Antibody persistence 1 year after pandemic H1N1 2009 influenza vaccination and immunogenicity of subsequent seasonal influenza vaccine among adult organ transplant patients

We investigated the antibody persistence in solid organ transplant (SOT) recipients 1 year after immunization with two doses of monovalent AS03‐adjuvanted influenza A(H1N1)pdm09 vaccine. We also assessed the boosting effect of the seasonal trivalent inactivated vaccine 2010 (TIV/10) that contained the influenza A(H1N1)pdm09 strain. A total of 49 SOT recipients and 11 healthy controls were included. After a blood sample was obtained to assess the persistent immunity, one dose of TIV/10 was administered and another blood sample was collected 1 month after vaccination. A(H1N1)pdm09 antibodies were measured using a haemagglutination inhibition assay. The percentage of SOT recipients with protective titres decreased between 1 month and 10–14 months after the monovalent influenza A(H1N1)pdm09 vaccination, from 79% (n = 38) to 47% (n = 23) (P = 0.02). The corresponding numbers for the control group were 100% and 63%, respectively (P = 0.008). After the TIV/10 boosting dose, the number of SOT recipients with protective titres increased from 47% (n = 23) to 71% (n = 35) (P = 0.2). All the controls reached a protective titre level. The median titre rise was significantly higher among controls when compared to SOT recipients (P = 0.0036). No rejection or adverse events were seen. The results show an obvious need for vaccine boosting doses in the SOT patients. (ClinicalTrials.gov number: NCT01256931).     

De Novo Anti‐HLA Antibody After Pandemic H1N1 and Seasonal Influenza Immunization in Kidney Transplant Recipients

In solid organ transplanted patients, annual influenza immunization is strongly recommended because of morbidity and mortality of influenza infections. In 2009, the rapid spread of a novel H1N1 influenza A virus led to the accelerated development of novel pandemic influenza vaccines. In Switzerland, the recipients received one dose of seasonal influenza and two doses of AS03‐adjuvanted H1N1 vaccines. This situation provided a unique opportunity to analyze the influence of novel adjuvanted influenza vaccines on the production of de novo anti‐HLA antibodies. We prospectively followed two independent cohorts including 92 and 59 kidney‐transplanted patients, assessing their anti‐HLA antibodies before, 6 weeks and 6 months after vaccination. Sixteen of 92 (17.3%) and 7 of 59 (11.9%) patients developed anti‐HLA antibodies. These antibodies, detected using the single antigen beads technology, were mostly at low levels and included both donor‐specific and non‐donor‐specific antibodies. In 2 of the 20 patients who were followed at 6 months, clinical events possibly related to de novo anti‐HLA antibodies were observed. In conclusion, multiple doses of influenza vaccine may lead to the production of anti‐HLA antibodies in a significant proportion of kidney transplant recipients. The long‐term clinical significance of these results remains to be addressed.     

Seasonal Maintenance of Influenza Vaccine-Induced Antibody Response in Kidney Transplant Recipients

Background/Aims: Although annual influenza vaccination is recommended for kidney transplant recipients, efficacy as reflected by serum antibody titers has not been well studied beyond 1 month in kidney transplant recipients. Methods: We performed a single-center prospective cohort study of 51 kidney transplant recipients and 102 healthy controls receiving the 2006-2007 influenza vaccine. Anti-hemagglutinin antibody titers to A/H1N1, A/H3N2, and B were measured before and 1 month after vaccination, and again at the end of influenza season. The primary outcome was the proportion of participants maintaining seroprotection (antibody titer ≥1:32) for the duration of the influenza season after influenza vaccination. Results: Median follow-up time was 175 and 155 days in the transplant and control groups, respectively. For types A/H1N1 and B, a similar high proportion of the transplant and control groups (88.5 and 81.6% vs. 83.7 and 74.2% for A/H1N1 and B, respectively) maintained seroprotection. For type A/H3N2, significantly less of the transplant group (66.7%) versus the control group (90%) maintained a protective influenza vaccine response (odds ratio 0.21, 95% confidence interval 0.07-0.64). This difference disappeared in adjusted analyses. Actual geometric mean titers decreased significantly within both groups (p < 0.001) but this did not differ between groups. Conclusions: Once they have developed protective vaccine-induced antibody responses to influenza vaccine, kidney transplant recipients are able to maintain adequate protective levels of antibody compared with healthy controls.     

