Emerging vaccines for influenza

Dual N-linked glycosylation at residues 133 and 158 in the hemagglutinin are essential for the efficacy of H7N9 avian influenza virus like particle vaccine in chickens and mice

H7N9 subtype avian influenza virus (AIV) poses a great challenge to poultry industry. Virus-like particle (VLP) is a prospective alternative for the traditional egg-based influenza vaccines. N-linked glycosylation (NLG) regulates the efficacy of influenza vaccines, whereas the impact of NLG modifications on the efficacy of influenza VLP vaccines remains unclear. Here, H7N9 VLPs were assembled in insect cells through co-infection with the baculoviruses expressing the NLG-modified hemagglutinin (HA), neuraminidase and matrix proteins, and the VLP vaccines were assessed in chickens and mice. NLG modifications significantly enhanced hemagglutination-inhibition and virus neutralization antibody responses in mice, rather than in chickens, because different immunization strategies were used in these animal models. The presence of dual NLG at residues 133 and 158 significantly elevated HA-binding IgG titers in chickens and mice. The VLP vaccines conferred complete protection and significantly suppressed virus replication and lung pathology post challenge with H7N9 viruses in chickens and mice. VLP immunization activated T cell immunity-related cytokine response and inhibited inflammatory cytokine response in mouse lung. Of note, the presence of dual NLG at residues 133 and 158 optimized the capacity of the VLP vaccine to stimulate interleukin-4 expression, inhibit virus shedding or alleviate lung pathology in chickens or mice. Intriguingly, the VLP vaccine with NLG addition at residue 133 provided partial cross-protection against the H5Nx subtype AIVs in chickens and mice. In conclusion, dual NLG at residues 133 and 158 in HA can be potentially used to enhance the efficacy of H7N9 VLP vaccines in chickens and mammals.

Evaluation of Protective Efficacy of Influenza Virus Like Particles Prepared from H5N1 Virus of Clade 2.2.1.2 in Chickens

Highly pathogenic Avian Influenza (HPAI) viruses continue to cause severe economic losses in poultry species worldwide. HPAI virus of subtype H5N1 was reported in Egypt in 2006, and despite vaccination efforts, the virus has become endemic. The current study aims to evaluate the efficacy of a virus-like particle (VLP) based vaccine in vivo using specific pathogen-free (SPF) chickens. The vaccine was prepared from the HPAI H5N1 virus of clade 2.2.1.2 using the baculovirus expression system. The VLPs were quantitated and characterized, including electron microscopy. In addition, the protection level of the VLPs was evaluated by using two different regimens, including one dose and two-dose vaccinated groups, which gave up to 70% and 100% protection level, respectively. The results of this study emphasize the potential usefulness of the VLPs-based vaccine as an alternative vaccine candidate for the control of AIV infection in poultry.

Repositioning Drugs on Human Influenza A Viruses Based on a Novel Nuclear Norm Minimization Method

Influenza A viruses, especially H3N2 and H1N1 subtypes, are viruses that often spread among humans and cause influenza pandemic. There have been several big influenza pandemics that have caused millions of human deaths in history, and the threat of influenza viruses to public health is still serious nowadays due to the frequent antigenic drift and antigenic shift events. However, only few effective anti-flu drugs have been developed to date. The high development cost, long research and development time, and drug side effects are the major bottlenecks, which could be relieved by drug repositioning. In this study, we proposed a novel antiviral Drug Repositioning method based on minimizing Matrix Nuclear Norm (DRMNN). Specifically, a virus-drug correlation database consisting of 34 viruses and 205 antiviral drugs was first curated from public databases and published literature. Together with drug similarity on chemical structure and virus sequence similarity, we formulated the drug repositioning problem as a low-rank matrix completion problem, which was solved by minimizing the nuclear norm of a matrix with a few regularization terms. DRMNN was compared with three recent association prediction algorithms. The AUC of DRMNN in the global fivefold cross-validation (fivefold CV) is 0.8661, and the AUC in the local leave-one-out cross-validation (LOOCV) is 0.6929. Experiments have shown that DRMNN is better than other algorithms in predicting which drugs are effective against influenza A virus. With H3N2 as an example, 10 drugs most likely to be effective against H3N2 viruses were listed, among which six drugs were reported, in other literature, to have some effect on the viruses. The protein docking experiments between the chemical structure of the prioritized drugs and viral hemagglutinin protein also provided evidence for the potential of the predicted drugs for the treatment of influenza.

