A prospective, comparative study of the immune response to inactivated influenza vaccine in pediatric liver transplant recipients and their healthy siblings

Hepatitis A vaccine immunogenicity among seronegative liver transplanted children

The hepatitis A virus (HAV) vaccine is highly immunogenic in general, yet data on its use in liver-transplanted (LT) children is limited. This study aimed to determine the seroimmunity to HAV in all LT children, and the immunogenicity of an inactivated HAV vaccine in seronegative LT children at King Chulalongkorn Memorial Hospital. Seronegative LT children received the inactivated HAV vaccine at 0 and 6-8 months with adverse events monitored for 3 days post-immunization. The result reviewed that among 105 LT children, vaccination records were available for 81%, of which 7.1% and 16.5% with one and two doses of HAV vaccine were immunized before transplantation, respectively. Post-transplantation, 20.1% were seropositive for HAV, with 9.5% due to pre-transplant immunization. Eighty-three seronegative LT children (aged 7.25 ± 4.40 years; 48.6% male) received two vaccine doses. The seropositive rate increased following the first and second doses and reached to 51.5%, and 92.9%, respectively (p < 0.001), with no serious adverse events reported. Age at vaccination and the interval from transplantation to vaccination were risk factors for non-responsiveness (p < 0.001). The study highlighted inadequate HAV vaccination coverage, leaving most LT children susceptible to infection. HAV vaccine proved highly immunogenic and safe, emphasizing the need for improved vaccination strategies before and after liver transplantation.Trial registration TCTR20220110001.

Patients with Obesity and a History of Metformin Treatment Have Lower Influenza Mortality: A Retrospective Cohort Study

Background: Obesity is a risk factor for the development of influenza by leading to a chronic inflammatory state and T-cell dysfunction. Based upon preclinical research, metformin has influenza activity by restoring T-cell function and improving the immune response. Objective: We aimed to evaluate the potential drug repurposing of metformin for the management of influenza among patients with obesity utilizing national claims data in an electronic health record database. Methods: The VA Informatics and Computing Infrastructure (VINCI) was utilized to obtain individual-level information on demographics, administrative claims, and pharmacy dispensation. A cohort was created among individuals with laboratory confirmed diagnosis of influenza with a diagnosis of fever, cough, influenza, or acute upper respiratory infection in an outpatient setting. The study outcome was death after diagnosis of influenza. Cohorts were formed using diabetes status and metformin exposure prior to a positive influenza diagnosis. Hazard ratios for mortality were estimated using a cox proportional hazards model adjusting for baseline covariates and a sub-analysis was conducted utilizing propensity score matching. A greedy nearest neighbor algorithm was utilized to match 1 to 1 non-metformin diabetic controls and non-diabetic controls to diabetic patients receiving metformin. Results: A total of 3551 patients met the inclusion criteria and were evaluated in our study. The cohorts consisted of 1461 patients in the non-diabetic cohort, 1597 patients in the diabetic / metformin cohort, and 493 patients in the diabetic no metformin cohort. Compared to non-diabetic patients, diabetic patients with metformin had a lower rate of death (aHR 0.78, 95% CI 0.609–0.999). There was not a statistical difference between the non-diabetic patients and the diabetic patients without metformin (aHR 1.046, 95% CI 0.781–1.400). The propensity score matched cohorts revealed consistent results with the primary analysis. Conclusion: Our results demonstrated patients with obesity and a history of metformin treatment have lower influenza mortality.

SARS-CoV-2 Vaccines: Safety and Immunogenicity in Solid Organ Transplant Recipients and Strategies for Improving Vaccine Responses

Purpose of Review

While solid organ transplant (SOT) recipients are at the highest risk for severe complications and increased mortality from COVID19 disease, their vaccination against SARS-CoV-2 remains challenging due to fear of immune-mediated adverse events and suboptimal immune response. Our current review is aimed to summarize current knowledge about the safety and efficacy of SARS-CoV-2 vaccines, describe factors that are correlated with immune response, and discuss strategies to improve vaccine immunogenicity in SOT recipients.

Recent Findings

SARS-CoV-2 vaccines are safe in SOT recipients and not related to rejection or other major adverse events. The immune response to two doses of vaccine is suboptimal and correlated to age and magnitude of immunosuppression. Administration of a third vaccine dose brings to significant amplification of immune response.

Summary

This review strengthens the existing recommendation of vaccination by three doses of vaccine in all SOT recipients and completion of vaccination before transplantation if possible.

Reduced humoral response to mRNA SARS-CoV-2 BNT162b2 vaccine in kidney transplant recipients without prior exposure to the virus

COVID-19 is associated with increased morbidity and mortality in transplant recipients. There are no efficacy data available regarding these patients with any of the available SARS-CoV-2 vaccines. We analyzed the humoral response following full vaccination with the BNT162b2 (Pfizer-BioNTech) in 136 kidney transplant recipients, and compared it to 25 controls. In order to exclude prior exposure to the virus, only participants with negative serology to SARS-CoV-2 nucleocapsid protein were included. All controls developed a positive response to spike protein, while only 51 of 136 transplant recipients (37.5%) had positive serology (p < .001). Mean IgG anti-spike level was higher in the controls (31.05 [41.8] vs. 200.5 [65.1] AU/mL, study vs. control, respectively, p < .001). Variables associated with null humoral response were older age (odds ratio 1.66 [95% confidence interval 1.17-2.69]), high-dose corticosteroids in the last 12 months (1.3 [1.09-1.86]), maintenance with triple immunosuppression (1.43 [1.06-2.15]), and regimen that includes mycophenolate (1.47 [1.26-2.27]). There was a similar rate of side effects between controls and recipients, and no correlation was found between the presence of symptoms and seroconversion. Our findings suggest that most kidney transplant recipients remain at high risk for COVID-19 despite vaccination. Further studies regarding possible measures to increase recipient's response to vaccination are required.