Mycophenolate and lower graft function reduce the seroresponse of kidney transplant recipients to pandemic H1N1 vaccination

In late 2009 transplant organizations recommended that kidney recipients be vaccinated for pandemic H1N1 influenza (pH1N1); however, the vaccine efficacy was unknown. We had offered a monovalent non-adjuvanted pH1N1 vaccine to transplant recipients. Here we compared the pre- and post-vaccination seroresponses of 151 transplant recipients to that of 71 hemodialysis patients and 30 healthy controls. Baseline seroprotection was similar between groups but was significantly different at 1 month (44, 56, and 87%, respectively). Seroconversion was significantly less common for transplant recipients (32%) than dialysis patients (45%) and healthy controls (77%). After adjusting for age and gender, dialysis patients were significantly more likely (2.7-fold) to achieve new seroprotection than transplant recipients. The likelihood of seroprotection in transplant recipients was significantly reduced by mycophenolate use (adjusted odds ratio 0.24), in a dose-dependent manner, and by reduced eGFR (adjusted odds ratio 0.16 for worst to best). Seroprotection and geometric mean antibody titers increased substantially in 49 transplant recipients who subsequently received the 2010 seasonal influenza vaccine. Thus, patients requiring renal replacement therapy had reduced seroresponses to vaccination with the monovalent vaccine compared with healthy controls. Transplant recipient responses were further reduced if they were receiving mycophenolate or had significantly lower graft function.     

Heterologous Immune Responses to Influenza Vaccine in Kidney Transplant Recipients

Influenza vaccine is known to have suboptimal immunogenicity in transplant recipients. Despite this, influenza vaccine may have the added benefit of inducing a cross‐reactive immune response to viral strains not found in the vaccine. This is termed “heterologous immunity” and has not been assessed previously in transplant patients. Pre‐ and postvaccination sera from kidney transplant recipients (n = 60) immunized with the 2012–2013 adjuvanted or nonadjuvanted influenza vaccine underwent testing by hemagglutination inhibition assay for strains not present in vaccine: A/New Caledonia/20/99 (H1N1), A/Texas/50/2012 (H3N2) and B/Brisbane/60/2008. The geometric mean titer of antibody to heterologous strains increased after vaccine (H1N1: 80.0 to 136.1, p < 0.001; H3N2: 23.3 to 77.3, p < 0.001; B: 13.3 to 19.5, p < 0.001). Seroconversion rates were 16.7%, 41.7%, and 13.3%, respectively. No differences in heterologous response were seen in the adjuvanted versus nonadjuvanted groups. Patients were more likely to seroconvert for a cross‐reactive antigen if they seroconverted for the specific vaccine antigen. Seroconversion to heterologous A/H3N2, for example, was 84.0% for homologous H3N2 seroconverters versus 11.4% for nonseroconverters (p < 0.001). This study provides novel evidence that transplant recipients are able to mount significant cross‐protective responses to influenza vaccine that may be an additional, previously unknown benefit of immunization.     

