Influenza immunization for children

Intranasal administration of influenza vaccines: current status

AbstractThis review article focuses on intranasal immunisation against influenza,although it also encompasses antigen uptake and processing in the nasopharyngealpassages, host defence from influenza and current influenza vaccination practices.Improvement of current vaccination strategies is clearly required; current proceduresinvolve repeated annual injections that sometimes fail to protect the recipient. It isenvisaged that nonpercutaneous immunisation would be more attractive to potentialvaccinees, thus improving uptake and coverage. As well as satisfying noninvasivecriteria, intranasal influenza immunisation has a number of perceived immunologicaladvantages over current procedures. Perhaps one of the greatest attributes of thisapproach is its potential to evoke the secretion of haemagglutinin-specific IgAantibodies in the upper respiratory tract, the main site of viral infection. Inactivated influenza vaccines have the advantage that they have a long historyof good tolerability as injected immunogens, and in this respect are possibly morelikely to be licensed than attenuated viruses. Inert influenza vaccines are poormucosal immunogens, requiring several administrations, or prior immunologicalpriming, in order to engender significant antibody responses. The use of vaccinedelivery systems or mucosal adjuvants serves to appreciably improve theimmunogenicity of mucosally applied inactivated influenza vaccines. As is the casewhen they are introduced parenterally, inactivated influenza vaccines are relativelypoor stimulators of virus-specific cytotoxic T lymphocyte activity following nasalinoculation. Live attenuated intranasal influenza vaccines are at a far moreadvanced stage of clinical readiness (phase III versus phase I). With the use of liveattenuated vaccines, it is possible to stimulate mucosal and cell-mediatedimmunological responses of a similar kind to those elicited by natural influenzainfection. In children, recombinant live attenuated cold-adapted influenza viruses arewell tolerated. Moreover, cold-adapted influenza viruses usually stimulate protectiveimmunity following only a single nasal inoculation. Safety of recombinant liveattenuated cold-adapted influenza viruses has also been demonstrated in high riskindividuals with cystic fibrosis, asthma, cardiovascular disease and diabetes mellitus.They are not suitable for immunising immunocompromised patients, however, andare poorly efficacious in individuals with pre-existing immunity to strains closelyantigenically matched with the recombinant virus. According to the reviewedliterature, it is apparent that intranasal administration of vaccine as an aerosol issuperior to administration as nose drops. The information reviewed in this papersuggests that nasally administered influenza vaccines could make a substantialimpact on the human and economic cost of influenza.

Efficacy of injectable trivalent virosomal-adjuvanted inactivated influenza vaccine in preventing acute otitis media in children with recurrent complicated or noncomplicated acute otitis media

BACKGROUND

Most cases of acute otitis media (AOM) follow an upper respiratory infection due to viruses, including influenza viruses. As effective and safe influenza vaccines are available, their use has been considered among the possible measures of AOM prophylaxis.

OBJECTIVES

To evaluate the efficacy of an inactivated virosomal-adjuvanted influenza vaccine in preventing AOM in children with a history of noncomplicated recurrent AOM (rAOM) or rAOM complicated by spontaneous perforation.

METHODS

In this prospective, randomized, single-blinded, placebo-controlled study, 180 children aged 1 to 5 years with a history of rAOM and previously unvaccinated against influenza were randomized to receive the inactivated virosomal-adjuvanted subunit influenza vaccine (n = 90) or no treatment (n = 90), and AOM-related morbidity was monitored every 4 to 6 weeks for 6 months.

RESULTS

The number of children experiencing at least 1 AOM episode was significantly smaller in the vaccinated group (P < 0.001), as was the mean number of AOM episodes (P = 0.03), the mean number of AOM episodes without perforation (P < 0.001), and the mean number of antibiotic courses (P < 0.001); the mean duration of bilateral OME was significantly shorter (P = 0.03). The only factor that seemed to be associated with the significantly greater efficacy of influenza vaccine in preventing AOM was the absence of a history of recurrent perforation (crude odds ratio, P = 0.01; adjusted odds ratio, P = 0.006).

CONCLUSIONS

The intramuscular administration of injectable trivalent inactivated virosomal-adjuvanted influenza vaccine in children with a history of rAOM significantly reduces AOM-related morbidity. However, the efficacy of this preventive measure seems to be reduced in children with rAOM associated with repeated tympanic membrane perforation.

