Effectiveness of live, attenuated intranasal influenza virus vaccine in healthy, working adults: a randomized controlled trial

Duration of Virus Shedding After Trivalent Intranasal Live Attenuated Influenza Vaccination in Adults

Objective:

To characterize the probability and duration of viral shedding among adults given trivalent live attenuated influenza vaccine (LATV).

Design:

Prospective surveillance study.

Methods:

Nasal wash samples were collected from adult volunteers at baseline and on days 3, 7, and 10 and between days 17 and 21 following intranasal LAIV vaccination. The presence, titer, and identification of each specific strain of influenza virus shed were determined by standard methodology.

Results:

Twenty subjects received LATV. No samples were positive for influenza virus at baseline. After LAIV vaccination, influenza virus was recovered from 10 of 20 vaccinees on day 3, from 1 of 18 vaccinees on day 7, and from none of the samples on days 10 or 17 through 21. Vaccinees who shed vaccine virus were significantly younger than those who did not (mean age, 26.4 vs 38.6 years;P< .01). Although the presence of specific mucosal immunoglobulin A to influenza B was associated with significantly less shedding of influenza B after vaccination (P= .02), associations of shedding with other measures of immunity were not detected.

Conclusion:

The duration of shedding of vaccine virus after LAIV in adults is limited and may be associated with an individual's prior influenza vaccination history.

Antimicrobial therapy in childhood asthma and wheezing

There is an increasing number of viral and bacterial pathogens suspected of contributing to asthma pathogenesis in childhood, making it more difficult for the practitioner to make specific therapy decisions. This review discusses the role of viruses, e.g. respiratory syncytial virus, human metapneumovirus, influenza viruses and rhinoviruses, as well as the role of the atypical bacteria Chlamydophila pneumoniae and Mycoplasma pneumoniae, as contributors to childhood asthma. Diagnosis, prevention, and therapy are discussed, including a summary of drugs, i.e. macrolide antibacterials, antivirals, and vaccine regimens already available, or at least in clinical trials. For the practitioner dealing with patients every day, drug regimens are assigned to the individual pathogens and an algorithm for the management of atypical infections in patients with asthma or recurrent wheezing is presented.

Uptake and impact of vaccinating school age children against influenza during a season with circulation of drifted influenza A and B strains, England, 2014/15

The 2014/15 influenza season was the second season of roll-out of a live attenuated influenza vaccine (LAIV) programme for healthy children in England. During this season, besides offering LAIV to all two to four year olds, several areas piloted vaccination of primary (4-11 years) and secondary (11-13 years) age children. Influenza A(H3N2) circulated, with strains genetically and antigenically distinct from the 2014/15 A(H3N2) vaccine strain, followed by a drifted B strain. We assessed the overall and indirect impact of vaccinating school age children, comparing cumulative disease incidence in targeted and non-targeted age groups in vaccine pilot to non-pilot areas. Uptake levels were 56.8% and 49.8% in primary and secondary school pilot areas respectively. In primary school age pilot areas, cumulative primary care influenza-like consultation, emergency department respiratory attendance, respiratory swab positivity, hospitalisation and excess respiratory mortality were consistently lower in targeted and non-targeted age groups, though less for adults and more severe end-points, compared with non-pilot areas. There was no significant reduction for excess all-cause mortality. Little impact was seen in secondary school age pilot only areas compared with non-pilot areas. Vaccination of healthy primary school age children resulted in population-level impact despite circulation of drifted A and B influenza strains.

Vaccine Hesitancy

Vaccine refusal received a lot of press with the 2015 Disneyland measles outbreak, but vaccine refusal is only a fraction of a much larger problem of vaccine delay and hesitancy. Opposition to vaccination dates back to the 1800 s, Edward Jenner, and the first vaccine ever. It has never gone away despite the public's growing scientific sophistication. A variety of factors contribute to modern vaccine hesitancy, including the layperson's heuristic thinking when it comes to balancing risks and benefits as well as a number of other features of vaccination, including falling victim to its own success. Vaccine hesitancy is pervasive, affecting a quarter to a third of US parents. Clinicians report that they routinely receive requests to delay vaccines and that they routinely acquiesce. Vaccine rates vary by state and locale and by specific vaccine, and vaccine hesitancy results in personal risk and in the failure to achieve or sustain herd immunity to protect others who have contraindications to the vaccine or fail to generate immunity to the vaccine. Clinicians should adopt a variety of practices to combat vaccine hesitancy, including a variety of population health management approaches that go beyond the usual call to educate patients, clinicians, and the public. Strategies include using every visit to vaccinate, the creation of standing orders or nursing protocols to provide vaccination without clinical encounters, and adopting the practice of stating clear recommendations. Up-to-date, trusted resources exist to support clinicians' efforts in adopting these approaches to reduce vaccine hesitancy and its impact.