Usefulness of a systematic approach at listing for vaccine prevention in solid organ transplant candidates

Solid organ transplant (SOT) candidates may not be immune against potentially vaccine‐preventable diseases because of insufficient immunizations and/or limited vaccine responses. We evaluated the impact on vaccine immunity at transplant of a systematic vaccinology workup at listing that included (1) pneumococcal with and without influenza immunization, (2) serology‐based vaccine recommendations against measles, varicella, hepatitis B virus, hepatitis A virus, and tetanus, and (3) the documentation of vaccines and serology tests in a national electronic immunization registry ( www.myvaccines.ch ). Among 219 SOT candidates assessed between January 2014 and November 2015, 54 patients were transplanted during the study. Between listing and transplant, catch‐up immunizations increased the patients’ immunity from 70% to 87% (hepatitis A virus, P = .008), from 22% to 41% (hepatitis B virus, P = .008), from 77% to 91% (tetanus, P = .03), and from 78% to 98% (Streptococcus pneumoniae, P = .002). Their immunity at transplant was significantly higher against S. pneumoniae (P = .006) and slightly higher against hepatitis A virus (P = .07), but not against hepatitis B virus, than that of 65 SOT recipients transplanted in 2013. This demonstrates the value of a systematic multimodal serology‐based approach of immunizations of SOT candidates at listing and the need for optimized strategies to increase their hepatitis B virus vaccine responses.     

Therapy With m‐TOR Inhibitors Decreases the Response to the Pandemic Influenza A H1N1 Vaccine in Solid Organ Transplant Recipients

Concern has been raised regarding the response to vaccination in solid organ transplant recipients (SOTR) undergoing immunosuppressant regimens and the possibility of rejection related to the immune response associated with pandemic influenza H1N1–2009 vaccination. The goal of this study was to assess the immunogenicity, efficacy and safety of the pandemic vaccine in SOTR. We performed a multicenter prospective study in SOTR receiving the pandemic vaccine. Immunological response was determined in serum 5 weeks after vaccination by microneutralization assays, and immunoglobulins were measured by ELISA. Three hundred and forty‐six SOTR were included. Preexisting seroprotection was detected in 13.6% of cases and rates of seroconversion and seroprotection after vaccination were 73.1% and 82.9%, respectively. Patients with baseline antibody titers had better geometric mean titers (GMT)‐post after pandemic vaccination (339.4 vs. 121.4, p < 0.001). Younger age, liver disease and m‐TOR inhibitor therapy were independently associated with lower seroprotection and GMT‐post. There were no major adverse effects or rejection episodes. Pandemic vaccine was safe in SOTR and elicited an adequate response, although lower than in healthy individuals. This is the first study describing a decreased response after vaccination in patients receiving mTOR inhibitors who presented lower seroprotection rates and lower GMT‐post.     

Randomized Controlled Trial of High‐Dose Intradermal Versus Standard‐Dose Intramuscular Influenza Vaccine in Organ Transplant Recipients

The immunogenicity of standard intramuscular (IM) influenza vaccine is suboptimal in transplant recipients. Also, recent studies suggest that alloantibody may be upregulated due to vaccination. We evaluated a novel high‐dose intradermal (ID) vaccine strategy. In conjunction, we assessed alloimmunity. Transplant recipients were randomized to receive IM or high‐dose ID vaccine. Strain‐specific serology and HLA alloantibody production was determined pre‐ and postimmunization. In 212 evaluable patients (105 IM, 107 ID), seroprotection to H1N1, H3N2 and B strains was 70.5%, 63.8% and 52.4% in the IM group, and 71.0%, 70.1%, 63.6% in the ID group (p = ns). Seroconversion to ≥1 antigen was 46.7% and 51.4% in the IM and ID groups respectively (p = 0.49). Response was more likely in those ≥6 months posttransplant (53.2% vs. 19.2%; p = 0.001). Use of mycophenolate mofetil was inversely associated with vaccine response in a dose‐dependent manner (p < 0.001). Certain organ subgroups had higher response rates for influenza B in the ID vaccine group. Differences in anti‐HLA antibody production were detected in only 3/212(1.4%) patients with no clinical consequences. High‐dose intradermal vaccine is an alternative to standard vaccine and has potential enhanced immunogenicity in certain subgroups. In this large cohort, we also show that seasonal influenza does not result in significant alloantibody production.     

