Evaluation of Vaccine Immunogenicity-Correlates to Real-World Protection: Influenza

Recent events highlighted that, despite decades of studying vaccine immunogenicity and efforts toward finding correlates of protection, evaluating real-world vaccine efficacy as well as establishing meaningful licensing criteria still represents a significant challenge. In this paper, we review all aspects of influenza vaccine immunogenicity, including animal and human challenge studies, humoral and cellular immunity parameters, and their potential correlation with real-life protection from disease.

Reducedhumoral response against variants of concern in childhood solid cancer patients compared to adult patients and healthy children after SARS-CoV-2 vaccination

Introduction

Although there is extended research on the response to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) vaccines in adult cancer patients (ACP), the immunogenicity to the variants of concern (VOCs) in childhood cancer patients (CCP) and safety profiles are now little known.

Methods

A prospective, multi-center cohort study was performed by recruiting children with a solid cancer diagnosis and childhood healthy control (CHC) to receive standard two-dose SARS-CoV-2 vaccines. An independent ACP group was included to match CCP in treatment history. Humoral response to six variants was performed and adverse events were followed up 3 months after vaccination. Responses to variants were compared with ACP and CHC by means of propensity score-matched (PSM) analysis.

Results

The analysis included 111 CCP (27.2%, median age of 8, quartile 5.5-15 years), 134 CHC (32.8%), and 163 ACP (40.0%), for a total 408 patients. Pathology included carcinoma, neural tumors, sarcoma, and germ cell tumors. Median chemotherapy time was 7 (quartile, 5-11) months. In PSM sample pairs, the humoral response of CCP against variants was significantly decreased, and serology titers (281.8 ± 315.5 U/ml) were reduced, as compared to ACP (p< 0.01 for the rate of neutralization rate against each variant) and CHC (p< 0.01 for the rate of neutralization against each variant) groups. Chemotherapy time and age (Pearson r ≥ 0.8 for all variants) were associated with the humoral response against VOCs of the CHC group. In the CCP group, less than grade II adverse events were observed, including 32 patients with local reactions, and 29 patients had systemic adverse events, including fever (n = 9), rash (n = 20), headache (n = 3), fatigue (n = 11), and myalgia (n = 15). All reactions were well-managed medically.

Conclusions

The humoral response against VOCs after the CoronaVac vaccination in CCP was moderately impaired although the vaccine was safe. Age and chemotherapy time seem to be the primary reason for poor response and low serology levels.

Therapeutic Vaccination in Head and Neck Squamous Cell Carcinoma—A Review

Therapeutic vaccination is one of the most effective immunotherapeutic approaches, second only to immune checkpoint inhibitors (ICIs), which have already been approved for clinical use. Head and neck squamous cell carcinomas (HNSCCs) are heterogenous epithelial tumors of the upper aerodigestive tract, and a significant proportion of these tumors tend to exhibit unfavorable therapeutic responses to the existing treatment options. Comprehending the immunopathology of these tumors and choosing an appropriate immunotherapeutic maneuver seems to be a promising avenue for solving this problem. The current review provides a detailed overview of the strategies, targets, and candidates for therapeutic vaccination in HNSCC. The classical principle of inducing a potent, antigen-specific, cell-mediated cytotoxicity targeting a specific tumor antigen seems to be the most effective mechanism of therapeutic vaccination, particularly against the human papilloma virus positive subset of HNSCC. However, approaches such as countering the immunosuppressive tumor microenvironment of HNSCC and immune co-stimulatory mechanisms have also been explored recently, with encouraging results.

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.