Disparities in influenza vaccination coverage rates by target group in five European countries: trends over seven consecutive seasons

BACKGROUND

The primary objective of this study was to measure influenza vaccination coverage rates in the general population, including children, and in high-risk groups of five European countries during the season 2007/2008. An additional aim was to analyze coverage trends over seven consecutive seasons and to gain an understanding of the primary drivers and barriers to immunization.

METHODS

Community-based telephone and mail surveys have been conducted in the UK, Germany, Italy, France, and Spain, yearly, since 2001/2002. Approximately 2,000 individuals per country and season were interviewed who were considered to be representative of the adult population aged 14 years and older. Data on the vaccination status of children were obtained by proxy interviews. The questionnaire used was essentially the same for all seven seasons. Five target groups were identified for the study: (1) persons aged > or = 65 years; (2) elderly suffering from a chronic illness; (3) patients suffering from a chronic illness; (4) persons working in the health care sector; (5) children.

RESULTS

In the season 2007/2008, vaccination coverage rates in the general population remained stable in Germany. Compared to the coverage rates of the previous season, increases of 3.7%, 2.0%, and 1.8% were observed for the UK, Spain, and France, respectively, while a decrease of -1.5% was observed for Italy. Across all five countries, vaccination rates in the predefined target groups decreased to some extent (elderly) or increased slightly (chronically ill and health care workers). Vaccination rates among children varied strongly between countries and ranged from 6.1% in UK to 19.3% in Germany. The most powerful motivation for getting vaccinated in all countries was advice from a family doctor (58.6%) and the perception of influenza as a serious illness (51.9%). The major reasons why individuals did not become vaccinated were (1) the feeling of not being likely to catch influenza (39.5%) and (2) never having considered the option of being vaccinated (35.8%).

CONCLUSIONS

The change in general influenza vaccination coverage in the 2007/2008 season compared to the previous season was small, but decreases were seen in some target groups. The underlying motivations for and against vaccination did not substantially change. An effort to activate those driving forces that would encourage vaccination as well as dealing with barriers that tend to prevent it may help enhance coverage rates in Europe in the future.

Immune response to influenza vaccine in pediatric patients with inflammatory bowel disease

BACKGROUND & AIMS

The aim of this study was to compare response to inactivated influenza vaccine in healthy children and pediatric patients with inflammatory bowel disease (IBD).

METHODS

A prospective, open-label, controlled clinical trial during influenza seasons of 2002-2004 was performed. Single-dose inactive trivalent influenza vaccine was administered. Immune response to vaccination was measured by pre-immunization and postimmunization hemagglutinin inhibition titers. A postimmunization hemagglutinin inhibition titer of 40 or higher was considered protective against influenza. IBD activity and adverse events were recorded.

RESULTS

Eighty subjects were enrolled (29 healthy controls, 51 IBD patients). One patient did not complete the study. Patients were divided into 3 subgroups: infliximab and immunomodulatory (16), immunomodulatory (20), and anti-inflammatory therapy (14). Immunomodulatory therapy included corticosteroids, 6-mercaptopurine, or methotrexate. Overall, there was a statistically significant decrease in immune response in patients compared with healthy controls who received 1 influenza vaccine antigen (B/Hong Kong, P = .0125). Patients receiving infliximab and immunomodulatory therapy were less likely to respond to 2 influenza vaccine antigens (A/New Caledonia/20/99 and B/Hong Kong/330/2001, P = .018 and .0002, respectively). Fifteen subjects (19%) reported 19 mild adverse events: 11 (14%) reported soreness at the site, 4 (5%) reported having a cold, 3 (4%) reported flu-like symptoms, and 1 (1%) reported a headache. The clinical activity of IBD was not affected by vaccination.

CONCLUSIONS

The serologic conversion rate to influenza vaccine in patients with IBD ranged from 33% to 85%. Patients on concomitant infliximab and immunomodulatory therapy are at risk of inadequate response to vaccination. The vaccine was safe and did not affect IBD activity.