Persistent hypogammaglobulinemia in pediatric solid organ transplant recipients

INTRODUCTION

Hypogammaglobulinemia has not been well studied in pediatric solid organ transplant (SOT) recipients. We evaluated plasma immunoglobulin (Ig) and lymphocyte phenotypes among 31 pediatric heart and kidney recipients for two years post-transplant and from 10 non-transplanted children.

METHODS

Plasma IgM, IgG, and IgA were quantified by immunoturbidimetric assays, IgG subclasses were quantified by bead-based multiplex immunoassay, and lymphocyte phenotypes were assessed by flow cytometry.

RESULTS

Median age at transplant for SOT recipients was similar to that of the control cohort (15 vs. 12.5 years, respectively; P = .61). Mean plasma IgG and IgM levels for SOT recipients fell significantly below the control cohort means by 1 month post-transplant (P < .001 for both) and remained lower than control levels at 12-18 months post-transplant. Heart recipients had lower frequencies of a CD4⁺ naïve T lymphocytes relative to kidney recipients.

CONCLUSIONS

Hypogammaglobulinemia was prevalent and persistent among pediatric SOT recipients and may be secondary to immunosuppressive medications, as well as loss of thymus tissue and CD45RA⁺   CD4⁺ T cells in heart recipients. Limitations of our study include but are not limited to small sample size from a single center, lack of samples for all participants at every time point, and lack of peripheral blood mononuclear cell samples for the non-transplanted cohort.

Cytomegalovirus Viremia in Renal Transplant Recipients After Influenza Vaccination

Vaccination with the inactivated influenza vaccine is routinely recommended for all patients before and after transplant, with reduction in complications noted in transplant recipients. The vaccine is relatively well tolerated with few mild side effects. Cytomegalovirus (CMV) infection can reactivate in both solid organ transplant and hematopoietic stem cell transplant recipients, with some patients progressing to disease. There are multiple factors known to contribute to reactivation and subsequent CMV disease, however vaccination has not been reported as a specific risk factor.

We report on two renal transplant recipients who were seen to develop CMV viremia and CMV disease after receiving the Influenza vaccine. We review the literature regarding viremia occurring after vaccination in HIV patients (a similar group of immunocompromised patients).

Incidence of Hospitalization for Vaccine-Preventable Infections in Children Following Solid Organ Transplant and Associated Morbidity, Mortality, and Costs

IMPORTANCE

Pediatric transplant recipients are at risk for vaccine-preventable infections owing to immunosuppression, suboptimal response to vaccines before and after transplant, and potential underimmunization if transplant occurred early in life. However, the incidence and burden of illness from vaccine-preventable infections in this population is unknown.

OBJECTIVES

To evaluate in pediatric solid organ transplant recipients the number of hospitalizations for vaccine-preventable infections in the first 5 years after transplant and to determine the associated morbidity, mortality, and costs.

DESIGN, SETTING, AND PARTICIPANTS

A retrospective cohort study from January 1, 2004, to December 31, 2011, with 5 years of follow-up per participant (unless they died during the study period). The participants of this multicenter study through the Pediatric Health Information System were solid organ transplant recipients who were younger than 18 years at the time of transplant. Analysis began in July 2017.

EXPOSURES

Transplant.

MAIN OUTCOMES AND MEASURES

Hospitalizations for a vaccine-preventable infection during the first 5 years after transplant were ascertained using International Classification of Diseases, Ninth Revision, and International Statistical Classification of Diseases and Related Health Problems, Tenth Revision, clinical modification diagnosis codes. Data were collected on clinical care, outcomes, and costs during these hospitalizations.

RESULTS

Of 6980 transplant recipients identified, there were 3819 boys (54.7%), and the mean (SD) age at transplant was 8 (6.2) years. Overall, 1092 patients (15.6%) had a total of 1471 cases of vaccine-preventable infections. There were 187 of 1471 cases (12.7%) that occurred during transplant hospitalization. The case fatality rate was 1.7% for all infections. Excluding infections that occurred during transplant hospitalization (when all patients go to the intensive care unit), 213 of 1257 patients (17.0%) were hospitalized with a vaccine-preventable infection requiring intensive care. In multivariable analysis, age younger than 2 years at time of transplant and receipt of a lung, heart, intestine, or multivisceral organ were positively associated with increased risk of a hospitalization from a vaccine-preventable infection.Transplant hospitalizations complicated by vaccine-preventable infections were $120 498 more expensive (median cost) than transplant hospitalizations not complicated by vaccine-preventable infections.

CONCLUSIONS AND RELEVANCE

Hospitalization for vaccine-preventable infections occurred in more than 15% of solid organ transplant recipients in the first 5 years after transplant at a rate of up to 87 times higher than in the general population. There was significant morbidity, mortality, and costs from these infections, demonstrating the importance of immunizing all transplant candidates and recipients. Further research on improving immunization delivery, preventing nosocomial infections, and monitoring response to vaccines in the transplant population is needed.

Vaccines in pediatric transplant recipients-Past, present, and future

Infections significantly impact outcomes for solid organ and hematopoietic stem cell transplantation in children. Vaccine-preventable diseases contribute to morbidity and mortality in both early and late posttransplant time periods. Several infectious diseases and transplantation societies have published recommendations and guidelines that address immunization in adult and pediatric transplant recipients. In many cases, pediatric-specific studies are limited in size or quality, leading to recommendations being based on adult data or mixed adult-pediatric studies. We therefore review the current state of evidence for selected immunizations in pediatric transplant recipients and highlight areas for future investigation. Specific attention is given to studies that enrolled only children.