Safety and Efficacy of Spray Intranasal Live Attenuated Influenza Vaccine: Systematic Review and Meta-Analysis

Although influenza is a major public health concern, little is known about the use of spray live attenuated influenza vaccine (LAIV) among adults. For this reason, we conducted a systematic review and meta-analysis to investigate the efficacy and safety of LAIV, especially in adults with/without clinical conditions and children <2 years, with the final aim of possibly extending the clinical indications. PubMed/MEDLINE and Scopus were the two databases consulted through February 2021. The Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines were followed. A critical appraisal was conducted. Analyses were performed by using ProMeta3 software. Twenty-two studies were included, showing that LAIV was associated with a higher probability of seroconversion when compared with a placebo and considering the A/H1N1 serotype (pooled OR = 2.26 (95% CI = 1.12–4.54), p-value = 0.022; based on 488 participants, without heterogeneity (I2 = 0.0%)). The meta-analysis also confirmed no significant association with systemic adverse events. Only rhinorrhea, nasal congestion, and sore throat were significantly associated with LAIV compared to the placebo. Despite limited available evidence, LAIV has proved to be a safe and effective flu vaccination, also due to its very low invasiveness, and our review’s results can be considered a starting point for guiding future research and shaping forthcoming vaccination campaigns.

Factors influencing the immunogenicity of influenza vaccines

Annual vaccination is the best prevention of influenza. However, the immunogenicity of influenza vaccines varies among different populations. It is important to fully identify the factors that may affect the immunogenicity of the vaccines to provide best protection for vaccine recipients. This paper reviews the factors that may influence the immunogenicity of influenza vaccines from the aspects of vaccine factors, adjuvants, individual factors, repeated vaccination, and genetic factors. The confirmed or hypothesized molecular mechanisms of these factors have also been briefly summarized.

Covid-19 Vaccination Options for Immunosuppressed Cancer Patients

Background: Currently, many COVID-19 vaccine candidates are being developed to end the pandemic; however, immunosuppressed cancer patients have been excluded from the participating criteria. It is important that they are able to examine their options for achieving immunity against COVID-19. Purpose: This review aims to discuss the available options that can be taken to vaccinate immunosuppressed cancer patients when no vaccine is being developed for their safety. Method: A literature study was conducted using Google Scholar, DOAJ, and GARUDA Library on November 2, 2020, focusing on articles examining vaccination guidelines for immunosuppressed cancer patients. Results: The search found 200 articles, which were curated to obtain 13 articles that satisfied all inclusion criteria. These consist of four guidelines, five reviews, and four research articles. Based on the literature, immunosuppressed cancer patients have the option to use the vaccines currently under development, with precautions set for live attenuated and potentially infectious vaccines. Vaccination timing also needs to be adjusted so as to fall at a certain time before or after the immunosuppressive condition. Moreover, a more complete COVID-19 immunity can be achieved through a synergy between individual vaccination and the construction of herd immunity. Conclusion: Most of the vaccines currently under development may be safe for cancer patients, being mindful of several considerations. Here, herd immunity can serve as a complement to individual immunity.

Respiratory Viral Infections in Patients With Cancer or Undergoing Hematopoietic Cell Transplant

Survival rates for pediatric cancer have steadily improved over time but it remains a significant cause of morbidity and mortality among children. Infections are a major complication of cancer and its treatment. Community acquired respiratory viral infections (CRV) in these patients increase morbidity, mortality and can lead to delay in chemotherapy. These are the result of infections with a heterogeneous group of viruses including RNA viruses, such as respiratory syncytial virus (RSV), influenza virus (IV), parainfluenza virus (PIV), metapneumovirus (HMPV), rhinovirus (RhV), and coronavirus (CoV). These infections maintain a similar seasonal pattern to those of immunocompetent patients. Clinical manifestations vary significantly depending on the type of virus and the type and degree of immunosuppression, ranging from asymptomatic or mild disease to rapidly progressive fatal pneumonia Infections in this population are characterized by a high rate of progression from upper to lower respiratory tract infection and prolonged viral shedding. Use of corticosteroids and immunosuppressive therapy are risk factors for severe disease. The clinical course is often difficult to predict, and clinical signs are unreliable. Accurate prognostic viral and immune markers, which have become part of the standard of care for systemic viral infections, are currently lacking; and management of CRV infections remains controversial. Defining effective prophylactic and therapeutic strategies is challenging, especially considering, the spectrum of immunocompromised patients, the variety of respiratory viruses, and the presence of other opportunistic infections and medical problems. Prevention remains one of the most important strategies against these viruses. Early diagnosis, supportive care and antivirals at an early stage, when available and indicated, have proven beneficial. However, with the exception of neuraminidase inhibitors for influenza infection, there are no accepted treatments. In high-risk patients, pre-emptive treatment with antivirals for upper respiratory tract infection (URTI) to decrease progression to LRTI is a common strategy. In the future, viral load and immune markers may prove beneficial in predicting severe disease, supporting decision making and monitor treatment in this population.

