Assessment of the immune response to trivalent split influenza vaccine in children with solid tumors

Lessons learnt from influenza vaccination in immunocompromised children undergoing treatment for cancer

Influenza infection contributes substantially to global morbidity and mortality, with children undergoing treatment for cancer among the most vulnerable due to immunosuppression associated with disease and treatment. However, influenza remains one of the most common vaccine-preventable diseases. Despite international guidelines recommending inactivated influenza vaccination on the basis of data supporting efficacy and an excellent safety profile in this population, uptake has often been suboptimal due to persisting hesitancy among both patients and oncologists regarding the ability of the vaccine to mount a sufficient immune response, the optimal vaccine schedule and timing, and the best method to assess response in immunocompromised populations. In this Review, we discuss the evidence regarding influenza vaccination in children with cancer, factors that influence response, and highlight strategies to optimise vaccination. Host immune factors play a substantial role, thus principles learnt from influenza vaccination can be broadly applied for the use of inactivated vaccines in children with cancer.

Influenza Vaccination: Effectiveness, Indications, and Limits in the Pediatric Population

Influenza vaccine is considered the most effective way to prevent influenza. Nonetheless, every year vaccine coverage is lower than recommended in the pediatric population. Many factors are supposed to contribute to this phenomenon such as the uncertainty about the indication for vaccination, and the suboptimal vaccine-effectiveness in pediatric age, especially in the youngest children. In this review we discuss the effectiveness, indications, and limits of influenza vaccination in the pediatric population based on the most recent evidences.

Immune response to influenza vaccination in children with cancer

The aim of this study was to evaluate the ability of influenza immunization to evoke a protective immune response among children with cancer. We evaluated 75 children with cancer who received influenza vaccination. Hemagglutination Inhibition Antibody titers were determined before and after vaccination. The protective rates after vaccination were 79% for H1N1, 75% for H3N2 and 59% for influenza B virus whereas the seroconversion rates were 54%, 44% and 43% respectively. The differences pre- and post-vaccination were significant regardless the method which was used: seroprotection changes, seroconversion and geometric mean titers analyses. Variables such as the pre-vaccination antibody titers, the time when the responses were measured after the vaccination, the age and the type of malignancy as well as the absolute lymphocyte count were found to be correlated with the immune response but the findings were different for each vaccine subunit. In conclusion, influenza vaccination provides protection in a remarkable proportion of pediatric cancer patients whereas this protection is more obvious against H1N1 and H3N2 compared to influenza B. The immune response after vaccination is significant and seems to be influenced by a variety of factors.

Vaccination in immunocompromised host: Recommendations of Italian Primary Immunodeficiency Network Centers (IPINET)

Infectious complications are a major cause of morbidity and mortality in patients with primary or secondary immunodeficiency. Prevention of infectious diseases by vaccines is among the most effective healthcare measures mainly for these subjects. However immunocompromised people vary in their degree of immunosuppression and susceptibility to infection and, therefore, represent a heterogeneous population with regard to immunization. To date there is no well- established evidence for use of vaccines in immunodeficient patients, and indications are not clearly defined even in high-quality reviews and in most of the guidelines prepared to provide recommendations for the active vaccination of immunocompromised hosts. The aim of this document is to issue recommendations based on published literature and the collective experience of the Italian primary immunodeficiency centers, about how and when vaccines can be used in immunocompromised patients, in order to facilitate physician decisions and to ensure the best immune protection with the lowest risk to the health of the patient.

Serologic response and clinical efficacy of influenza vaccination in children and young adults on chemotherapy for cancer

BACKGROUND

Influenza is a health risk to children receiving chemotherapy for cancer. An absolute lymphocyte count (ALC) >1,000 cells/mm(3) has been associated with the ability to produce an immune response to influenza vaccine during chemotherapy. However, clinical efficacy of influenza vaccination during chemotherapy remains unclear.