Role of influenza vaccine for healthy children in the US

Influenza infection is associated with significant morbidity and mortality in adults, but the highest attack rates for influenza regularly occur in children, particularly those in preschool and elementary school. The consequences of influenza in this younger population - increased rate of hospitalization in those younger than 2 years of age and serious associated morbidity - have been underestimated. Children are also the critical link for spreading influenza in the community. Recent data suggest that mass influenza vaccination of healthy children would not only protect recipients, but also may reduce the burden of influenza throughout the community. During the past 3 decades, efforts to control influenza have focused on the use of an injectable trivalent inactivated vaccine (TIV) in high-risk persons. The vaccine is 'safe' and effective, but its acceptance and uptake by patients and healthcare providers have been modest at best. A new intranasal, live-attenuated, trivalent cold-adapted influenza virus vaccine (CAIV-T) [FluMist] is 'safe', well tolerated, immunogenic, and efficacious in preventing influenza illness in healthy children. Compared with TIV, CAIV-T is easier to administer and should be more readily acceptable, particularly for mass immunization campaigns. CAIV-T also induces a broader immune response and has demonstrated protection against at least three different variant influenza strains. This vaccine is particularly well suited for routine immunization of children and thus offers the potential for greatly improved control of influenza. However, the acquisition cost per single dose of FluMist for the 2003-4 season ( approximate, equals 46 US dollars) significantly hampered its uptake both by practitioners and by managed care organizations, even despite a later approximate, equals 25 US dollars rebate offer. For the 2004-5 season, CAIV-T is likely to be only modestly more expensive (average wholesale price: 16.50 US dollars for non-returnable doses, 23 US dollars for returnable doses) than TIV. The practitioner must consider the benefits of FluMist compared with its likely higher vaccine cost and the issues of reimbursement among multiple insurers.

Protective efficacy of intranasal cold-adapted influenza A/New Caledonia/20/99 (H1N1) vaccines comprised of egg- or cell culture-derived reassortants

Live, cold-adapted, temperature-sensitive (ca/ts) Russian influenza A vaccines are prepared in eggs by a 6:2 gene reassortment of the ca/ts donor strain A/Leningrad/134/17/57 (H2N2) (Len/17) with a current wild-type (wt) influenza A strain contributing hemagglutinin (HA) and neuraminidase (NA) genes. However, egg-derived reassortant vaccines are potentially more problematic to manufacture in large quantities than vaccines from cell-based procedures. To compare egg- and cell culture-derived reassortant vaccines, we prepared in Madin Darby canine kidney (MDCK) cells two cloned, ca/ts reassortants (25M/1, 39E/2) derived from Len/17 and a wt reference strain A/New Caledonia/20/99 (H1N1) (NC/wt). Both 25M/1 and 39E/2 reassortants preserved the ca/ts phenotype and mutations described for internal genes of the A/Len/17 parent. When compared to a commercial, egg-derived ca/ts Russian A/17/NC/99/145 (H1N1) New Caledonia vaccine (NC/145), the MDCK-derived reassortant 39E/2 vaccine conferred similar levels of protection in ferrets challenged i.n. with 7 x 10(10) pfu of NC/wt. In a dose-ranging study, the protective vaccine dose for 50% of ferrets (PD50) was less than 1.2 x 10(4) pfu for the 25M/1 vaccine derived by recombination and amplification in MDCK cells. Clonal isolates of ca/ts influenza A/New Caledonia/20/99 (H1N1) obtained by recombination and amplification entirely in MDCK cells can be highly protective i.n. vaccines.

Multiple amino acid residues confer temperature sensitivity to human influenza virus vaccine strains (FluMist) derived from cold-adapted A/Ann Arbor/6/60

FluMist influenza A vaccine strains contain the PB1, PB2, PA, NP, M, and NS gene segments of ca A/AA/6/60, the master donor virus-A strain. These gene segments impart the characteristic cold-adapted (ca), attenuated (att), and temperature-sensitive (ts) phenotypes to the vaccine strains. A plasmid-based reverse genetics system was used to create a series of recombinant hybrids between the isogenic non-ts wt A/Ann Arbor/6/60 and MDV-A strains to characterize the genetic basis of the ts phenotype, a critical, genetically stable, biological trait that contributes to the attenuation and safety of FluMist vaccines. PB1, PB2, and NP derived from MDV-A each expressed determinants of temperature sensitivity and the combination of all three gene segments was synergistic, resulting in expression of the characteristic MDV-A ts phenotype. Site-directed mutagenesis analysis mapped the MDV-A ts phenotype to the following four major loci: PB1(1195) (K391E), PB1(1766) (E581G), PB2(821) (N265S), and NP(146) (D34G). In addition, PB1(2005) (A661T) also contributed to the ts phenotype. The identification of multiple genetic loci that control the MDV-A ts phenotype provides a molecular basis for the observed genetic stability of FluMist vaccines.