Haemagglutinin displayed on the surface of Lactococcus lactis confers broad cross-clade protection against different H5N1 viruses in chickens

Background

The highly pathogenic avian influenza (HPAI) H5N1 virus poses a potential threat to the poultry industry. The currently available avian influenza H5N1 vaccines for poultry are clade-specific. Therefore, an effective vaccine for preventing and controlling H5N1 viruses belonging to different clades needs to be developed.

Results

Recombinant L. lactis/pNZ8148-Spax-HA was generated, and the influenza virus haemagglutinin (HA) protein of A/Vietnam/1203/2004 (H5N1) was displayed on the surface of Lactococcus lactis (L. lactis). Spax was used as an anchor protein. Chickens vaccinated orally with unadjuvanted L. lactis/pNZ8148-Spax-HA could produce significant humoral and mucosal responses and neutralizing activities against H5N1 viruses belonging to different clades. Importantly, unadjuvanted L. lactis/pNZ8148-Spax-HA conferred cross-clade protection against lethal challenge with different H5N1 viruses in the chicken model.

Conclusion

This study provides insights into the cross-clade protection conferred by unadjuvanted L. lactis/pNZ8148-Spax-HA, and the results might help the establishment of a promising platform for the development of a safe and effective H5N1 cross-clade vaccine for poultry.

A single dose of a vesicular stomatitis virus-based influenza vaccine confers rapid protection against H5 viruses from different clades

The avian influenza virus outbreak in 1997 highlighted the potential of the highly pathogenic H5N1 virus to cause severe disease in humans. Therefore, effective vaccines against H5N1 viruses are needed to counter the potential threat of a global pandemic. We have previously developed a fast-acting and efficacious vaccine against Ebola virus (EBOV) using the vesicular stomatitis virus (VSV) platform. In this study, we generated recombinant VSV-based H5N1 influenza virus vectors to demonstrate the feasibility of this platform for a fast-acting pan-H5 influenza virus vaccine. We chose multiple approaches regarding antigen design and genome location to define a more optimized vaccine approach. After the VSV-based H5N1 influenza virus constructs were recovered and characterized in vitro, mice were vaccinated by a single dose or prime/boost regimen followed by challenge with a lethal dose of the homologous H5 clade 1 virus. We found that a single dose of VSV vectors expressing full-length hemagglutinin (HAfl) were sufficient to provide 100% protection. The vaccine vectors were fast-acting as demonstrated by uniform protection when administered 3 days prior to lethal challenge. Moreover, single vaccination induced cross-protective H5-specific antibodies and protected mice against lethal challenge with various H5 clade 2 viruses, highlighting the potential of the VSV-based HAfl as a pan-H5 influenza virus emergency vaccine.