PROCEDURE

We conducted a prospective cohort study in children receiving chemotherapy for cancer during two consecutive influenza seasons. Assessments of immune cells and serologic response were measured immediately before and after receiving influenza vaccine. Patients were monitored for influenza or influenza-like illness (ILI).

RESULTS

Two hundred fifty-nine patients were studied over 2 years. The seroresponse rate was 62% (98/157). The median ALC at vaccination was higher in seroresponders than nonresponders, 854 cells/mm(3) versus 602 cells/mm(3) , respectively (P < 0.036). Univariate analysis showed that patients with an ALC <1,000 cells/mm(3) at the time of vaccination were twice as likely to be sero-nonresponders (P < 0.02, OR = 2.4, 95% CI: 1.1-5.0). Twelve percent (31/259) of patients developed influenza, of whom all had fever at presentation, 26% (8/31) required hospitalization, and 81% (25/31) had chemotherapy delays. No deaths were associated with influenza infection. The proportion of patients with influenza was not different between seroresponders and nonresponders.

CONCLUSIONS

Influenza infection following immunization remains a source of morbidity in children undergoing chemotherapy. Lymphopenia at vaccination predicted sero-nonresponse. Seroresponse was not associated with a decreased frequency of influenza infection or ILI when compared to sero-nonresponders, suggesting clinical effectiveness of vaccination is likely multifactorial. Further investigation into the efficacy of the influenza vaccine is needed to refine immunization recommendations.

Immunogenicity and safety of high-dose trivalent inactivated influenza vaccine compared to standard-dose vaccine in children and young adults with cancer or HIV infection

BACKGROUND

Approaches to improve the immune response of immunocompromised patients to influenza vaccination are needed.

METHODS

Children and young adults (3-21 years) with cancer or HIV infection were randomized to receive 2 doses of high-dose (HD) trivalent influenza vaccine (TIV) or of standard-dose (SD) TIV. Hemagglutination inhibition (HAI) antibody titers were measured against H1, H3, and B antigens after each dose and 9 months later. Seroconversion was defined as ≥4-fold rise in HAI titer comparing pre- and post-vaccine sera. Seroprotection was defined as a post-vaccine HAI titer ≥1:40. Reactogenicity events (RE) were solicited using a structured questionnaire 7 and 14 days after each dose of vaccine, and adverse events by medical record review for 21 days after each dose of vaccine.

RESULTS

Eighty-five participants were enrolled in the study; 27 with leukemia, 17 with solid tumor (ST), and 41 with HIV. Recipients of HD TIV had significantly greater fold increase in HAI titers to B antigen in leukemia group and to H1 antigen in ST group compared to SD TIV recipients. This increase was not documented in HIV group. There were no differences in seroconversion or seroprotection between HD TIV and SD TIV in all groups. There was no difference in the percentage of solicited RE in recipients of HD TIV (54% after dose 1 and 38% after dose 2) compared to SD TIV (40% after dose 1 and 20% after dose 2, p=0.27 and 0.09 after dose 1 and 2, respectively).

CONCLUSION

HD TIV was more immunogenic than SD TIV in children and young adults with leukemia or ST, but not with HIV. HD TIV was safe and well-tolerated in children and young adults with leukemia, ST, or HIV.

Immunogenicity and clinical effectiveness of the trivalent inactivated influenza vaccine in immunocompromised children undergoing treatment for cancer