Obesity Impairs the Adaptive Immune Response to Influenza Virus

Influenza, a highly contagious respiratory tract infection, affects millions of adults and children each year. Several high-risk populations include children, the elderly, the immunocompromised, and recently the obese. Given the dramatic rise in obesity over the past few decades, this increased risk for influenza infection poses a serious public health threat because nearly 500 million adults and children worldwide are classified as obese. Obesity impairs the immune response to influenza and influenza vaccination through alterations of the cellular immune system. Compared with vaccinated healthy-weight adults, vaccinated obese adults have twice the risk of influenza or influenza-like illness despite equal serological response to vaccination. This challenges the current standard of protection for influenza and suggests that further vaccination methods or therapeutics are required to combat this virulent respiratory virus.

Does vaccination in solid-organ transplant recipients result in adverse immunologic sequelae? A systematic review and meta-analysis

BACKGROUND

Clinical guidelines recommend vaccinations for solid-organ transplant recipients. However, concern exists that vaccination may stimulate adverse alloimmune responses.

METHODS

We systematically reviewed the published literature regarding this aspect of vaccine safety. Electronic databases were searched for interventional and observational studies assessing de novo donor-specific antibodies (DSA) and rejection episodes after vaccination against infectious pathogens. Graft loss was also assessed. A meta-analysis was conducted for prospective, controlled studies. PRISMA reporting guidelines were followed.

RESULTS

Ninety studies (15,645 vaccinated patients and 42,924 control patients) were included. Twelve studies included control groups. The incidence of de novo DSA (14 studies) was 23 of 1,244 patients (1.85%) at 21 to 94 days. The incidence of rejection (83 studies) was 107 episodes in 5,116 patients (2.1%) at 0.7 to 6 months. Meta-analysis of prospective controlled studies (n = 8) showed no increased rejection risk with vaccination compared with no vaccination (RR 1.12, 95% CI 0.75 to 1.70). This finding was supported by data from 3 registry analyses.

CONCLUSIONS

Although the current evidence lacks high-quality, controlled studies, the currently available data provide reassurance that clinicians should recommend appropriate vaccination for their transplant patients as the risk of de novo DSA and rejection is relatively low.

Obesity Impairs the Adaptive Immune Response to Influenza Virus

Influenza, a highly contagious respiratory tract infection, affects millions of adults and children each year. Several high-risk populations include children, the elderly, the immunocompromised, and recently the obese. Given the dramatic rise in obesity over the past few decades, this increased risk for influenza infection poses a serious public health threat because nearly 500 million adults and children worldwide are classified as obese. Obesity impairs the immune response to influenza and influenza vaccination through alterations of the cellular immune system. Compared with vaccinated healthy-weight adults, vaccinated obese adults have twice the risk of influenza or influenza-like illness despite equal serological response to vaccination. This challenges the current standard of protection for influenza and suggests that further vaccination methods or therapeutics are required to combat this virulent respiratory virus.

Hospitalizations for Respiratory Syncytial Virus and Vaccine-Preventable Infections in the First 2 Years After Pediatric Liver Transplant

OBJECTIVES

To examine in liver transplant recipients at centers participating in the Pediatric Health Information System dataset the number of hospitalizations for respiratory syncytial virus (RSV) and vaccine-preventable infections (VPIs) in the first 2 years after transplantation, morbidity and mortality associated with these hospitalizations, and costs associated with these hospitalizations.

STUDY DESIGN

A retrospective cohort study of patients <18 years of age who underwent liver transplantation at a Pediatric Health Information System center between January 1, 2004, and December 31, 2012. Hospitalizations for RSV/VPIs during the first 2 years post-transplant were ascertained using International Classification of Diseases, Ninth Revision, Clinical Modification diagnosis codes. Data were collected on clinical care, outcomes, and costs during these hospitalizations.

RESULTS

There were 2554 liver transplant recipients identified; 415 patients (16.3%) had 544 cases of RSV/VPIs. RSV, rotavirus, and influenza were the most common infections resulting in hospitalization. Ninety-two patients (3.6%) had RSV/VPI during their transplant hospitalization. Transplant hospitalizations complicated by RSV/VPI were longer (44 days vs. 21 days; P < .001), had higher rejection rates (37% vs. 26%; P = .02), and were more expensive ($259 697 vs. $190 860; P < .001). Multivariate analyses identified age <2 years at transplant (P < .001) and multivisceral recipient (P = .04) as predictors of a hospitalization for RSV.

CONCLUSIONS

VPIs occurred in 1 of 6 liver transplant recipients in the first 2 years post-transplant, a significantly higher rate than in the general pediatric population. These hospitalizations had substantial morbidity, mortality, and costs, demonstrating the importance of vaccinating patients before transplantation.

Humoral, T-cell and B-cell immune responses to seasonal influenza vaccine in solid organ transplant recipients receiving anti-T cell therapies

BACKGROUND

We analyzed the impact of the anti-T-cell agents basiliximab and antithymocyte globulins (ATG) on antibody and cell-mediated immune responses after influenza vaccination in solid-organ transplant recipients.

METHODS

71 kidney and heart transplant recipients (basiliximab [n=43] and ATG [n=28]) received the trivalent influenza vaccine. Antibody responses were measured at baseline and 6 weeks post-vaccination by hemagglutination inhibition assay; T-cell responses were measured by IFN-γ ELISpot assays and intracellular cytokine staining (ICS); and influenza-specific memory B-cell (MBC) responses were evaluated using ELISpot.

RESULTS

Median time of vaccination from transplantation was 29 months (IQR 8-73). Post-vaccination seroconversion rates were 26.8% for H1N1, 34.1% for H3N2 and 4.9% for influenza B in the basiliximab group and 35.7% for H1N1, 42.9% for H3N2 and 14.3% for influenza B in the ATG group (p=0.44, p=0.61, and p=0.21, respectively). The number of influenza-specific IFN-γ-producing cells increased significantly after vaccination (from 35 to 67.5 SFC/10(6) PBMC, p=0.0007), but no differences between treatment groups were observed (p=0.88). Median number of IgG-MBC did not increase after vaccination (H1N1, p=0.94; H3N2 p=0.34; B, p=0.79), irrespective of the type of anti-T-cell therapy.