Effectiveness of seasonal influenza vaccine in preventing laboratory-confirmed influenza in primary care in the United Kingdom: 2014/15 end of season results

The 2014/15 influenza season in the United Kingdom (UK) was characterised by circulation of predominantly antigenically and genetically drifted influenza A(H3N2) and B viruses. A universal paediatric influenza vaccination programme using a quadrivalent live attenuated influenza vaccine (LAIV) has recently been introduced in the UK. This study aims to measure the end-of-season influenza vaccine effectiveness (VE), including for LAIV, using the test negative case–control design. The overall adjusted VE against all influenza was 34.3% (95% confidence interval (CI) 17.8 to 47.5); for A(H3N2) 29.3% (95% CI: 8.6 to 45.3) and for B 46.3% (95% CI: 13.9 to 66.5). For those aged under 18 years, influenza A(H3N2) LAIV VE was 35% (95% CI: −29.9 to 67.5), whereas for influenza B the LAIV VE was 100% (95% CI:17.0 to 100.0). Although the VE against influenza A(H3N2) infection was low, there was still evidence of significant protection, together with moderate, significant protection against drifted circulating influenza B viruses. LAIV provided non-significant positive protection against influenza A, with significant protection against B. Further work to assess the population impact of the vaccine programme across the UK is underway.

In Silico Identification of Highly Conserved Epitopes of Influenza A H1N1, H2N2, H3N2, and H5N1 with Diagnostic and Vaccination Potential

The unpredictable, evolutionary nature of the influenza A virus (IAV) is the primary problem when generating a vaccine and when designing diagnostic strategies; thus, it is necessary to determine the constant regions in viral proteins. In this study, we completed an in silico analysis of the reported epitopes of the 4 IAV proteins that are antigenically most significant (HA, NA, NP, and M2) in the 3 strains with the greatest world circulation in the last century (H1N1, H2N2, and H3N2) and in one of the main aviary subtypes responsible for zoonosis (H5N1). For this purpose, the HMMER program was used to align 3,016 epitopes reported in the Immune Epitope Database and Analysis Resource (IEDB) and distributed in 34,294 stored sequences in the Pfam database. Eighteen epitopes were identified: 8 in HA, 5 in NA, 3 in NP, and 2 in M2. These epitopes have remained constant since they were first identified (~91 years) and are present in strains that have circulated on 5 continents. These sites could be targets for vaccination design strategies based on epitopes and/or as markers in the implementation of diagnostic techniques.

Mucosally administered Lactobacillus surface-displayed influenza antigens (sM2 and HA2) with cholera toxin subunit A1 (CTA1) Induce broadly protective immune responses against divergent influenza subtypes

The development of a universal influenza vaccine that provides broad cross protection against existing and unforeseen influenza viruses is a critical challenge. In this study, we constructed and expressed conserved sM2 and HA2 influenza antigens with cholera toxin subunit A1 (CTA1) on the surface of Lactobacillus casei (pgsA-CTA1sM2HA2/L. casei). Oral and nasal administrations of recombinant L. casei into mice resulted in high levels of serum immunoglobulin G (IgG) and their isotypes (IgG1 & IgG2a) as well as mucosal IgA. The mucosal administration of pgsA-CTA1sM2HA2/L. casei may also significantly increase the levels of sM2- or HA2-specific cell-mediated immunity because increased release of both IFN-γ and IL-4 was observed. The recombinant pgsA-CTA1sM2HA2/L. casei provided better protection of BALB/c mice against 10 times the 50% mouse lethal doses (MLD50) of homologous A/EM/Korea/W149/06(H5N1) or A/Aquatic bird/Korea/W81/2005 (H5N2) and heterologous A/Puerto Rico/8/34(H1N1), or A/Chicken/Korea/116/2004(H9N2) or A/Philippines/2/08(H3N2) viruses, compared with L. casei harboring sM2HA2 and also the protection was maintained up to seven months after administration. These results indicate that recombinant L. casei expressing the highly conserved sM2, HA2 of influenza and CTA1 as a mucosal adjuvant could be a potential mucosal vaccine candidate or tool to protect against divergent influenza viruses for human and animal.

Vaccination in elite athletes

Public health vaccination guidelines cannot be easily transferred to elite athletes. An enhanced benefit from preventing even mild diseases is obvious but stronger interference from otherwise minor side effects has to be considered as well. Thus, special vaccination guidelines for adult elite athletes are required. In most of them, protection should be strived for against tetanus, diphtheria, pertussis, influenza, hepatitis A, hepatitis B, measles, mumps and varicella. When living or traveling to endemic areas, the athletes should be immune against tick-borne encephalitis, yellow fever, Japanese encephalitis, poliomyelitis, typhoid fever, and meningococcal disease. Vaccination against pneumococci and Haemophilus influenzae type b is only relevant in athletes with certain underlying disorders. Rubella and papillomavirus vaccination might be considered after an individual risk–benefit analysis. Other vaccinations such as cholera, rabies, herpes zoster, and Bacille Calmette–Guérin (BCG) cannot be universally recommended for athletes at present. Only for a very few diseases, a determination of antibody titers is reasonable to avoid unnecessary vaccinations or to control efficacy of an individual’s vaccination (especially for measles, mumps, rubella, varicella, hepatitis B and, partly, hepatitis A). Vaccinations should be scheduled in a way that possible side effects are least likely to occur in periods of competition. Typically, vaccinations are well tolerated by elite athletes, and resulting antibody titers are not different from the general population. Side effects might be reduced by an optimal selection of vaccines and an appropriate technique of administration. Very few discipline-specific considerations apply to an athlete’s vaccination schedule mainly from the competition and training pattern as well as from the typical geographical distribution of competitive sites.