Influenza vaccine after pediatric kidney transplant: a Midwest Pediatric Nephrology Consortium study

The main aim of this study was to compare the response to trivalent inactivated influenza vaccine in children who received a kidney transplant and were on steroid-free versus steroid-based immunosuppression. Groups: 1. Kidney transplant recipients on steroid-free immunosuppression (n = 27); 2. Kidney transplant recipients on steroid-based immunosuppression (n = 39); 3. Healthy controls (n = 21). Hemagglutination inhibition titers against 2007–2008 A/H1N1 and A/H3N2 and B strains were measured before and 8 weeks postvaccination. Postvaccination geometric mean titers to A/H1N1 were significantly lower among both transplant groups than controls (p = 0.025 and 0.015, respectively). Postvaccination titers to H3N2 and B strains were not statistically different between groups. Proportions of participants developing seroprotection were not different among groups. Both kidney transplant groups seroconverted less than controls for A/H1N1 (p = 0.0002) and were no different from controls for B. For A/H3N2, the steroid-free group had the weakest seroconversion (p = 0.008), possibly due to mycophenolate-enhanced exposure and a younger age. Overall, children after kidney transplantation demonstrated a good serologic response to the inactivated influenza vaccine although somewhat lower than controls. Steroid-free immunosuppression did not seem to present an advantage in antibody response. Data on inactivated influenza vaccine safety and efficacy was collected and demonstrated absence of acute rejection or laboratory-proven influenza for 6 months postvaccination.     

Natural influenza infection produces a greater diversity of humoral responses than vaccination in immunosuppressed transplant recipients

The humoral immune response to influenza virus infection is complex and may be different compared to the antibody response elicited by vaccination. We analyzed the breadth of IgG and IgA responses in solid organ transplant (SOT) recipients to a diverse collection of 86 influenza antigens elicited by natural influenza A virus (IAV) infection or by vaccination. Antibody levels were quantified using a custom antigen microarray. A total of 120 patients were included: 80 IAV infected (40 A/H1N1 and 40 A/H3N2) and 40 vaccinated. Based on hierarchical clustering analysis, infection with either H1N1 or H3N2 virus showed a more diverse antibody response compared to vaccination. Similarly, H1N1-infected individuals showed a significant IgG response to 27.9% of array antigens and H3N2-infected patients to 43.0% of antigens, whereas vaccination elicited a less broad immune response (7.0% of antigens). Immune responses were not exclusively targeting influenza hemagglutinin (HA) proteins but were also directed against conserved influenza antigens. Serum IgA responses followed a similar profile. This study provides novel data on the breadth of antibody responses to influenza. We also found that the diversity of response is greater in influenza-infected rather than vaccinated patients, providing a potential mechanistic rationale for suboptimal vaccine efficacy in this population.     

Influenza vaccination and humoral alloimmunity in solid organ transplant recipients

Annual influenza vaccination is recommended in solid organ transplant (SOT) recipients. However, concerns have been raised about the impact of vaccination on antigraft alloimmunity. We evaluated the humoral alloimmune responses to influenza vaccination in a cohort of SOT recipients between October 2008 and December 2011. Anti‐HLA antibodies were measured before and 4–8 weeks after influenza vaccination using a solid‐phase assay. Overall, 169 SOT recipients were included (kidney = 136, lung = 26, liver = 3, and combined = 4). Five (2.9%) of 169 patients developed de novo anti‐HLA antibodies after vaccination, including one patient who developed donor‐specific antibodies (DSA) 8 months after vaccination. In patients with pre‐existing anti‐HLA antibodies, median MFI was not significantly different before and after vaccination (P = 0.73 for class I and P = 0.20 for class II anti‐HLA antibodies) and no development of de novo DSA was observed. Five episodes of rejection (2.9%) were observed within 12 months after vaccination, and only one patient had de novo anti‐HLA antibodies. The incidence of development of anti‐HLA antibodies after influenza vaccination in our cohort of SOT recipients was very low. Our findings indicate that influenza vaccination is safe and does not trigger humoral alloimmune responses in SOT recipients.     

