waitlisted candidates and for SOT patients and their family members is recommended since the advantage from vaccination reduces the risk of COVID-19-related complications. However, immunogenicity and efficacy of COVID-19 vaccines are lower in waitlisted candidates and SOT recipients than in the general population. Routine systematic assessment of humoral and cellular immune responses after SARS-CoV-2 vaccination is controversial, although highly recommended for investigation and improvement of knowledge. SOT recipients should continue to adhere to preventive protective measures despite vaccination and may undergo passive antibody prophylaxis. This article seeks to provide an update on SARS-CoV-2 vaccination and preventive measures in SOT recipients based on existing literature and international guidelines.

Humoral response after a third and fourth dose of mRNA-based SARS-CoV-2 vaccine in previously seronegative kidney transplant recipients

Growing evidence shows diminished response to mRNA-based SARS-CoV‑2 vaccination in kidney transplant recipients. We aimed to investigate the seroconversion rate after a 3rd and 4th dose of mRNA vaccination in kidney transplant recipients without prior antibody response to two or three vaccination doses.This retrospective study included 324 prevalent kidney transplant recipients of a single tertiary transplantation center of which 157 remained seronegative, defined as anti-spike-RBD-IgG antibody titer < 7.1 BAU/ml, after two doses of mRNA-based SARS-CoV‑2 vaccination. Maintenance immunosuppression was not changed. The median patient age was 60.6 years (IQR 51.4-68.1 years), 66.9% were male. Positivity for anti-spike-RBD-IgG (≥ 7.1 BAU/ml) was measured 4-5 weeks after administration of a 3rd and 4th vaccine dose.Seroconversion rates were 63.9% after a 3rd dose and 29.3% after a 4th dose of vaccine. Cumulative prevalence of seropositivity was 51.5% after 2 doses, 80.5% after 3 doses and 84.2% after 4 doses.In conclusion, seroconversion can be achieved in the majority of the kidney transplant recipients by administrating three or four doses of mRNA vaccine without changing maintenance immunosuppression.