Influenza virus vaccines in children and their impact on the incidence of otitis media

Otitis media has been identified as the most frequent reason for outpatient antibiotic therapy. Several studies have linked viral respiratory infections with bacterial otitis media. In light of rising concerns about antibiotic resistance, the possibility of reducing the incidence of otitis media through vaccination against respiratory viruses has received increasing attention. This article reviews inactivated and live attenuated influenza virus vaccines and their possible impact on the incidence of otitis media. Inactivated and live attenuated influenza virus vaccines are safe and immunogenic in children older than 6 months and are linked to a decrease in the incidence of otitis media. Influenza vaccination of infants younger than 6 months has resulted in less predictable immunogenicity and deserves further investigation.

Future vaccines: recent advances and future prospects

The 20th century has witnessed the introduction of over 20 vaccines that prevent or even conquer diseases such as smallpox, polio, and measles. The continued threat of infectious diseases demands the creation of many more vaccines, especially against common respiratory and gastrointestinal pathogens. Thanks to recent advances in molecular biology, immunology, and adjuvant technology, the next decade likely will bring a vaccine for HIV/AIDS also. We enter the 21st century with a tempered optimism, proud of past achievements, but mindful of the challenges that lie ahead.

Cost-effectiveness analysis of an intranasal influenza vaccine for the prevention of influenza in healthy children

OBJECTIVE

Intranasal influenza vaccine has proven clinical efficacy and may be better tolerated by young children and their families than an injectable vaccine. This study determined the potential cost-effectiveness (CE) of an intranasal influenza vaccine among healthy children.

METHODS

We conducted a CE analysis of data collected between 1996 and 1998 during a prospective 2-year efficacy trial of intranasal influenza vaccine, supplemented with data from the literature. The CE analysis included both direct and indirect costs. We enrolled 1602 healthy children aged 15 to 71 months in year 1, 1358 of whom were enrolled in year 2. One or 2 doses of intranasal influenza vaccine or placebo were administered to measure the cost per febrile influenza-like illness (ILI) day avoided.

RESULTS

During the 2-year study period, vaccinated children had an average of 1.2 fewer ILI fever days/child than unvaccinated children. In an individual-based vaccine delivery scenario with vaccine given twice in the first year and once each year thereafter at an assumed base case total cost of $20 for the vaccine and its administration (ie, per dose), CE was approximately $30/febrile ILI day avoided. CE ranged from $10 to $69/febrile ILI day avoided at $10 to $40/dose, respectively. In a group-based delivery scenario, vaccination was cost saving compared with placebo and remained so if vaccine cost was <$28 (the break-even price per dose). In the individual-based scenario, vaccination was cost saving if vaccine cost was <$5. In this scenario, nearly half of lost productivity in the vaccine group was attributable to vaccine visits, which overshadowed the relatively modest savings in ILI-associated costs averted.

CONCLUSIONS

Routine use of intranasal influenza vaccine among healthy children may be cost-effective and may be maximized by using group-based vaccination approaches. cost-effectiveness, influenza, vaccine, children.

Influenza: vaccination and treatment

Few conditions exert such an enormous toll of absenteeism, suffering, medical consultations, hospitalization, death and economic loss as influenza. Patients at high risk of complications and mortality include the elderly and those with pre-existing cardiopulmonary disease. The outbreak in 1997 in Hong Kong, of avian H5N1 influenza in man, which resulted in six deaths among 18 hospitalized cases, and the recent isolation of H9N2 viruses from two children in Hong Kong, are reminders that preparation must be made for the next pandemic. Since the 1970s, efforts to control influenza have mostly focussed on the split product and surface antigen vaccines. These vaccines are of proven efficacy in healthy adults and are effective in elderly people with and without medical conditions putting them at high risk of complications and death following influenza infection. However, vaccine coverage is patchy and often low, and outbreaks of influenza are not uncommon in well-immunized residents of nursing homes. New vaccines and methods of vaccine delivery are being developed in attempts to overcome the limitations of existing vaccines. The antiviral drugs amantadine and rimantadine were developed in the 1960s, but have not been used widely due to their spectrum of activity, rapid emergence of resistance, and adverse effects associated with amantadine. The site of enzyme activity of the influenza neuraminidase is highly conserved between types, subtypes and strains of influenza and has emerged as the target of an exciting new class of antiviral agents that are effective both prophylactically and as therapy.