Comparison of the Immunogenicity of a Monovalent Influenza A/H1N1 2009 Vaccine Between Healthy Individuals,Patients With Chronic Renal Failure,and Immunocompromised Populations

Background

Data on the immunogenicity (IG) of the influenza vaccine among patients at high risk of influenza-related complication are limited.

Methods

We studied the antibody titer following a single dose of monovalent 2009 influenza A (H1N1) vaccine between groups of adult patients who were healthy, those with chronic renal failure (CRF), kidney transplant (KT) recipients, and human immunodeficiency virus (HIV)-infected patients. The IG (primary endpoints) was accessed at 4 weeks after vaccination. The secondary endpoint was safety of the vaccine.

Results

A total of 293 patients were studied. Patients' mean age was 41(standard deviation [SD], 13.3) years old. At baseline, mean age (P < .001), history of vaccination in a prior year (P < .001), and geometric mean titers (GMT; P < .001) significantly differed between each groups and the majority (70%) of participants had the hemagglutination inhibition titer <1:10. The IG of the vaccine was highest in the healthy group (71.4 %). The response rate among CRF, KT, and HIV groups was 42.4% (risk ratios [RR], 0.72; 95% confidence interval [CI], 0.5–1.02), 31.9% (RR, 0.51; 95% CI, 0.34–0.76), and 29.7% (RR, 0.42; 95% CI, 0.3–0.6), respectively. The vaccine was well-tolerated in all studied groups. Thirty (10.2%) patients experienced at least 1 adverse reaction but systemic reaction was uncommon (3.4%).

Conclusions

A single dose of monovalent 2009 influenza A (H1N1) vaccine result in poor IG among high-risk populations, including CRF, KT and HIV patients.     

Factors Associated With H1N1 Influenza Vaccine Receipt in a High-Risk Population During the 2009-2010 H1N1 Influenza Pandemic

Background:

Persons with spinal cord injuries and disorders (SCI/D) are at high risk for respiratory complications from influenza. During pandemic situations, where resources may be scarce, uncertainties may arise in veterans with SCI/D.

Objective:

To describe concerns, knowledge, and perceptions of information received during the 2009-2010 H1N1 influenza pandemic and to examine variables associated with H1N1 vaccine receipt.

Methods:

In August 2010, a cross-sectional survey was mailed to a national sample of veterans with traumatic and nontraumatic SCI/D.

Results:

During the pandemic, 58% of veterans with SCI/D received the H1N1 vaccine. Less than two-thirds of non-H1N1 vaccine recipients indicated intentions to get the next season’s influenza vaccine. Being ≥50 years of age and depressed were significantly associated with higher odds of H1N1 vaccination. Being worried about vaccine side effects was associated with lower odds of H1N1 receipt. Compared to individuals who reported receiving an adequate amount of information about the pandemic, those who received too little information had significantly lower odds of receiving the H1N1 vaccine. Those who received accurate/clear information (vs confusing/conflicting) had 2 times greater odds of H1N1 vaccine receipt.

Conclusions:

H1N1 influenza vaccination was low in veterans with SCI/D. Of H1N1 vaccine nonrecipients, only 63% intend to get a seasonal vaccine next season. Providing an adequate amount of accurate and clear information is vital during uncertain times, as was demonstrated by the positive associations with H1N1 vaccination. Information-sharing efforts are needed, so that carry-over effects from the pandemic do not avert future healthy infection prevention behaviors.     