Influenza is associated with significant morbidity and mortality in children receiving therapy for cancer, yet recommendation for, and uptake of the seasonal vaccine remains poor. One hundred children undergoing treatment for cancer were vaccinated with the trivalent inactivated influenza vaccine according to national guidelines in 2010 and 2011. Influenza‐specific hemagglutinin inhibition antibody titers were performed on blood samples taken prior to each vaccination and 4 weeks following the final vaccination. A nasopharyngeal aspirate for influenza was performed on all children who developed an influenza‐like illness. Following vaccination, seroprotection and seroconversion rates were 55 and 43% for H3N2, 61 and 43% for H1N1, and 41 and 33% for B strain, respectively. Overall, there was a significant geometric mean fold increase to H3N2 (GMFI 4.56, 95% CI 3.19–6.52, P < 0.01) and H1N1 (GMFI 4.44, 95% CI 3.19–6.19, P < 0.01) strains. Seroconversion was significantly more likely in children with solid compared with hematological malignancies and in children <10 years of age who received a two‐dose schedule compared to one. Influenza infection occurred in 2% of the vaccinated study population, compared with 6.8% in unvaccinated controls, providing an adjusted estimated vaccine effectiveness of 72% (95% CI −26–94%). There were no serious adverse events and a low reactogenicity rate of 3%. The trivalent inactivated influenza vaccine is safe, immunogenic, provides clinical protection and should be administered annually to immunosuppressed children receiving treatment for cancer. All children <10 years of age should receive a two‐dose schedule.

Quality improvement initiative to increase influenza vaccination in pediatric cancer patients

BACKGROUND

Pediatric patients with cancer face more severe complications of influenza than healthy children. Although Centers for Disease Control and Prevention guidelines recommend yearly vaccination in these patients, in our large academic center, <60% of oncology patients receiving chemotherapy were immunized at baseline. Our objective was to increase this rate through a multifaceted quality improvement initiative.

METHODS

Eligible patients were >6 months old, within 1 year of receiving chemotherapy, >100 days from stem cell transplant, and had ≥ 1 outpatient oncology visit between September 1, 2012, and March 31, 2013. Five interventions were instituted concomitantly: (1) family education: influenza/vaccine handouts were provided to families in clinic waiting rooms; (2) health informatics: daily lists of outpatients due for immunization were generated from the electronic medical record and sent automatically to triage staff and nurses; (3) outpatient clinic: patients due for vaccination were given colored wristbands during triage to alert providers; (4) inpatient: vaccine order was built into admission order set; and (5) provider education: staff education was provided at conferences on screening of patients, vaccine ordering, and documentation of refusals/contraindications.

RESULTS

The complete influenza immunization rate increased by 20.1% to 64.5%, and the proportion of patients receiving ≥ 1 dose of vaccination increased by 22.9% to 77.7%. Similar changes were noted across all cancer types, with highest rates of immunization in leukemia/lymphoma patients (86.8%) and lowest in patients after stem cell transplant (66.7%).

CONCLUSIONS

Technology, education, and multidisciplinary clinical process changes increased influenza vaccination rates. Ongoing efforts are targeting subgroups with lowest rates of immunization.

Guidelines on vaccinations in paediatric haematology and oncology patients

OBJECTIVE

Vaccinations are the most important tool to prevent infectious diseases. Chemotherapy-induced immune depression may impact the efficacy of vaccinations in children.

PATIENTS AND METHODS

A panel of experts of the supportive care working group of the Italian Association Paediatric Haematology Oncology (AIEOP) addressed this issue by guidelines on vaccinations in paediatric cancer patients. The literature published between 1980 and 2013 was reviewed.

RESULTS AND CONCLUSION

During intensive chemotherapy, vaccination turned out to be effective for hepatitis A and B, whilst vaccinations with toxoid, protein subunits, or bacterial antigens should be postponed to the less intensive phases, to achieve an adequate immune response. Apart from varicella, the administration of live-attenuated-virus vaccines is not recommended during this phase. Family members should remain on recommended vaccination schedules, including toxoid, inactivated vaccine (also poliomyelitis), and live-attenuated vaccines (varicella, measles, mumps, and rubella). By the time of completion of chemotherapy, insufficient serum antibody levels for vaccine-preventable diseases have been reported, while immunological memory appears to be preserved. Once immunological recovery is completed, usually after 6 months, response to booster or vaccination is generally good and allows patients to be protected and also to contribute to herd immunity.