CONCLUSIONS

After influenza vaccination, a significant increase in antibody and T-cell immune responses but not in MBC responses was observed in transplant recipients. Immune responses were not significantly different between groups that received basiliximab or ATG.

Annual influenza vaccination reduces total hospitalization in patients with chronic hepatitis B virus infection: A population-based analysis

BACKGROUND

This study evaluated hospitalization and mortality in patients with chronic hepatitis B virus infection (HBV (+)) and matched comparison patients after stratifying the patients according to annual influenza vaccination (Vaccine (+)).

METHODS

Data from Taiwan's National Health Insurance program from 2000 to 2009 were used to identify HBV(+)/vaccine(+) (n=4434), HBV(+)/Vaccine(-) (n=3646), HBV(-)/Vaccine(+) (n=8868), and HBV(-)/Vaccine(-) (n=8868) cohorts. The risk of pneumonia/influenza, respiratory failure, intensive care, hospitalization, and mortality in the four cohorts was evaluated.

RESULTS

The total hospitalization rate was significantly lower in patients with chronic HBV infection who received an annual influenza vaccination than in chronic HBV-infected patients who did not receive an influenza vaccination (16.29 vs. 24.02 per 100 person-years), contributing to an adjusted hazard ratio (HR) of 0.56 (95% confidence interval (CI)=0.50-0.62). The HBV(+)/Vaccine(+) cohort also had lower risks than the HBV(+)/Vaccine(-) cohort for pneumonia and influenza (adjusted HR=0.79, 95% CI=0.67-0.92), intensive care unit admission (adjusted HR=0.33, 95% CI=0.25-0.43), and mortality (adjusted HR=0.19, 95% CI=0.15-0.24).

CONCLUSIONS

Our results suggest that annual influenza vaccination can reduce the risk of hospitalization and mortality in patients with chronic HBV infection.

Randomized, double-blind comparison of standard-dose vs. high-dose trivalent inactivated influenza vaccine in pediatric solid organ transplant patients

Children who have undergone SOT mount a lower immune response after vaccination with TIV compared to healthy controls. HD or SD TIV in pediatric SOT was given to subjects 3-17 yr and at least six months post-transplant. Subjects were randomized 2:1 to receive either the HD (60 μg) or the SD (15 μg) TIV. Local and systemic reactions were solicited after each vaccination, and immune responses were measured before and after each vaccination. Thirty-eight subjects were enrolled. Mean age was 11.25 yr; 68% male, 45% renal, 26% heart, 21% liver, 5% lung, and 5% intestinal. Twenty-three subjects were given HD and 15 SD TIV. The median time since transplant receipt was 2.2 yr. No severe AEs or rejection was attributed to vaccination. The HD group reported more tenderness and local reactions, fatigue, and body ache when compared to the SD cohort, but these were considered mild and resolved within three days. Subjects in the HD group demonstrated a higher percentage of four-fold titer rise to H3N2 compared to the SD group. HD influenza vaccine was well tolerated and may have increased immunogenicity. A phase 2 trial is needed to confirm.

Clinical and immune responses to inactivated influenza A(H1N1)pdm09 vaccine in children

BACKGROUND

As the influenza A H1N1 pandemic emerged in 2009, children were found to experience high morbidity and mortality and were prioritized for vaccination. This multicenter, randomized, double-blind, age-stratified trial assessed the safety and immunogenicity of inactivated influenza A(H1N1)pdm09 vaccine in healthy children aged 6 months to 17 years.

METHODS

Children received 2 doses of approximately 15 or 30 µg hemagglutin antigen 21 days apart. Reactogenicity was assessed for 8 days after each dose, adverse events through day 42, and serious adverse events or new-onset chronic illnesses through day 201. Serum hemagglutination inhibition titers were measured on days 0 (prevaccination), 8, 21, 29 and 42.

RESULTS

A total of 583 children received the first dose and 571 received the second dose of vaccine. Vaccinations were generally well-tolerated and no related serious adverse events were observed. The 15 µg dosage elicited a seroprotective hemagglutination inhibition (≥ 1:40) in 20%, 47% and 93% of children in the 6-35 month, 3-9 year and 10-17 year age strata 21 days after dose 1 and in 78%, 82% and 98% of children 21 days after dose 2, respectively. The 30 µg vaccine dosage induced similar responses.

CONCLUSIONS

The inactivated influenza A(H1N1)pdm09 vaccine exhibited a favorable safety profile at both dosage levels. While a single 15 or 30 µg dose induced seroprotective antibody responses in most children 10-17 years of age, younger children required 2 doses, even when receiving dosages 4- to 6-fold higher than recommended. Well-tolerated vaccines are needed that induce immunity after a single dose for use in young children during influenza pandemics.

2013 IDSA clinical practice guideline for vaccination of the immunocompromised host

An international panel of experts prepared an evidenced-based guideline for vaccination of immunocompromised adults and children. These guidelines are intended for use by primary care and subspecialty providers who care for immunocompromised patients. Evidence was often limited. Areas that warrant future investigation are highlighted.

Immunogenicity of pandemic influenza A H1N1/2009 adjuvanted vaccine in pediatric solid organ transplant recipients

The aim of this study was to assess the immunogenicity of a vaccine against this virus in a prospective cohort of transplanted pediatric patients without previous influenza infection who received one dose of MF59®-adjuvanted pandemic H1N1/2009 vaccine. Seventeen patients who were being regularly followed up at the Outpatient Clinic of the Children's Transplant Unit (liver and kidney transplantation) in Hospital Universitari Vall d'Hebron (Barcelona) were included. Seroconversion was demonstrated in 15 of 17 (88.2%) vaccinated children. There were no rejection episodes or major adverse events. The MF59(®) -adjuvanted pandemic H1N1/2009 vaccine was safe and elicited an adequate response.