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.

Influenza vaccines: Evaluation of the safety profile

The safety of vaccines is a critical factor in maintaining public trust in national vaccination programs. Vaccines are recommended for children, adults and elderly subjects and have to meet higher safety standards, since they are administered to healthy subjects, mainly healthy children. Although vaccines are strictly monitored before authorization, the possibility of adverse events and/or rare adverse events cannot be totally eliminated. Two main types of influenza vaccines are currently available: parenteral inactivated influenza vaccines and intranasal live attenuated vaccines. Both display a good safety profile in adults and children. However, they can cause adverse events and/or rare adverse events, some of which are more prevalent in children, while others with a higher prevalence in adults. The aim of this review is to provide an overview of influenza vaccine safety according to target groups, vaccine types and production methods.

Immunizations in solid organ and hematopoeitic stem cell transplant patients: A comprehensive review

The Solid Organ Transplantation (SOT) and Haematopoietic Stem Cell Transplantation (HSCT) population is continuously increasing as a result of broader indications for transplant and improved survival. Infectious diseases, including vaccine-preventable diseases, are a significant threat for this population, primarily after but also prior to transplantation. As a consequence, clinicians must ensure that patients are optimally immunized before transplantation, to provide the best protection during the early post-transplantation period, when immunosuppression is the strongest and vaccine responses are poor. After 3-6 months, inactivated vaccines immunization can be resumed. By contrast, live-attenuated vaccines are lifelong contraindicated in SOT patients, but can be considered in HSCT patients at least 2 years after transplantation, if there is no immunosuppression or graft-versus-host-disease. However, because of the advantages of live-attenuated over inactivated vaccines--and also sometimes the absence of an inactivated alternative--an increasing number of prospective studies on live vaccine immunization after transplantation are performed and give new insights about safety and immunogenicity in this population.

The safety of influenza vaccines in children: An Institute for Vaccine Safety white paper

Most influenza vaccines are generally safe, but influenza vaccines can cause rare serious adverse events. Some adverse events, such as fever and febrile seizures, are more common in children than adults. There can be differences in the safety of vaccines in different populations due to underlying differences in genetic predisposition to the adverse event. Live attenuated vaccines have not been studied adequately in children under 2 years of age to determine the risks of adverse events; more studies are needed to address this and several other priority safety issues with all influenza vaccines in children. All vaccines intended for use in children require safety testing in the target age group, especially in young children. Safety of one influenza vaccine in children should not be extrapolated to assumed safety of all influenza vaccines in children. The low rates of adverse events from influenza vaccines should not be a deterrent to the use of influenza vaccines because of the overwhelming evidence of the burden of disease due to influenza in children.

Improving influenza vaccination in chronically ill children using a tertiary-care based vaccination clinic: Is there a role for the live-attenuated influenza vaccine (LAIV)?

BACKGROUND

Children with underlying medical conditions should receive influenza vaccine (IV) yearly; yet this remains sub-optimal. We aimed to describe our experience with a tertiary-care hospital-based influenza vaccination clinic for this at-risk population.

METHODS

From October to December 2012, 2013, and 2014, we ran an influenza vaccination clinic at the Montreal Children's Hospital, where children with high-risk conditions come for their follow-up. Both injectable IV (IIV) and live-attenuated IV (LAIV) were offered free of charge to patients and their household contacts. Upon vaccination, parents were asked to fill a pre-piloted questionnaire.