Influenza vaccination in children being treated with chemotherapy for cancer

BACKGROUND

Influenza infection is a potential cause of severe morbidity in children with cancer; therefore vaccination against influenza is recommended. However, data are conflicting regarding the immune response to influenza vaccination in children with cancer, and the value of vaccination remains unclear.

OBJECTIVES

1. To assess the efficacy of influenza vaccination in stimulating an immunological response in children with cancer during chemotherapy, compared with control groups.2. To assess the efficacy of influenza vaccination in preventing confirmed influenza and influenza-like illness and/or in stimulating immunological response in children with cancer treated with chemotherapy, compared with placebo, no intervention or different dosage schedules.3. To identify the adverse effects associated with influenza vaccines in children with cancer treated with chemotherapy, compared with other control groups.

SEARCH METHODS

We searched the Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE (1966 to 2012) and EMBASE (1980 to 2012) up to August 2012. We also searched reference lists of relevant articles and conference proceedings of the Interscience Conference on Antimicrobial Agents and Chemotherapy (ICAAC), the Infectious Diseases Society of America (IDSA), the Multinational Association of Supportive Care in Cancer (MASCC) and the International Society of Paediatric Oncology (SIOP).

SELECTION CRITERIA

We considered randomised controlled trials (RCTs) and controlled clinical trials (CCTs) in which the serological response to influenza vaccination of children with cancer was compared with that of control groups. We also considered RCTs and CCTs that compared the effects of influenza vaccination on clinical response and/or immunological response in children with cancer being treated with chemotherapy, compared with placebo, no intervention or different dosage schedules.

DATA COLLECTION AND ANALYSIS

Two independent review authors assessed the methodological quality of included studies and extracted the data.

MAIN RESULTS

We included 1 RCT and 9 CCTs (total number of participants = 770). None of the included studies reported clinical outcomes. All included studies reported on influenza immunity and adverse reactions to vaccination. In five studies, immune responses to influenza vaccine were compared in 272 children receiving chemotherapy and 166 children not receiving chemotherapy. In four studies, responses to influenza vaccine were assessed in 236 children receiving chemotherapy compared with responses in 142 healthy children. Measures used to assess immune responses included a four-fold rise in antibody titre after vaccination, development of a haemagglutination inhibition (HI) titre > 32 and pre- and post-vaccination geometric mean titres (GMTs). Immune responses in children receiving chemotherapy were consistently weaker (four-fold rise of 38% to 65%) than those in children who had completed chemotherapy (50% to 86%) and in healthy children (53% to 89%). In terms of adverse effects, 391 paediatric oncology patients received influenza vaccine, and the adverse effects described included mild local reactions and low-grade fever. No life-threatening or persistent adverse effects were reported.

AUTHORS' CONCLUSIONS

Paediatric oncology patients receiving chemotherapy are able to generate an immune response to the influenza vaccine, but it remains unclear whether this immune response protects them from influenza infection or its complications. We are awaiting results from well-designed RCTs addressing the clinical benefit of influenza vaccination in these patients.

Protecting pediatric oncology patients from influenza

Influenza is a common respiratory pathogen. Its severity can be unpredictable, but people with chronic illness are at increased risk of severe infection, complications, and death from influenza. This review examines evidence to support various strategies to protect pediatric oncology patients from influenza-related morbidity. Influenza vaccination should be considered standard. Additional evidence-supported measures include antiviral treatment, antiviral prophylaxis, cohorting of patients, and hospital infection control measures. Data from other high-risk populations support the vaccination of family members, double-dose or high-dose vaccination, and the use of barrier methods. These measures have the potential to optimize patient outcomes because there will be fewer treatment interruptions for acute illness. These strategies can also protect patients from prolonged hospitalizations and morbidity related to influenza.