Management of influenza infection in solid-organ transplant recipients: consensus statement of the Group for the Study of Infection in Transplant Recipients (GESITRA) of the Spanish Society of Infectious Diseases and Clinical Microbiology (SEIMC) and the Spanish Network for Research in Infectious Diseases (REIPI)

BACKGROUND

Solid organ transplant (SOT) recipients are at greater risk than the general population for complications and mortality from influenza infection.

METHODS

Researchers and clinicians with experience in SOT infections have developed this consensus document in collaboration with several Spanish scientific societies and study networks related to transplant management. We conducted a systematic review to assess the management and prevention of influenza infection in SOT recipients. Evidence levels based on the available literature are given for each recommendation. This article was written in accordance with international recommendations on consensus statements and the recommendations of the Appraisal of Guidelines for Research and Evaluation II (AGREE II).

RESULTS

Recommendations are provided on the procurement of organs from donors with suspected or confirmed influenza infection. We highlight the importance of the possibility of influenza infection in any SOT recipient presenting upper or lower respiratory symptoms, including pneumonia. The importance of early antiviral treatment of SOT recipients with suspected or confirmed influenza infection and the necessity of annual influenza vaccination are emphasized. The microbiological techniques for diagnosis of influenza infection are reviewed. Guidelines for the use of antiviral prophylaxis in inpatients and outpatients are provided. Recommendations for household contacts of SOT recipients with influenza infection and health care workers in close contact with transplant patients are also included. Finally antiviral dose adjustment guidelines are presented for cases of impaired renal function and for pediatric populations.

CONCLUSIONS

The latest scientific information available regarding influenza infection in the context of SOT is incorporated into this document.

Pediatric influenza vaccination: understanding the T-cell response

Influenza A virus-specific T cells are highly cross-reactive and contribute to heterosubtypic immunity, which may afford protection against novel pandemic strains of influenza virus. However, the magnitude and nature of virus-specific T-cell responses induced by natural infections and/or vaccination in young children is poorly understood. Host factors, such as the development of the immune system during childhood and environmental factors such as exposure rates to influenza viruses and interference by vaccination contribute to shaping the magnitude and specificity of the T-cell response. Here, the authors review several of these factors, including the differences between T-cell responses of young children and adults, the age-dependent frequency of virus-specific T cells and the impact of annual childhood influenza vaccination. In addition, the authors summarize all currently available studies in which influenza vaccine-induced T-cell responses were evaluated. The authors discuss these findings in the light of developing vaccines and vaccination strategies aiming at the induction of protective immunity to seasonal and pandemic influenza viruses of antigenically distinct subtypes.

Low seroconversion after one dose of AS03-adjuvanted H1N1 pandemic influenza vaccine in solid-organ transplant recipients

BACKGROUND

Immunocompromised individuals are more susceptible to complications produced by influenza infection. As a result, solid-organ transplant (SOT) recipients were targeted as a priority group to receive AS03-adjuvanted H1N1 influenza vaccine during 2009.

OBJECTIVE

To evaluate seroconversion after one dose of adjuvanted pandemic influenza H1N1 (pH1N1) vaccine in SOT recipients.

METHODS

Adult SOT recipients were enrolled to receive one 3.75 μg dose of adjuvanted pH1N1 vaccine. Serological status was tested using a hemagglutination inhibition assay before and two and four weeks postvaccination.

RESULTS

The five SOT recipients (one liver, two kidney and two lung transplants) had a median age of 50 years (range 36 to 53 years), and three were male, who were a median time of three years (range two months to 15 years) post-transplant. All patients were on a double or triple immunosuppressive regimen. The prevaccination pH1N1 titre was 1:10 in four patients and 1:40 in one patient. Seroprotection was observed only in one patient, with a rise in titre from 1:40 at baseline to 1:320 at both two and four weeks after vaccination. This lung transplant recipient had documented previous infection with pH1N1.

CONCLUSION

Results of the present small study call into question whether one dose of adjuvanted pH1N1 vaccine can provide seroprotection in SOT recipients.

Respiratory viral infections in pediatric solid organ and hematopoietic stem cell transplantation

Respiratory viruses are common in children, including pediatric recipients of both solid organ transplantation and hematopoietic stem cell transplantation. The prevalence and risk factors in each of these groups are reviewed. Furthermore, associated morbidity and mortality in pediatric transplant recipients with respiratory viral infections are addressed. The literature on specific prevention and treatment options for respiratory syncytial virus, adenovirus, influenza, and other respiratory viruses in pediatric solid organ and hematopoietic stem cell transplant recipients is reported.

Influenza vaccination for immunocompromised patients: systematic review and meta-analysis by etiology

Many national guidelines recommend annual influenza vaccination of immunocompromised patients, although the decision to vaccinate is usually at clinical discretion. We conducted a systematic review and meta-analyses to assess the evidence for influenza vaccination in this group, and we report our results by etiology. Meta-analyses showed significantly lower odds of influenza-like illness after vaccination in patients with human immunodeficiency virus (HIV) infection, patients with cancer, and transplant recipients and of laboratory-confirmed influenza in HIV-positive patients, compared with patients receiving placebo or no vaccination. Pooled odds of seroconversion and seroprotection were typically lower in HIV-positive patients, patients with cancer, and transplant recipients, compared with immunocompetent controls. Vaccination was generally well tolerated, with variation in mild adverse events between etiological groups. Limited evidence of a transient increase in viremia and a decrease in the percentage of CD4(+) cells in HIV-positive patients was found although not accompanied by worsening of clinical symptoms. Clinical judgment remains important when discussing the benefits and safety profile with immunocompromised patients.