Vaccines for the elderly

Vaccination is the most efficient strategy to prevent infectious disease. The increased vulnerability to infection of the elderly makes them a particularly important target population for vaccination. However, most vaccines are less immunogenic and efficient in the elderly because of age-related changes in the immune system. Vaccination against influenza, Streptococcus pneumoniae and varicella zoster virus is recommended for the elderly in many countries. Various strategies such as the use of adjuvants and novel administration routes are pursued to improve influenza vaccination for the elderly and recent developments in the field of pneumococcal vaccination led to the licensure of protein-conjugated polysaccharide vaccines containing up to 13 serotypes. As antibody titres are generally lower in the elderly and-particularly for inactivated vaccines-decline fast in the elderly, regular booster immunizations, for example against tetanus, diphtheria and, in endemic areas, tick-borne encephalitis, are essential during adulthood to ensure protection of the elderly. With increasing health and travel opportunities in old age the importance of travel vaccines for persons over the age of 60 is growing. However, little is known about immunogenicity and efficacy of travel vaccines in this age group. Despite major advances in the field of vaccinology over the last decades, there are still possibilities for improvement concerning vaccines for the elderly. Novel approaches, such as viral vectors for antigen delivery, DNA-based vaccines and innovative adjuvants, particularly toll-like receptor agonists, will help to achieve optimal protection against infectious diseases in old age.

Systems biology as a conceptual framework for research in family medicine; use in predicting response to influenza vaccination

AIM

To introduce systems biology as a conceptual framework for research in family medicine, based on empirical data from a case study on the prediction of influenza vaccination outcomes. This concept is primarily oriented towards planning preventive interventions and includes systematic data recording, a multi-step research protocol and predictive modelling.

BACKGROUND

Factors known to affect responses to influenza vaccination include older age, past exposure to influenza viruses, and chronic diseases; however, constructing useful prediction models remains a challenge, because of the need to identify health parameters that are appropriate for general use in modelling patients' responses.

METHODS

The sample consisted of 93 patients aged 50-89 years (median 69), with multiple medical conditions, who were vaccinated against influenza. Literature searches identified potentially predictive health-related parameters, including age, gender, diagnoses of the main chronic ageing diseases, anthropometric measures, and haematological and biochemical tests. By applying data mining algorithms, patterns were identified in the data set. Candidate health parameters, selected in this way, were then combined with information on past influenza virus exposure to build the prediction model using logistic regression.

FINDINGS

A highly significant prediction model was obtained, indicating that by using a systems biology approach it is possible to answer unresolved complex medical uncertainties. Adopting this systems biology approach can be expected to be useful in identifying the most appropriate target groups for other preventive programmes.

Superior immunogenicity of seasonal influenza vaccines containing full dose of MF59 (®) adjuvant: results from a dose-finding clinical trial in older adults

BACKGROUND

MF59-adjuvanted influenza vaccines have superior immunogenicity in older adults compared with non-adjuvanted vaccines. We assessed whether changing formulation (i.e., increasing H3N2 antigen or decreasing the quantity of adjuvant) of the licensed, MF59-adjuvanted trivalent influenza subunit vaccine Fluad (®) (Novartis Vaccines and Diagnostics) improves the risk-benefit profile in vaccinees aged ≥ 65 years.

RESULTS

A significant dose-response relationship was observed between antibody levels and MF59 dose; full dose formulations elicited the strongest immune responses, meeting immunogenicity licensure criteria by Day 8. Doubling H3N2 antigen content did not increase the response to this antigen. Increased frequency of circulating CD4+ T-cells specific for vaccine antigens were detected by Day 8; magnitude and functional profile of the CD4+ T-cell response was comparable across the different vaccination groups. Mild to moderate solicited local reactions were more common with vaccines formulated with higher doses of MF59 (®) , but there were no MF59- or antigen dose-related increase in the frequency of solicited systemic reactions or unsolicited adverse events and serious adverse events.

METHODS

We report on 357 subjects who received one of eight intramuscular vaccine formulations. Hemagglutination-inhibiting antibodies were assayed on Days 1, 8 and 22; magnitude and functional profile of CD4+ T-cell responses to vaccine antigens were assessed in subsets. Solicited adverse reactions were reported via diary cards for seven days after vaccination and spontaneous adverse events were monitored throughout the study.

CONCLUSION

This study confirms that the current formulation is the optimal one for MF59-adjuvanted influenza vaccine for use in older adults.