Alternative strategies of posttransplant influenza vaccination in adult solid organ transplant recipients

Solid organ transplant (SOT) recipients are at increased risk of influenza disease and associated complications. The mainstay of prevention is the annual standard-dose influenza vaccine, as studies showed decreased influenza-related morbidity and mortality in vaccinated SOT recipients compared to those unvaccinated. Nonetheless, the immune response in this high-risk population is suboptimal compared to healthy individuals. Over the past two decades, several vaccination strategies have been investigated to overcome this inadequate immune response in SOT recipients. Howbeit, the best vaccination strategy and optimal timing of influenza vaccination remain unclear. This review will provide a detailed summary of studies of various influenza vaccination strategies in adult SOT recipients, discussing immunogenicity results, and addressing their limitations and knowledge gaps.     

Influenza virus vaccination in kidney transplant recipients: serum antibody response to different immunosuppressive drugs

Salles MJC, Sens YAS, Boas LSV, Machado CM. Influenza virus vaccination in kidney transplant recipients: serum antibody response to different immunosuppressive drugs.
Clin Transplant 2010: 24: E17–E23. © 2009 John Wiley & Sons A/S.   Abstract: 
Introduction:  This study prospectively accessed the immune response to the inactivated influenza vaccine in renal transplant recipients receiving either azathioprine or mycophenolate mofetil (MMF). Side effects were investigated.
Methods:  Sixty-nine patients received one dose of inactivated trivalent influenza vaccine. Antihemagglutinin (HI) antibody response against each strain was measured before and one to six months after vaccination.
Results:  Geometric mean HI antibody titers for H1N1 and H3N2 strains increased from 2.57 and 2.44 to 13.45 (p = 0.001) and 7.20 (p < 0.001), respectively. Pre- and post-vaccination protection rates for H1N1 and H3N2 increased from 8.7% to 49.3% (p < 0.001); and 36.3% (p < 0.001) and seroconversion rates were 36% and 25.3%, respectively. There was no response to influenza B. The use of MMF reduced the H1N1 and H3N2 protection rates and the seroconversion rate for the H1N1 strain when compared with the use of azathioprine, and subjects transplanted less than 87 months also had inferior antibody response. Adverse events were mild and there were no change on renal function post-vaccination.
Conclusion:  Renal transplant patients vaccinated against influenza responded with antibody production for influenza A virus strains, but not for influenza B. Use of MMF and shorter time from transplantation decreased the immune response to the vaccine.     

Influenza vaccine antibody responses in lung transplant recipients

CONTEXT: Lung transplant recipients are at high risk of morbidity and mortality from influenza infection because of altered lung physiology and immunosuppression. Annual influenza immunization is recommended, but the ability to mount an antibody response may be limited by immunosuppressant medications. OBJECTIVE: To compare the antibody response rate to influenza vaccine in lung transplant recipients to healthy controls. DESIGN: Open label study. SETTING: Lung transplant clinic and General Clinical Research Center at a university hospital. SUBJECTS: Sixty-eight single and bilateral lung transplant recipients and 35 healthy controls were enrolled in October and November 2002. METHODS: Each individual underwent blood sampling before receiving the 2002-2003 influenza vaccine and 4 weeks later. Influenza antibody concentrations were measured by hemagglutination inhibition assay. Vaccine response rates (antibody concentration >40 hemagglutination units and at least 4-fold increase in antibody concentration) were compared using chi2. The influence of specific immunosuppressants on vaccine response was compared. RESULTS: The influenza vaccine response rate for lung transplant recipients was 29/68 (43%) and 22/35 (63%) for the healthy individuals (P < .05; chi2). Among the recipients, mycophenolate mofetil was associated with poorer influenza vaccine antibody response (> 40 hemagglutination units) (62% vs 91%; P = .01), whereas sirolimus (91% vs 63%; P = .02) was associated with better influenza antibody response compared to those not taking mycophenolate mofetil or sirolimus, respectively. CONCLUSION: Lung transplant recipients had lower influenza vaccine response rates than healthy individuals. Influenza vaccine antibody response is influenced by concomitant administration of mycophenolate mofetil or sirolimus. Future studies should measure protection from influenza infection conferred by immunization and alternative vaccination strategies.     