Successful H1N1 influenza vaccination of children receiving chemotherapy for solid tumors

BACKGROUND

The hemato-oncology community has been seriously concerned about the H1N1 pandemic of 2009. Here, we report on the evaluation of the immunogenicity and tolerability of H1N1v monovalent vaccines in young patients with cancer during this pandemic.

PROCEDURE

Between December 7, 2009 and February 26, 2010, 20 children receiving chemotherapy for solid tumors at the Institute of Hematology and Pediatric Oncology of Lyon, were immunized by 2 doses of either AS03-adjuvanted or nonadjuvanted vaccine. The level of specific antibodies was assessed at D21 and D42.

RESULTS

Seroconversion was observed in 13 of the 20 cases (65%), and 18 of 20 cases (90%) had protective titers after the 2 doses. Exploratory univariate analysis failed to show a significant influence of prevaccination lymphocyte counts on seroresponse rates.

CONCLUSIONS

These data suggest that H1N1v monovalent vaccines were well tolerated by young cancer patients while on chemotherapy and achieved protective immune response in most cases.

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.

Immune response to 2009 pandemic H1N1 influenza virus A monovalent vaccine in children with cancer

PURPOSE

This study investigated the immune response to 2009 pandemic H1N1 influenza monovalent vaccine in children with cancer receiving chemotherapy.

METHODS

We enrolled 25 pediatric patients. Ten patients younger than 10 years old received two vaccinations and the remaining 15 patients older than 10 years old received one. We checked hemagglutination-inhibition (HAI) antibody titers in sera of patients before and 3-4 weeks after vaccination. Seroprotective titer was defined as HAI antibody titer ≥ 40 and seroresponse as ≥ 4-fold increase in HAI antibody titers after vaccination.

RESULTS

The pre- and post-vaccination seroprotective rates were 52% and 72% (P = 0.24). Sixteen (64%) patients were possibly exposed to 2009 pandemic H1N1 influenza previously, and there was significant association between possible exposure and pre-vaccination seroprotective rate (P = 0.03). Post-vaccination seroresponse rate was 32%, and seroresponse was greater in patients without pre-vaccination seroprotective titer than those with pre-vaccination seroprotective titer (50% vs. 15%, P = 0.07). Children with lymphocyte counts above 1,500/µl during vaccination period had better seroresponse than those with lymphocyte counts below 1,500/µl (P = 0.008). Post-vaccination geometric mean titer (GMT) significantly increased in patients younger than 10 years receiving two vaccinations (pre- and post-vaccination GMT were 21.4 and 60.6, respectively; P = 0.025).

CONCLUSIONS

Monovalent vaccine for the 2009 pandemic H1N1 influenza A was found to be partially immunogenic in children with cancer, as evidenced by 32% of seroresponse rate. Immune response can be improved with vaccinations administered to patients whose absolute lymphocyte counts returned to a level of 1,500/µl or higher.

The efficacy of influenza vaccination in a pediatric oncology population

There is little known about the impact of the timing of influenza vaccine administration on seroconversion in patients on chemotherapy. Recommendations for other vaccines state that the vaccines should be readministered several months after the completion of chemotherapy outside of the stem cell transplant setting. This is not often possible with the influenza vaccine because of its seasonal nature. To examine whether certain times during chemotherapy are more favorable for seroconversion, we examined vaccine responses in a cohort of children on chemotherapy. Pediatric patients on chemotherapy were recruited over the 2006 to 2008 influenza vaccine seasons. Sixty-eight acute lymphoblastic leukemia (ALL), 3 acute myeloid leukemia, and 18 sarcoma patients were evaluated. Clinical and laboratory features were recorded. The hemagglutination inhibition (HAI) assay was used to define serotype-specific responses. Seroconversion rates varied according to the type of chemotherapy during the vaccination period. In some cases, there was a late rise in titer, suggesting that a wild-type infection had occurred, leading to an estimate of vulnerability of this population. In patients with ALL, responses to the vaccine were greater when it was given early in the course of treatment. We conclude that seroconversion rates are well below the rates cited for the general population. The 3 acute myeloid leukemia patients had a particularly poor response to the vaccine. In the case of ALL patients, it may be possible to adjust the timing of the vaccine to optimize the response.