Humoral and cell-mediated immune responses to monovalent 2009 influenza A/H1N1 and seasonal trivalent influenza vaccines in high-risk children

OBJECTIVE

Humoral and cell-mediated immune responses to monovalent 2009 pandemic influenza A (H1N1/2009) and seasonal trivalent influenza (TIV) vaccines were evaluated in healthy children and children with asthma, sickle cell disease (SCD), systemic lupus erythematosus (SLE), and solid organ transplantation (SOT).

STUDY DESIGN

Blood was collected from 112 subjects at the time of H1N1/2009 vaccination and 46 ± 15 days later for hemagglutination inhibition titers and γ-interferon ELISPOT responses to H1N1/2009 vaccine and TIV; unvaccinated children also received TIV at enrollment.

RESULTS

A significant increase in the percentage of subjects with seroprotective hemagglutination inhibition titers to both vaccines was observed in all high-risk groups. Children with asthma and SCD were most likely to achieve seroprotective titers to H1N1/2009, whereas <50% of subjects with SOT and SLE had a seroprotective response. Subjects with SOT and SLE also had lower rates of seroprotection after TIV, and subjects with SLE had the lowest ELISPOT responses to both vaccines. Overall, 73% of healthy children exhibited protective responses to TIV; only 35% achieved seroprotection for H1N1/2009.

CONCLUSIONS

This evaluation of immune responses to H1N1/2009 in high-risk children suggests suboptimal responses for SOT and SLE subjects, but not for subjects with SCD or asthma. Higher antigen dose, additional dose regimens, or both for immunocompromised children warrant further investigation.

Influenza vaccination for immunocompromised patients: systematic review and meta-analysis from a public health policy perspective

BACKGROUND

Immunocompromised patients are vulnerable to severe or complicated influenza infection. Vaccination is widely recommended for this group. This systematic review and meta-analysis assesses influenza vaccination for immunocompromised patients in terms of preventing influenza-like illness and laboratory confirmed influenza, serological response and adverse events.

METHODOLOGY/PRINCIPAL FINDINGS

Electronic databases and grey literature were searched and records were screened against eligibility criteria. Data extraction and risk of bias assessments were performed in duplicate. Results were synthesised narratively and meta-analyses were conducted where feasible. Heterogeneity was assessed using I(2) and publication bias was assessed using Begg's funnel plot and Egger's regression test. Many of the 209 eligible studies included an unclear or high risk of bias. Meta-analyses showed a significant effect of preventing influenza-like illness (odds ratio [OR]=0.23; 95% confidence interval [CI]=0.16-0.34; p<0.001) and laboratory confirmed influenza infection (OR=0.15; 95% CI=0.03-0.63; p=0.01) through vaccinating immunocompromised patie nts compared to placebo or unvaccinated controls. We found no difference in the odds of influenza-like illness compared to vaccinated immunocompetent controls. The pooled odds of seroconversion were lower in vaccinated patients compared to immunocompetent controls for seasonal influenza A(H1N1), A(H3N2) and B. A similar trend was identified for seroprotection. Meta-analyses of seroconversion showed higher odds in vaccinated patients compared to placebo or unvaccinated controls, although this reached significance for influenza B only. Publication bias was not detected and narrative synthesis supported our findings. No consistent evidence of safety concerns was identified.

CONCLUSIONS/SIGNIFICANCE

Infection prevention and control strategies should recommend vaccinating immunocompromised patients. Potential for bias and confounding and the presence of heterogeneity mean the evidence reviewed is generally weak, although the directions of effects are consistent. Areas for further research are identified.

Influenza vaccination in the organ transplant recipient: review and summary recommendations

Influenza virus causes a spectrum of illness in transplant recipients with a high rate of lower respiratory disease. Seasonal influenza vaccination is an important public health measure recommended for transplant recipients and their close contacts. Vaccine has been shown to be safe and generally well tolerated in both adult and pediatric transplant recipients. However, responses to vaccine are variable and are dependent on various factors including time from transplantation and specific immunosuppressive medication. Seasonal influenza vaccine has demonstrated safety and no conclusive evidence exists for a link between vaccination and allograft dysfunction. Annually updated trivalent inactivated influenza vaccines have been available and routinely used for several decades, although newer influenza vaccination formulations including high-dose vaccine, adjuvanted vaccine, quadrivalent inactivated vaccine and vaccine by intradermal delivery system are now available or will be available in the near future. Safety and immunogenicity data of these new formulations in transplant recipients requires investigation. In this document, we review the current state of knowledge on influenza vaccines in transplant recipients and make recommendations on the use of vaccine in both adult and pediatric organ transplant recipients.

Immune response to pandemic H1N1 2009 influenza a vaccination in pediatric liver transplant recipients

After the announcement of a worldwide pandemic in June 2009, a single dose of a monovalent pandemic H1N1 2009 influenza A (pH1N1/09) vaccine was advocated for all Australians who were 10 years and older because of excellent immunogenicity trial results for healthy children and adults. Immunocompromised patients have previously been shown to have lower seroconversion rates after routine vaccinations. There is a lack of data concerning the immune response of this patient group after pH1N1/09 vaccination. The aim of this study was to assess the immunogenicity of a pH1N1/09 vaccine in pediatric liver transplant recipients 10 years of age or older. Liver transplant recipients ≥ 10 years were prospectively recruited. All participants were administered a single intramuscular injection of the pH1N1/09 vaccine (15 μg). Serum antibody levels were determined by hemagglutination immediately before and ≥ 6 weeks after vaccination. Clinical and laboratory data (age, time since transplantation, immunosuppression, and lymphocyte counts) were analyzed comparing seroconverters and nonconverters with the Student's t test. A second dose of the vaccine was offered to all those who displayed no seroprotective titers after the first vaccination. Antibody levels were again determined 6 weeks later. Twenty-one of 28 liver transplant patients completed the study. The seroconversion rate was 62% after the first dose and 89.5% after the second dose. At baseline, 7 of 21 patients (33.4%) were already seropositive. Increasing time since transplantation positively correlated with successful seroconversion. In conclusion, a single dose of a pandemic influenza A vaccine does not elicit a reliable immune response in adolescent pediatric liver transplant patients. A second dose of the vaccine is warranted in this group of patients, at least in a pandemic scenario. There is an urgent need to further assess vaccine strategies in this high-risk group.