RESULTS

We vaccinated a total of 2640 high-risk children and 1912 household members during the three influenza vaccination seasons. In 2012 and 2013, 631 and 630 patients with chronic illnesses were vaccinated, compared to 1379 in 2014. Caregivers preferred LAIV primarily because no needle was involved (49.0%) and because it was perceived as less painful (46.9%). LAIV was administered to 69% (2012), 55% (2013) and 47% (2014) of high-risk children. The main reason for not receiving LAIV was because it was contra-indicated. A small fraction of children previously vaccinated with LAIV who did not present any contraindication to LAIV opted for IIV: 12/101 (11.8%) in 2013 and 16/272 (5.9%) in 2014. In 2014, this was mainly due to a previous negative experience with LAIV (11/16).

CONCLUSION

Having an influenza vaccination clinic on site at a tertiary care hospital, where children come for their scheduled visits, facilitates yearly influenza vaccination in children with chronic illnesses. LAIV is preferred by caregivers and patients, when not contraindicated.

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.

Comparison of immune response to the influenza vaccine in obese and nonobese healthcare workers

OBJECTIVE

To determine whether there is a difference in antibody titers and functionality after receipt of the influenza vaccine for obese versus nonobese healthcare workers (HCW).

DESIGN

Prospective observational study.

SETTING

Tertiary medical center.

PARTICIPANTS

Healthcare workers. METHODS Baseline influenza antibody titers for obese and nonobese HCW were recorded during the hospital's 2011 annual influenza vaccination day and follow-up antibody titers were measured 4 weeks later. Antibodies were measured using the hemagglutination inhibition assay and functionality was measured using the micro-neutralization method.

RESULTS

Of 200 initial HCWs, 190 completed the study (97 obese and 93 nonobese). Seroprotection after immunization was not significantly different for nonobese compared with obese HCW for each strain (influenza A [H1N1], 99% and 99%; influenza A [H3N2], 100% and 99%; and influenza B, 67% and 71%, respectively) All geometric mean titers measured by micro-neutralization showed statistically significant increases in activity. In comparison, there was no difference in the 4-fold increase in H1N1 or B titers. There was a significant difference in the 4-fold increase of H3N2 titers between the nonobese and obese HCWs (82/93 [88%] vs 64/97 [66%], P=.003) In an ad hoc analysis we found that obese HCWs had a statistically greater number of 4-fold decreases in titers with H1N1 and H3N2.

CONCLUSIONS

There was no significant difference in protection from influenza between obese and nonobese HCWs after immunization.

Safety, immunogenicity and shedding of LAIV4 in HIV-infected and uninfected children

OBJECTIVES

HIV-infected children have poor responses to inactivated influenza vaccines. Live vaccines (LAIVs) are highly efficacious in children, but they are not used in HIV-infected children du e to limited information. We investigated the safety, immunogenicity and viral shedding of LAIV4 in HIV-infected compared with uninfected children.

DESIGN

Forty-six HIV-infected and 56 uninfected children 2 to 25 years old, who had been previously vaccinated against influenza, consented to receive a single dose of LAIV4. All grade adverse events (AEs) were recorded in the first month post-vaccination and serious AEs (SAEs) throughout the influenza season. Nasopharyngeal swabs for influenza PCR and IgA ELISA and blood for hemagglutination inhibition antibody (HAI) measurements were collected at entry, 2-5, 7-10 and 21-28 days post-vaccination.

RESULTS

The HIV-infected subjects had median CD4+ cells of 649 cells/μL and plasma HIV RNA of 20 copies/mL. AEs were similar in the two groups. There were no vaccine-related SAEs. Shedding of ≥1 vaccine virus was detected in 67% HIV-infected and 50% uninfected participants (p=0.14). HAI titers did not appreciably change, but mucosal IgA antibodies significantly increased post-vaccination in both groups. High baseline HAI and IgA antibody concentrations were associated with decreased viral shedding in controls, but not in HIV-infected subjects. Similar proportions of HIV-infected vaccinees and controls reported influenza-like illnesses (12% and 6%) throughout the season.