Addition of the immunostimulatory oligonucleotide IMT504 to a seasonal flu vaccine increases hemagglutinin antibody titers in young adult and elder rats, and expands the anti-hemagglutinin antibody repertoire

Flu vaccines are partially protective in infants and elder people. New adjuvants such as immunostimulatory oligonucleotides (ODNs) are strong candidates to solve this problem, because a combination with several antigens has demonstrated effectiveness. Here, we report that IMT504, the prototype of a major class of immunostimulatory ODNs, is a potent adjuvant of the influenza vaccine in young adult and elderly rats. Flu vaccines that use virosomes or whole viral particles as antigens were combined with IMT504 and injected in rats. Young adult and elderly animals vaccinated with IMT504-adjuvated preparations reached antibody titers 20-fold and 15-fold higher than controls, respectively. Antibody titers remained high throughout a 120 day-period. Animals injected with the IMT504-adjuvated vaccine showed expansion of the anti-hemagglutinin antibody repertoire and a significant increase in the antibody titer with hemagglutination inhibition capacity when confronted to viral strains included or not in the vaccine. This indicates that the addition of IMT504 in flu vaccines may contribute to the development of significant cross-protective immune response against shifted or drifted flu strains.

Human influenza vaccines and assessment of immunogenicity

Influenza is responsible for the infection of approximately 20% of the population every season and for an annual death toll of approximately half a million people. The most effective means for controlling infection and thereby reducing morbidity and mortality is vaccination by injection with an inactivated vaccine, or by intranasal administration of a live-attenuated vaccine. Protection is not always optimal and there is a need for the development of new vaccines with improved efficacy and for the expansion of enrollment into vaccination programs. An overview of old and new vaccines is presented. Methods of monitoring immune responses such as hemagglutination-inhibition, ELISA and neutralization tests are evaluated for their accuracy in the assessment of current and new-generation vaccines.

Advances in the vaccination of the elderly against influenza: role of a high-dose vaccine

On 23 December 2009, the US FDA approved Fluzone® High Dose, a high-dose formulation of the trivalent inactivated influenza vaccine, for prevention of influenza in people 65 years of age and older. As it was approved via an accelerated process designed to allow expeditious availability of safe and effective products with promise to treat or prevent serious or life-threatening diseases, the manufacturer is required to conduct further studies to demonstrate effectiveness. Although these studies are underway, a recently completed randomized, controlled trial demonstrated that this vaccine, containing four-times more hemagglutinin than standard-dose inactivated influenza vaccines, can produce an enhanced immunologic response in subjects of 65 years of age and older, while maintaining a favorable safety profile. This article introduces the vaccine, presents currently available safety and immunogenicity data, discusses current recommendations for use, and proposes what we can expect in the coming years.

Inactivated split-virion seasonal influenza vaccine (Fluarix): a review of its use in the prevention of seasonal influenza in adults and the elderly

Fluarix is a trivalent, inactivated, split-virion influenza vaccine containing 15 microg haemagglutinin from each of the three influenza virus strains (including an H1N1 influenza A virus subtype, an H3N2 influenza A virus subtype and an influenza B virus) that are expected to be circulating in the up-coming influenza season. Fluarix is highly immunogenic in healthy adults and elderly, and exceeds the criteria that make it acceptable for licensure in various regions (including the US and Europe). In a large, phase III, placebo-controlled, double-blind trial conducted in the US (2004/2005) in subjects aged 18-64 years, postvaccination seroconversion rates against the H1N1, H3N2 and B antigens were 60-78% and respective postvaccination seroprotection rates were 97-99% in Fluarix recipients. Another phase III trial conducted in the US (2005/2006) established the noninferiority of Fluarix versus another trivalent inactivated influenza virus vaccine in subjects aged >or=18 years, including a subgroup of elderly subjects. In annual European registration trials, Fluarix has consistently exceeded the immunogenicity criteria set by the EU Committee for Medicinal Products for Human Use for adults and the elderly. Fluarix demonstrated immunogenicity in small, open-label studies in at-risk subjects. During a year when the vaccine was well matched to the circulating strain, Fluarix demonstrated efficacy against culture-confirmed influenza A and/or B in a placebo-controlled trial in adults aged 18-64 years. In addition, Fluarix vaccination of pregnant women demonstrated efficacy in reducing the rate of laboratory-confirmed influenza in the infants and reducing febrile respiratory illnesses in the mothers and their new-born infants in a randomized trial. Fluarix was generally well tolerated in adults and the elderly in well designed clinical trials and in the annual European registration trials, with most local and general adverse events being transient and mild to moderate in intensity. The most common adverse reactions in recipients of Fluarix were pain, redness or swelling at the injection site, muscle aches, fatigue, headache and arthralgia. In conclusion, Fluarix is an important means of decreasing the impact of seasonal influenza viruses on adults and the elderly.