Antibody response to influenza vaccine in pediatric liver transplant recipients

BACKGROUND

Data on the immunogenicity of the influenza vaccine in children after liver transplantation are sparse. Our study aims to evaluate the response of such patients to the trivalent influenza vaccine, administered by different protocols in 2 influenza seasons.

METHODS

Children attending the Liver Transplantation Unit of a tertiary care medical center were prospectively recruited and immunized with the inactivated subvirion influenza vaccine during the influenza seasons of 2004/2005 (1 dose, n = 18) and 2005/2006 (2 doses 4-6 weeks apart, n = 32). Antibodies were measured by hemagglutination inhibition assay. Immunity was defined as a titer of ≥1:40, and response was defined as a ≥4-fold increase in antibody titer from baseline.

RESULTS

In 2004/2005, the proportions of patients with protective antibodies were similar before and after 1 dose of vaccine. We found significant difference after the first dose for the A/H3N2 Wisconsin strain (43.2% vs. 70.3%, P = 0.003) and B/Malaysia strains (8.1% vs. 35.1%, P = 0.003) and for A/H1N1 New Caledonia strain (48.6% vs. 64.9% vs. 75%, P = 0.08, 0.005, respectively) after the second dose in 2005/2006 season. In 2004/2005, geometric mean titers rose significantly (P = 0.03) for the A/H3N2 New York strain; in 2005/2006, geometric mean titers for A/H3N2 New York and B/Malaysia increased after the first dose and for A/H1N1 New Caledonia after the second dose. Antibody titers were unrelated to age at transplantation, time from transplantation, and number of immunosuppressive drugs used. No serious vaccine-related events were documented.

CONCLUSIONS

Liver-transplanted children respond to influenza vaccination. For some strains, the response is similar to that reported for healthy children. A second vaccine dose yielded no statistically significant benefit.

Impaired cellular immune response to diphtheria and tetanus vaccines in children after thoracic transplantation

Safety and immunogenicity of diphtheria and tetanus booster vaccination were evaluated in 28 children after thoracic transplantation. Adverse events were documented in a patient diary. Blood was collected prior to and four wk after vaccination. Specific antibody concentrations were measured by ELISA. Lymphocytes were investigated for expression of activation markers (CD25, HLA-DR) by flow cytometry and proliferation assays with and without stimulation. Post-vaccination antibody titers were higher than prevaccination (p < 0.001), with more patients having protective antibody levels against diphtheria (p < 0.02) and tetanus (p < 0.001). There was no increased proliferation in non-stimulated or stimulated cultures after vaccination. The number of T-lymphocytes activated by the vaccination antigens was similar pre- and post-vaccination, whereas HLA-DR-expression on stimulated and non-stimulated CD4(+) T-cells increased significantly. Increase in antibodies was negatively correlated with tacrolimus dose, and impaired cellular immunity was associated with higher tacrolimus dose and steroid use. Adverse events were similar to the general population; serious adverse events and rejection did not occur. Vaccination with inactivated vaccines can be performed safely in immunosuppressed children after thoracic transplantation and induces protective antibody levels in the majority of patients. Impaired induction of specific cellular immunity is correlated with intensity of immunosuppression and may explain reduced sustainability of antibodies.

Early post-transplant vaccination with pandemic influenza A/H1N1 vaccine in pediatric heart transplant recipients

Pandemic influenza A/H1N1 virus has the potential to cause severe disease in pediatric transplant patients. A pandemic vaccine against H1N1 is effective in immunocompetent children. We investigated the immunogenicity of this vaccine when given in the first six months after heart transplantation. Four patients younger than two yr received two doses of vaccine and one patient older than seven yr received one dose. Titers were obtained using the HAI at baseline and after final immunization. Five patients were enrolled, ages 0.5-7 yr. Median age at the time of transplant was five months (range 3 wk-7 yr). All patients received induction with anti-thymoglobulin and maintenance immunosuppression with tacrolimus, MMF, and prednisone. Patients were immunized with the adjuvanted H1N1 vaccine after heart transplant at median time of nine wk (range 5-23 wk) post-transplant. Three of five developed protective titers against H1N1. A proportion of pediatric patients may respond to influenza vaccine even when immunized in the early post-transplant period.

Acceptance and adverse events of the 2009 H1N1 vaccination in immunosuppressed pediatric liver transplant recipients

A retrospective analysis of H1N1 vaccination in 127 children at ≥ 1 year after liver transplantation found only moderate acceptance (56%) of the vaccination. Physical adverse events were of moderate severity, but frequent (74%). Protection against infection was good, with infection rates of 4% in vaccinated children versus 25% in nonvaccinated children.