Utility of Influenza Vaccination for Oncology Patients

Every fall and winter, patients with cancer and their families ask oncologists whether they should be vaccinated for influenza. This season, with escalating concerns regarding the novel H1N1 influenza virus and its recently approved vaccine, this question has become more frequent and increasingly urgent. The purpose of this article is to review evidence related to the ability of patients with cancer to mount protective immunological responses to influenza vaccination. The literature on immunogenicity in pediatric and adult patients, those with solid tumors and hematologic malignancies, untreated and actively treated patients, and patients receiving biologic agents is summarized and reviewed. In addition, we report on potential strategies to improve the efficacy of influenza vaccination in patients with cancer, such as the timing of vaccination, use of more than a one-shot series, increasing the antigen dose, and the use of adjuvant therapies. We conclude that there is evidence that patients with cancer receiving chemotherapy are able to respond to influenza vaccination, and because this intervention is safe, inexpensive, and widely available, vaccination for seasonal influenza and the novel H1N1 strain is indicated.

Immunogenicity of trivalent influenza vaccine in children with acute lymphoblastic leukemia during maintenance therapy

PURPOSE

The aim of this study was to assess the immune response of children with acute lymphoblastic leukemia (ALL) to influenza vaccine and to compare it with healthy controls.

PROCEDURE

Thirty-two children aged 1-18 years with ALL on maintenance therapy and 30 healthy sibling controls were enrolled in the study. All children were vaccinated with trivalent inactivated influenza vaccine. Hemagglutinin-inhibition (HI) antibody titers were determined in sera of both patient and control groups just before and 4 weeks after vaccination. The ability of each group to mount a protective (> or =40) and/or fourfold titer was measured.

RESULTS

The protective response for virus subunits among patients and healthy controls were 43.4% versus 88% for H1N1 (P = 0.04), 63.3% versus 80% for H3N2 antigens (P = 0.06), and 26% versus 73% for B antigen (P = 0.001). Responses for H1N1 and B subunits were significantly lower in patients than controls. In the patient group, the significant response to each virus was demonstrated in the analysis of pre- and post-vaccination geometric mean titer (GMT) (P = 0.001). The percentage of patients and controls with fourfold increase in HI titers were 56.2% versus 80% for H1N1 (P = 0.04), 40.6% versus 53.3% for H3N2 (P = 0.31), and 59.4% versus 83.3% for B (P = 0.038). Immune responses for H1N1 and B subunits were significantly lower in patients than controls.

CONCLUSIONS

Influenza vaccine is tolerated well in ALL patients with acceptable but limited immune response compared to healthy controls. These findings support the recommendation for annual influenza vaccination in children with ALL.

Impact of influenza-like illness and effectiveness of influenza vaccination in oncohematological children who have completed cancer therapy

In order to evaluate the impact of influenza-like illness and the effectiveness of influenza vaccination in children with oncohematological disease who have completed cancer therapy, 182 children with a diagnosis of oncohematological disease were divided into two subgroups on the basis of the length of time off therapy (<6 months or 6-24 months) and randomised 1:1 to receive influenza vaccination or not. The controls were 91 otherwise healthy children unvaccinated against influenza. The results show that the clinical and socioeconomic impact of influenza-like illnesses and the effectiveness of influenza vaccination in oncohematological children who have completed cancer therapy are related to the length of the off therapy period, and seem to be significantly greater in those who have been off therapy for less than 6 months in comparison with healthy controls. This suggests that the administration of influenza vaccination should be strongly recommended only among oncohematological children who have been off therapy for less than 6 months.