The need for quadrivalent vaccine against seasonal influenza

Seasonal influenza epidemics represent a substantial public health burden, causing significant morbidity and mortality. Influenza in humans can be caused by influenza type A and type B viruses, and although influenza A is responsible for the majority of seasonal influenza infections, influenza B disease is common in children and young adults, and causes seasonal epidemics every 2-4 years. Influenza strains circulating during a seasonal epidemic may be influenza type A strains A/H1N1 and A/H3N2, strains of influenza B lineages B/Victoria and B/Yamagata, or any combination of these. The morbidity and mortality burden of influenza infections means that public health agencies worldwide recommend vaccination to try and protect against seasonal epidemics. The World Health Organization (WHO) and, in the United States of America (USA), the Food and Drug Administration (FDA), recommend trivalent seasonal influenza vaccines containing the two main influenza type A strains and, due to its lesser but still important prevalence, one influenza type B strain. There is little or no cross-reactive protection between the influenza B lineages: this means that good protection against the circulating virus relies on correctly predicting the prevalent influenza B lineage in any season. This has proved to be reliant on chance, and little or no protection has been provided in the USA by the trivalent vaccines against the circulating influenza B virus in 5 of the 10 seasons between 2001 and 2010. There is, therefore, a clear need for a quadrivalent influenza vaccine, containing influenza A/H1N1, A/H3N2, and B/Victoria and B/Yamagata lineage strains, to improve protection against influenza B virus and reduce the morbidity of influenza B infection.

Prediction of influenza vaccination outcome by neural networks and logistic regression

The major challenge in influenza vaccination is to predict vaccine efficacy. The purpose of this study was to design a model to enable successful prediction of the outcome of influenza vaccination based on real historical medical data. A non-linear neural network approach was used, and its performance compared to logistic regression. The three neural network algorithms were tested: multilayer perceptron, radial basis and probabilistic in conjunction with parameter optimization and regularization techniques in order to create an influenza vaccination model that could be used for prediction purposes in the medical practice of primary health care physicians, where the vaccine is usually dispensed. The selection of input variables was based on a model of the vaccine strain which has frequently been changed and on which a poor influenza vaccine response is expected. The performance of models was measured by the average hit rate of negative and positive vaccine outcome. In order to test the generalization ability of the models, a 10-fold cross-validation procedure revealed that the model obtained by multilayer perceptron produced the highest average hit rate among neural network algorithms, and also outperformed the logistic regression model with regard to sensitivity and specificity. Sensitivity analysis was performed on the best model and the importance of input variables was discussed. Further research should focus on improving the performance of the model by combining neural networks with other intelligent methods in this field.