Effectiveness and safety of inactivated influenza vaccination in pediatric liver transplant recipients over three influenza seasons

Annual influenza vaccination is recommended for pediatric liver transplant recipients, who are at high risk of influenza-related complications. However, effectiveness and safety of vaccination may differ among influenza seasons in this population and have not been fully evaluated. Subjects comprised 38 pediatric liver transplant recipients with or without influenza vaccination through the 2006-2007, 2007-2008 and 2008-2009 influenza seasons. Recipients received inactivated trivalent (AH1/AH3/B) influenza vaccine, and comparisons were made to non-vaccinated recipients with regard to effectiveness and safety. No significant differences were seen between recipient groups for acute allograft rejection, acute febrile illness, or influenza virus infection. No serious systemic adverse events were observed in vaccinated recipients. Seroprotection rate (defined as the proportion of recipients with HI antibody titer ≥ 1:40), seroconversion rate (proportion of recipients with a ≥ 4-fold increase in HI titers), and geometric mean titers were mostly elevated after vaccination for the three influenza antigens in each season. These three indicators of immunogenicity showed similar results in both vaccinated recipients and vaccinated healthy children in the 2007-2008 season. These findings suggest that pediatric liver transplant patients may respond safely to inactivated seasonal influenza vaccines in a similar manner to healthy children, and effectiveness varies among influenza seasons.

The cellular immune response to influenza vaccination is preserved in rheumatoid arthritis patients treated with rituximab

OBJECTIVES

Yearly vaccination against influenza is currently recommended to patients with rheumatoid Arthritis (RA). Antibody and cell-mediated responses are both involved in the defense against influenza. Humoral responses to influenza vaccine are impaired in RA patients treated with rituximab (RTX). The objectives of this study were to comparatively assess cell mediated and humoral responses to influenza vaccination in RA patients with or without RTX-induced CD20 B-cell depletion.

METHODS

Trivalent influenza subunit vaccine was administered to 46 RA patients and to 16 healthy controls. The RA group included 29 patients treated by RTX and 17 on conventional disease-modifying anti-rheumatic drugs (DMARDs), mostly methotrexate. Peripheral blood mononuclear cells and sera were obtained immediately before and 4-6 weeks after vaccination. Cell-mediated response to influenza antigens was evaluated by flow cytometry for activated CD4 T-cells. Humoral response was evaluated by haemagglutination inhibition assay.

RESULTS

Cellular response: Cell-mediated responses were comparable in RTX-treated vs. DMARDs-treated patients. The recall postvaccination CD4+ cellular response was similar in RA patients and healthy controls. A positive correlation was found between CD19+ cell count on the day of vaccination and cellular response in RTX-treated RA patients. Humoral response: The antibody response rate was significantly impaired in the RTX group: being 26.4%, 68.4% and 47.1% in RTX-treated, DMARDs-treated and controls, respectively.

CONCLUSION

Cellular immunity to influenza vaccination in RTX-treated patients was similar to DMARDs-treated patients and healthy controls, while humoral immunity was severely impaired. The preservation of cellular immunity may explain the relatively low rate of infection among B-cell depleted patients.

Prevention and treatment of infectious complications after solid organ transplantation in children

Effective prevention, diagnosis, and treatment of infectious diseases after transplantation are key factors contributing to the success of organ transplantation. Most transplant patients experience different kinds of infections during the first year after transplantation. Children are at particular risk of developing some types of infections by virtue of lack of immunity although they may be at risk for other types due the effect of immunosuppressive regimens necessary to prevent rejection. Direct consequences of infections result in syndromes such as mononucleosis, pneumonia, gastroenteritis, hepatitis, among other entities. Indirect consequences are mediated through cytokines, chemokines, and growth factors elaborated by the transplant recipient in response to microbial replication and invasion, which contribute to the net state of immunosuppression among other effects. This review summarizes the major infections that occur after pediatric organ transplantation, highlighting the current treatment and prevention strategies, based on the available data and/or consensus.

Guidance on novel influenza A/H1N1 in solid organ transplant recipients

Novel influenza A/H1N1 virus has caused significant illness worldwide. In response to this global crisis, the American Society of Transplantation (AST) Infectious Diseases Community of Practice and the Transplant Infectious Diseases section of The Transplantation Society (TTS) developed a guidance document for novel H1N1. In this paper, we discuss current guidance for H1N1 as it relates to solid organ transplantation. We include discussion around clinical presentation, diagnosis, therapy and prevention specifically addressing areas such as chemoprophylaxis, immunization and donor-derived infection. Although this document addresses conditions specific to novel H1N1, many principles could be applied to future pandemics. As new information emerges about novel H1N1, updates will be made to the electronic version of the document posted on the websites of the AST and TTS.

Prophylaxis against pulmonary viral and fungal infections in solid organ transplant recipients

Pulmonary viral and fungal infections in solid organ transplant recipients are one of the most common and potentially life-threatening infections. Understanding the strategies used for prophylaxis and prevention of these infections is critical for the health and well-being of transplant recipients. Prophylactic measures range from simple patient education to complex chemoprophylactic interventions; however, a multifaceted approach is most often required. This article focuses on strategies to prevent pulmonary viral and fungal infections in transplant recipients, with an emphasis on recent evidence that may influence practice guidelines.

Update on infectious diseases in pediatric solid organ transplantation

PURPOSE OF REVIEW

Numerous recent advances have been made in the field of infectious diseases and pediatric solid organ transplant.

RECENT FINDINGS

Although many studies contain somewhat small cohorts of individuals, when summarized together they contribute significantly to our knowledge about pediatric solid organ transplant, especially regarding risk factors for infection, management of BK virus nephropathy, the use of live viral vaccines, and consideration for rare infections as well as donor-derived infections.

SUMMARY

In sum, these recent advances in infection in the field of pediatric solid organ transplant will help decrease infection, thus improving morbidity and mortality, as well as transplant outcomes, especially by decreasing direct (graft injury) and indirect (immune upregulation) effects on organ transplantation. This review will focus on recent advances in the field of infectious diseases in pediatric solid organ transplant by highlighting some of the most important and interesting articles in the field within the past few years.