CONCLUSIONS

LAIV4 was equally safe and immunogenic and caused similar viral shedding in HIV-infected and uninfected children. A correlate of protection against vaccine viral shedding was not identified in HIV-infected participants, although both circulating and mucosal antibodies correlated with protection in controls.

Practical review of immunizations in adult patients with cancer

Compared with the general population, patients with cancer in general are more susceptible to vaccine-preventable infections, either by an increased risk due to the malignancy itself or immunosuppressive treatment. The goal of immunizations in these patients is therefore to provide protection against these infections, and to decrease the number of vulnerable patients who can disseminate these organisms. The proper timing of immunization with cancer treatment is key to achieving better vaccine protection. As the oncology field continues to advance, leading to better quality of life and longer survival, immunization and other aspects of preventive medicine ought to move to the frontline in the care of these patients. Herein, we review the vaccines most clinically relevant to patients with cancer, as well as special cases including vaccines after splenectomy, travel immunization and recommendations for family members.

The Use of Live Attenuated Influenza Vaccine (LAIV) in Healthcare Personnel (HCP): Guidance from the Society for Healthcare Epidemiology of America (SHEA)

Because of the live viral backbone of live attenuated influenza vaccine (LAIV), questions have arisen regarding infection control precautions and restrictions surrounding its use in healthcare personnel (HCP). This document provides guidance from the Society for Healthcare Epidemiology of America regarding use of LAIV in HCP and the infection control precautions that are recommended with its use in this population.

Infect Control Hosp Epidemiol 2012;33(10):981-983

Effects of biological and non-biological immunomodulatory therapies on the immunogenicity of vaccines in patients with rheumatic diseases

Vaccinations are administered to patients to induce a protective immune response, resulting in immunological memory. Preventing infection through the use of vaccines is particularly important in immunocompromised and immunosuppressed individuals given their increased frequency and severity of infections relative to healthy individuals. Recent surveys show that the vaccination rate is still alarmingly low in patients with rheumatic disease. In this review we briefly discuss the different types of vaccines and then critically examine evidence related to vaccination efficacy in patients with autoimmune disease and the effects of immunomodulatory therapy, with an aim to provide guidance and optimize the administration of vaccines in such individuals.

Intranasal formulations: promising strategy to deliver vaccines

INTRODUCTION

The emergence of new diseases and the lack of efficient vaccines against numerous non-treatable pathogens require the development of novel vaccination strategies. To date, only a few mucosal vaccines have been approved for humans. This was in part due to i) the use of live attenuated vaccines, which are not suitable for certain groups of individuals, ii) safety concerns derived from implementation in humans of some mucosal vaccines, iii) the poor stability, absorption and immunogenicity of antigens delivered by the mucosal route and iv) the limited number of available technologies to overcome the bottlenecks associated with mucosal antigen delivery. Recent advances make feasible the development of efficacious mucosal vaccines with adequate safety profile. Thus, currently intranasal vaccines represent an attractive and valid alternative to conventional vaccines.

AREAS COVERED

The present review is focused on the potentials and limitations of market-approved intranasal vaccines and promising candidates undergoing clinical investigations. Furthermore, emerging strategies to overcome main bottlenecks including efficient breaching of the mucosal barrier and safety concerns by implementation of new adjuvants and delivery systems are discussed.

EXPERT OPINION

The rational design of intranasal vaccines requires an in-depth understanding of the anatomic, physicochemical and barrier properties of the nasal mucosa, as well as the molecular mechanisms governing the activation of the local innate and adaptive immune system. This would provide the critical knowledge to establish effective approaches to deliver vaccine antigens across the mucosal barrier, supporting the stimulation of a long-lasting protective response at both mucosal and systemic levels. Current developments in the area of adjuvants, nanotechnologies and mucosal immunology, together with the identification of surface receptors that can be exploited for cell targeting and manipulating their physiological properties, will become instrumental for developing a new generation of more effective intranasal vaccines.