Comparison of immunogenicity and safety of a virosome influenza vaccine with those of a subunit influenza vaccine in pediatric patients with cystic fibrosis

The objective of this study was to compare the immunogenicity and safety of a single-dose regimen and a two-dose regimen of a trivalent virosome influenza vaccine (Inflexal Berna V) with those of a trivalent subunit influenza vaccine (Influvac) in children and adolescents with cystic fibrosis (CF). In an open, randomized, multicenter study with parallel groups, 11 young children with CF (1 to 6 years old) and 53 older children and adolescents with CF (>6 years old) were randomly assigned to one of the following immunization regimens: virosome vaccine at 0.5 ml on study day 0 or 0.25 ml on days 0 and 28 or a standard regimen of subunit vaccine, i. e., 0.5 ml on day 0 for older children and 0.25 ml on days 0 and 28 for younger children. Safety assessments, i.e., recording of systemic and local adverse events (AEs) and vital signs, were made for a 5-day observation period after each immunization. Hemagglutination inhibition (HI) titers were determined at baseline and 4 weeks after the single-dose and the two-dose immunizations, respectively. Immunogenicity was assessed according to the criteria of the European Agency for the Evaluation of Medicinal Products (EMEA). Both vaccines induced comparable HI antibody titers. Seroconversion (> or =4-fold rise in HI antibody titers, reaching a titer of > or =1:40) was achieved in 41 to 100% of the participants. Seroprotection (HI titer, > or =1:40) and a >2.5-fold increase in geometric mean titers were achieved in 100% of the participants. Thus, all three EMEA requirements for influenza vaccine efficacy were met by all treatment groups and for both vaccines. The virosome vaccine, when administered as a single dose, seemed to induce superior immunogenicity compared with the standard pediatric two-dose regimen. Totals of 42 and 57% of vaccinees receiving virosome and subunit vaccines, respectively, reported at least one local AE (predominantly pain). Totals of 84 and 71% of subjects receiving virosome and subunit vaccines, respectively, complained in response to questions of at least one systemic AE (mainly cough, fatigue, coryza, or headache). The majority of events were mild or moderate and lasted 1 or 2 days only. No obvious relationship was found between AE reporting rate and vaccine formulation, age group, or dose regimen. The relatively high AE reporting rate seemed to be partly related to the symptomatology of the underlying CF disease. In summary, the virosome and subunit vaccines induced in both age groups and against all three influenza strains an efficient immune response and were well tolerated by the children and adolescents with CF.

Vaccines and therapeutics against influenza virus infections

BACKGROUND

Vaccination prior to epidemic season is the best measure to control influenza virus infection; however, there are several issues to be considered regarding influenza vaccines in Japan. In the present review, current issues regarding influenza vaccine in Japan are described, as well as the future prospects of vaccine development. As well as vaccination, anti-influenza agents such as amantadine are now available in Japan. Furthermore, neuraminidase inhibitors are expected to appear in the market in near future. These anti-influenza agents represent new options for influenza control.

CONCLUSIONS

Vaccination and antiviral agents are a major armamentarium against influenza infections. Thus, exploratory studies on novel forms of vaccine and anti-influenza drugs should help to prepare against pandemics that must emerge in near future.

Potential cost savings attributable to influenza vaccination of school-aged children

OBJECTIVE

To analyze the costs and benefits of influenza vaccination of healthy school-aged children.

DESIGN

The analysis was based on data from the literature. Total costs included direct medical costs for vaccination, physician visits, and treatment as well as indirect costs. Indirect costs were in the form of lost productivity when working parents stayed home to care for ill children or to take children to an office for vaccination. The total costs of vaccination strategies were compared with the total cost of not vaccinating. For the base case, the vaccine was assumed to have no effect on rates of otitis media.

SETTING

Two hypothetical scenarios were investigated 1) individual-initiated vaccination and 2) vaccination in a group-based setting. The former scenario required the child to be accompanied to a clinic by a parent during usual work hours.

RESULTS

Vaccination resulted in a net savings per child vaccinated of $4 for individual-initiated vaccination and of $35 for group-based vaccination. The savings were caused primarily by averted indirect costs. Moderate increases in the cost of vaccination or reductions in the rate of influenza would eliminate the savings for individual-initiated vaccination but not for group-based vaccination. Alternatively, if influenza vaccination was effective in reducing rates of otitis media, the net savings from vaccination would be substantially higher than the base case.

CONCLUSION

Vaccination of school-aged children against influenza could have substantial financial benefits to society, especially if performed in a group-based setting. influenza, cost-effectiveness, vaccination, children, cost.