Appearance of reassortant European avian‐origin H1 influenza A viruses of swine in Vietnam

Three subtypes—H1N1, H1N2 and H3N2—of influenza A viruses of swine (IAV s‐S) are currently endemic in swine worldwide, but there is considerable genotypic diversity among each subtype and limited geographical distribution. Through IAV s‐S monitoring in Vietnam, two H1N2 influenza A viruses were isolated from healthy pigs in Ba Ria‐Vung Tau Province, Southern Vietnam, on 2 December 2016. BLAST and phylogenetic analyses revealed that their HA and NA genes were derived from those of European avian‐like H1N2 IAV s‐S that contained avian‐origin H1 and human‐like N2 genes, and were particularly closely related to those of IAV s‐S circulating in the Netherlands, Germany or Denmark. In addition, the internal genes of these Vietnamese isolates were derived from human A(H1N1)pdm09 viruses, suggesting that the Vietnamese H1N2 IAV s‐S are reassortants between European H1N2 IAV s‐S and human A(H1N1)pdm09v. The appearance of European avian‐like H1N2 IAV s‐S in Vietnam marks their first transmission outside Europe. Our results and statistical analyses of the number of live pigs imported into Vietnam suggest that the European avian‐like H1N2 IAV s‐S may have been introduced into Vietnam with their hosts through international trade. These findings highlight the importance of quarantining imported pigs to impede the introduction of new IAV s‐S.     

Influenza vaccination in heart transplant recipients.

Seventy-nine heart transplant recipients were vaccinated with a trivalent influenza virus vaccine 1996/97 containing the strains A/Singapore/6/86 (H1N1), A/Wuhan/395/95 (H3N2), and B/Beijing/184/93. The proportions of patients with protective levels of antibody (HI > or = 40) after vaccination ranged from 100% (A/Singapore [H1N1]) to 31.6% (B/Beijing) and their mean fold titer increases were lower than those recorded for vaccination of 109 healthy subjects with the same batch of vaccine. The vaccinations were tolerated well and did not result in serious side effects, such as graft rejections. Our findings indicate that influenza vaccination can induce protective antibody levels in a substantial proportion of heart transplant recipients and lend support to the recommendation to vaccinate such patients annually against influenza.     

Influenza Vaccination Is Efficacious and Safe in Renal Transplant Recipients

Whether influenza vaccination in solid-organ transplant recipients is efficacious remains a controversial issue. Furthermore, theoretical concerns have been raised regarding the safety of vaccination as it might trigger rejection of the allograft. The present prospective trial is aimed at investigating the antibody response and safety of influenza vaccination in renal transplant recipients (RTR).
A total of 165 RTR and 41 healthy volunteers were vaccinated with a standard trivalent inactivated influenza vaccine. Hemagglutination-inhibiting (HI) antibodies were quantified before and 1 month after vaccination. Seroprotection (SP) and seroresponse (SR) were defined as a titer ≥40 and a 4-fold rise in HI titer, respectively. Similar SR rates were observed in both groups. Postvaccination SP rates in RTR amounted to 92.7%, 78.7% and 82.9% for A/H1N1, A/H3N2 and B, respectively. High baseline SP rates, most probably reflecting frequent preimmunizations, explain partly the high postvaccination SP rates. SR rate was independently and inversely associated with baseline SP rate. Mycophenolate mofetil ( MMF ) usage was associated with a 2.6–5-fold lower SR. Nonetheless, these patients showed good postvaccination SP rates. A booster dose did not enhance SP or SR rates. Influenza vaccination neither affected allograft function nor caused rejection episodes. In conclusion, influenza vaccination is efficacious and safe in renal transplantation.