Neutropenia Precautions for Children Receiving Chemotherapy or Stem Cell Transplantation for Cancer

Infections in children and adolescents with cancer are a significant cause of morbidity and mortality, especially in those receiving chemotherapy who are neutropenic and/or immunocompromised. The aim of this article is to review existing evidence in order to provide a practice recommendation to prevent or minimize infections in neutropenic and/or immunocompromised patients receiving chemotherapy and/or stem cell transplant. Systematic reviews were undertaken and research was graded according to the Grading of Recommendations Assessment, Development, and Evaluation (GRADE) criteria. A variety of interventions are implemented to reduce infections in the neutropenic and/or immunocompromised population; however, few are supported by research evidence. Existing literature should continue to be reviewed to further identify interventions that can influence positive patient outcomes and provide opportunities for individuals in the medical field to work together to improve clinical care.

Live viral vaccines in immunocompromised patients

ABSTRACT: 

Live-attenuated viral vaccines (LAV) have been used safely for several decades in healthy individuals to protect against diseases with great success. In immunocompromised hosts their use is usually not recommended. We explore the use of currently available LAV, such as live-attenuated influenza, varicella–zoster virus, measles, mumps and rubella, oral polio, rotavirus, yellow fever virus vaccines, especially in patients with cancer, solid organ or hematopoietic stem cell transplant, HIV, and with acquired or congenital immunodeficiencies. Although evidence-based recommendations cannot currently be made, it is possible that LAV will be recommended in specific, well-defined situations in these immunocompromised patients in the future.

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.

A prospective study of chemotherapy immunologic effects and predictors of humoral influenza vaccine responses in a pediatric oncology cohort

BACKGROUND

Pediatric oncology patients represent a cohort of individuals uniquely at risk of complications from influenza, yet less likely to respond to the vaccine. It is not yet clear how to best protect this vulnerable population.

METHODS

We performed a prospective analysis of 177 pediatric oncology patients to define the predictors of influenza vaccine responses. Each variable was examined over three time points and a repeated measure analysis was performed.

RESULTS

Patients with ALL vaccinated during induction phase had superior influenza vaccine responses than those subjects vaccinated during post-induction or maintenance phases (P=0·0237). Higher aggregate HAI titer responses were associated with a higher baseline B-cell count (P=0·0240), and higher CD4 and CD8 influenza-specific T-cell responses, suggesting prior antigen exposure is a significant contributor. The solid tumor cohort had equivalent responses during all time frames of chemotherapy.

DISCUSSION

The optimal protection from influenza of pediatric patients on chemotherapy should include vaccination, but it is clear that not all patients produce high titers of antibodies after vaccination. This study identified biomarkers that could be used to individualize vaccine approaches. Immunologic predictors might have a role in targeting resources, as B-cell counts predicted of vaccine responses among the patients with ALL.

Vaccinations for healthcare personnel: update on influenza, hepatitis B, and pertussis

PURPOSE OF REVIEW

Healthcare personnel (HCP) are at risk for exposure to and transmission of potentially life-threatening vaccine preventable diseases to patients and colleagues. The Centers for Disease Control and Advisory Committee on Immunization Practices (ACIP) recommend routine influenza immunization and maintenance of immunity to hepatitis B and pertussis, among others. In this article, we aim to review recently approved influenza vaccines, as well as address some of the issues regarding hepatitis B and pertussis vaccinations in HCP.

RECENT FINDINGS

Several new formulations of influenza vaccines are now available, including quadrivalent vaccines and non-egg-based vaccines; their use in HCP requires further study. An alarming rise in pertussis rates has led to a revision of ACIP guidelines recommending vaccination for women during each pregnancy. Persistent lack of immunity to hepatitis B after vaccine series remains a problem for many HCP.