Influenza vaccines: from surveillance through production to protection

Influenza is an important contributor to population and individual morbidity and mortality. The current influenza pandemic with novel H1N1 has highlighted the need for health care professionals to better understand the processes involved in creating influenza vaccines, both for pandemic as well as for seasonal influenza. This review presents an overview of influenza-related topics to help meet this need and includes a discussion of the burden of disease, virology, epidemiology, viral surveillance, and vaccine strain selection. We then present an overview of influenza vaccine-related topics, including vaccine production, vaccine efficacy and effectiveness, influenza vaccine misperceptions, and populations that are recommended to receive vaccination. English-language articles in PubMed published between January 1, 1970, and October 7, 2009, were searched using key words human influenza, influenza vaccines, influenza A, and influenza B.

Rapid typing and subtyping of vaccine strains of the influenza virus with high resolution mass spectrometry

The application of high-resolution mass spectrometry to type and subtype strains of the influenza virus within recent recommended vaccine formulations is described. Proteolytic digests of whole virus or separated hemagglutinin antigen generate conserved signature peptides of unique mass that can be used to characterise each component virus in a rapid and direct manner by the detection of their ions alone. The approach is demonstrated for two type A strains and one type B strain of human influenza viruses present in recommended seasonal vaccines in the northern and southern hemispheres from 2007 through 2010.

Evidence for a novel gene associated with human influenza A viruses

BACKGROUND

Influenza A virus genomes are comprised of 8 negative strand single-stranded RNA segments and are thought to encode 11 proteins, which are all translated from mRNAs complementary to the genomic strands. Although human, swine and avian influenza A viruses are very similar, cross-species infections are usually limited. However, antigenic differences are considerable and when viruses become established in a different host or if novel viruses are created by re-assortment devastating pandemics may arise.

RESULTS

Examination of influenza A virus genomes from the early 20th Century revealed the association of a 167 codon ORF encoded by the genomic strand of segment 8 with human isolates. Close to the timing of the 1948 pseudopandemic, a mutation occurred that resulted in the extension of this ORF to 216 codons. Since 1948, this ORF has been almost totally maintained in human influenza A viruses suggesting a selectable biological function. The discovery of cytotoxic T cells responding to an epitope encoded by this ORF suggests that it is translated into protein. Evidence of several other non-traditionally translated polypeptides in influenza A virus support the translation of this genomic strand ORF. The gene product is predicted to have a signal sequence and two transmembrane domains.

CONCLUSION

We hypothesize that the genomic strand of segment 8 of encodes a novel influenza A virus protein. The persistence and conservation of this genomic strand ORF for almost a century in human influenza A viruses provides strong evidence that it is translated into a polypeptide that enhances viral fitness in the human host. This has important consequences for the interpretation of experiments that utilize mutations in the NS1 and NEP genes of segment 8 and also for the consideration of events that may alter the spread and/or pathogenesis of swine and avian influenza A viruses in the human population.

Influenza in immunosuppressed populations: a review of infection frequency, morbidity, mortality, and vaccine responses

Patients that are immunosuppressed might be at risk of serious influenza-associated complications. As a result, multiple guidelines recommend influenza vaccination for patients infected with HIV, who have received solid-organ transplants, who have received haemopoietic stem-cell transplants, and patients on haemodialysis. However, immunosuppression might also limit vaccine responses. To better inform policy, we reviewed the published work relevant to incidence, outcomes, and prevention of influenza infection in these patients, and in patients being treated chemotherapy and with systemic corticosteroids. Available data suggest that most immunosuppressed populations are indeed at higher risk of influenza-associated complications, have a general trend toward impaired humoral vaccine responses (although these data are mixed), and can be safely vaccinated--although longitudinal data are largely lacking. Randomised clinical trial data were limited to one study of HIV-infected patients with high vaccine efficacy. Better trial data would inform vaccination recommendations on the basis of efficacy and cost in these at-risk populations.