SUMMARY

Inactivated trivalent influenza vaccines remain the safest and most widely studied influenza vaccinations for healthcare workers. A pertussis booster in the form of Tdap is now recommended for most HCP. More studies are needed regarding the issue of nonresponders in HCP who receive the three-dose hepatitis B vaccine series, as there are some promising strategies available that may boost immune responses.

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.

Clinical and demographic characteristics of seasonal influenza in pediatric patients with cancer

BACKGROUND

Changes in oncology care and the diagnosis and management of influenza over the past several decades may have altered the epidemiology and outcomes of influenza in pediatric oncology patients.

METHODS

The clinical features and outcomes of 102 pediatric patients undergoing cancer therapy during 107 episodes of influenza between January 2002 and April 2009 were retrospectively ascertained.

RESULTS

Median age at the time of influenza was 7.2 years (interquartile range: 3.8-11.2 years); 46% of patients were male. Nineteen patients (18%) were recipients of hematopoietic stem cell transplants. Patients' median absolute neutrophil and lymphocyte counts were 1300/μL (interquartile range: 500-2967/μL) and 360/μL (interquartile range: 180-836/μL), respectively. Twelve patients (11%) had coinfections with influenza and one or more other respiratory pathogens. Influenza prompted patients' hospitalization during 64% of episodes, and 75% received antiviral therapy. Complications occurred in 30% of infections and serious complications occurred in 7%. Three patients died, but no deaths were directly attributable to influenza. Most patients had delays in cancer therapy; the median delay was 5 days. Neutropenia, concurrent infection, increasing age and having received hematopoietic stem cell transplant increased the risk of serious complications.

CONCLUSIONS

Advances in the management of pediatric cancer and influenza have not altered the epidemiology and outcome of influenza in oncology patients. Clinical features identify subgroups of patients with influenza who are at risk of poor outcomes and those with a good prognosis.

Live attenuated intranasal influenza vaccine

Annual vaccination is the most effective means of preventing and controlling influenza epidemics, and the traditional trivalent inactivated vaccine (TIV) is by far the most widely used. Unfortunately, it has a number of limitations, the most important of which is its poor immunogenicity in younger children and the elderly, the populations at greatest risk of severe influenza. Live attenuated influenza vaccine (LAIV) has characteristics that can overcome some of these limitations. It does not have to be injected because it is administered intranasally. It is very effective in children and adolescents, among whom it prevents significantly more cases of influenza than the traditional TIV. However, its efficacy in adults has not been adequately documented, which is why it has not been licensed for use by adults by the European health authorities. LAIV is safe and well tolerated by children aged > 2 y and adults, but some concerns arisen regarding its safety in younger children and subjects with previous asthma or with recurrent wheezing. Further studies are needed to solve these problems and to evaluate the possible role of LAIV in the annual vaccination of the general population.

Correlates of vaccine protection from influenza and its complications

Despite use of influenza vaccines for more than 65 y, influenza and its complications are a major cause of morbidity and mortality worldwide. Most deaths during influenza virus infections are due to underlying co-morbidities or secondary bacterial pneumonia. The measures of immune response currently used for licensure of influenza vaccines are relevant mainly for protection from viral infection in healthy adults. Development of new or improved influenza vaccines will require a definition of novel, and specific correlates of protection. These correlates should associate immune responses with outcomes that are relevant to specific risk groups, such as asthma exacerbation, hospitalization or disruptions to care or daily activities. Assessment of vaccine effectiveness for both viral and bacterial vaccines should include measures of impact on secondary bacterial pneumonia.

Immunization in special populations

In summary, immunizations in special populations require understanding the underlying disease and how it might affect the immune system's ability to mount an antibody response to vaccines or predispose certain patient populations to developing certain serious infections. There is still a great need for research on the optimal timing of vaccines after transplants, how to assess protection and development of a protective antibody response after immunization, and whether certain groups (eg, HIV) need to be revaccinated after a certain amount of time if their antibody levels decline. In addition, there are limited data on efficacy of the newer vaccines in these special patient populations, which also requires further investigation.