Baculovirus vector as a delivery vehicle for influenza vaccines

The baculovirus vector has emerged as an efficient delivery vehicle for influenza vaccines. In addition to the ease and safety in expeditious production, recent improvements in baculovirus engineering to display foreign proteins on the surface and to express transgenes with suitable promoters in various cell lines have become milestones in the development of the baculovirus expression system. Surface-displayed and shuttle promoter-mediated baculovirus vaccines for influenza present advantages in immunogenicity and safety, as studied in several animal models. A variety of strategies, including the modification of envelope proteins for surface display, the selection of novel promoters for in vivo transductions and advancements in downstream processing, aid the improvement of baculovirus-based influenza vaccines and represent progress toward next-generation vaccines for influenza.

A gene-based avian influenza vaccine in poultry

Highly pathogenic avian influenza A (HPAI) viruses, specifically H5N1 strains, cause widespread morbidity and mortality in domestic and wild bird populations, and recent outbreaks have resulted in severe economic losses. Although still largely confined to birds, more than 300 human cases resulting in deaths have been reported to the World Health Organization. These sporadic human cases result from direct transmission from infected birds; however, a sustained outbreak of HPAI H5N1 increases the potential for the emergence of a human pandemic strain. One approach to the containment of HPAI H5N1 is the development of vaccines for use in poultry. Currently, the majority of avian influenza vaccines for poultry are traditional whole-virus vaccines produced in eggs. Although highly efficacious, these vaccines are hindered by long production times, inflexibility in quickly altering antigenic composition, and limited breadth of protection. Newer vaccines with more efficient manufacturing processes, enhanced efficacy, and cross-protection against multiple strains would improve preparedness. Reverse genetics technology has provided one such method, and emerging gene-based vaccines offer another approach that reduces dependence on egg-based production and human exposure to pathogenic viruses. Gene-based vaccines also provide rapid manufacturing, enhanced precision and versatility, and the capacity to protect against a broad range of viral subtypes. Vectors for these vaccines include replication-defective viruses, bacterial vectors, and DNA. Here we review the features of gene-based vaccination that may facilitate the control of HPAI H5N1 in poultry, and highlight the development of a hemagglutinin-based multivalent DNA vaccine that confers protection in mice and chickens.

Clinical data on Fluarix: an inactivated split seasonal influenza vaccine

Influenza viruses cause annual winter epidemics in temperate regions, with significant morbidity, mortality and economical impact. Fluarix is a split, trivalent, inactivated vaccine, manufactured from highly purified, egg-grown influenza viruses by GlaxoSmithKline. In 2005, Fluarix underwent accelerated approval for use in adults by the US FDA following a US-based, randomized, placebo-controlled trial that established its safety and immunogenicity in adults. The vaccine has been licensed in Europe since 1992 for all age groups. Multiple registration trials in all age groups in Europe have demonstrated that the vaccine was safe and well tolerated and of immunogenicity standards that met the requirements of the European Committee for Medicinal Products for Human Use. There are no published clinical trials evaluating the effectiveness or efficacy of Fluarix against influenza and its complications. Currently, Fluarix plays an important role in the diversification of the supply chain of influenza vaccine to the community. However, vaccines with improved immunogenicity in at-risk populations, such as the elderly, and with less reliance on growth in eggs, as well as the inherent demanding timelines, are needed to enhance the control of influenza.

Pandemic and seasonal influenza: therapeutic challenges

Influenza A viruses cause significant morbidity and mortality annually, and the threat of a pandemic underscores the need for new therapeutic strategies. Here, we briefly discuss novel antiviral agents under investigation, the limitations of current antiviral therapy and stress the importance of secondary bacterial infections in seasonal and pandemic influenza. Additionally, the lack of new antibiotics available to treat increasingly drug resistant organisms such as methicillin-resistant Staphylococcus aureus, pneumococci, Acinetobacter, extended spectrum beta-lactamase producing gram negative bacteria and Clostridium difficile is highlighted as an important component of influenza treatment and pandemic preparedness. Addressing these problems will require a multidisciplinary approach, which includes the development of novel antivirals and new antibiotics, as well as a better understanding of the role secondary infections play on the morbidity and mortality of influenza infection.