Influenza vaccines for preventing cardiovascular disease

BACKGROUND

This is an update of the original review published in 2008. The risk of adverse cardiovascular outcomes is increased with influenza-like infection, and vaccination against influenza may improve cardiovascular outcomes.

OBJECTIVES

To assess the potential benefits of influenza vaccination for primary and secondary prevention of cardiovascular disease.

SEARCH METHODS

We searched the following electronic databases on 18 October 2013: The Cochrane Library (including Cochrane Central Register of Controlled Trials (CENTRAL), Database of Abstracts of Reviews of Effects (DARE), Economic Evaluation Database (EED) and Health Technology Assessment database (HTA)), MEDLINE, EMBASE, Science Citation Index Expanded, Conference Proceedings Citation Index - Science and ongoing trials registers (www.controlled-trials.com/ and www.clinicaltrials.gov). We examined reference lists of relevant primary studies and systematic reviews. We performed a limited PubMed search on 20 February 2015, just before publication.

SELECTION CRITERIA

Randomised controlled trials (RCTs) of influenza vaccination compared with placebo or no treatment in participants with or without cardiovascular disease, assessing cardiovascular death or non-fatal cardiovascular events.

DATA COLLECTION AND ANALYSIS

We used standard methodological procedures as expected by The Cochrane Collaboration. We carried out meta-analyses only for cardiovascular death, as other outcomes were reported too infrequently. We expressed effect sizes as risk ratios (RRs), and we used random-effects models.

MAIN RESULTS

We included eight trials of influenza vaccination compared with placebo or no vaccination, with 12,029 participants receiving at least one vaccination or control treatment. We included six new studies (n = 11,251), in addition to the two included in the previous version of the review. Four of these trials (n = 10,347) focused on prevention of influenza in the general or elderly population and reported cardiovascular outcomes among their safety analyses; four trials (n = 1682) focused on prevention of cardiovascular events in patients with established coronary heart disease. These populations were analysed separately. Follow-up continued between 42 days and one year. Five RCTs showed deficits in at least three of the risk of bias criteria assessed. When reported (seven studies), vaccination provided adequate immunogenicity or protection against influenza. Cardiovascular mortality was reported by four secondary prevention trials and was significantly reduced by influenza vaccination overall (risk ratio (RR) 0.45, 95% confidence interval (CI) 0.26 to 0.76; P value 0.003) with no significant heterogeneity between studies, and by three trials reporting cardiovascular mortality as part of their safety analyses when the numbers of events were too small to permit conclusions. In studies of patients with coronary heart disease, composite outcomes of cardiovascular events tended to be decreased with influenza vaccination compared with placebo. Generally no significant difference was found between comparison groups regarding individual outcomes such as myocardial infarction.

AUTHORS' CONCLUSIONS

In patients with cardiovascular disease, influenza vaccination may reduce cardiovascular mortality and combined cardiovascular events. However, studies had some risk of bias, and results were not always consistent, so additional higher-quality evidence is necessary to confirm these findings. Not enough evidence was available to establish whether influenza vaccination has a role to play in the primary prevention of cardiovascular disease.

Influenza Vaccination Strategies: Comparing Inactivated and Live Attenuated Influenza Vaccines

Influenza is a major respiratory pathogen causing annual outbreaks and occasional pandemics. Influenza vaccination is the major method of prophylaxis. Currently annual influenza vaccination is recommended for groups at high risk of complications from influenza infection such as pregnant women, young children, people with underlying disease and the elderly, along with occupational groups such a healthcare workers and farm workers. There are two main types of vaccines available: the parenteral inactivated influenza vaccine and the intranasal live attenuated influenza vaccine. The inactivated vaccines are licensed from 6 months of age and have been used for more than 50 years with a good safety profile. Inactivated vaccines are standardized according to the presence of the viral major surface glycoprotein hemagglutinin and protection is mediated by the induction of vaccine strain specific antibody responses. In contrast, the live attenuated vaccines are licensed in Europe for children from 2-17 years of age and provide a multifaceted immune response with local and systemic antibody and T cell responses but with no clear correlate of protection. Here we discuss the immunological immune responses elicited by the two vaccines and discuss future work to better define correlates of protection.

Influenza Vaccination Rates and Motivators Among Healthcare Worker Groups

Background.

The rate of influenza vaccination among healthcare workers (HCWs) is approximately 40%. Differences in vaccination rates among HCW groups and reasons for accepting or rejecting vaccination are poorly understood.

Objectives.

To determine vaccination rates and motivators among different HCW groups during the 2004-2005 influenza season.

Design.

Cross-sectional survey conducted between July 10 and September 30, 2005.

Setting.

Two tertiary care teaching hospitals in an urban center.

Participants.

Physicians, nurses, nursing aides, and other staff. Surveys were collected from 1,042 HCWs (response rate, 42%).

Results.

Sixty-nine percent of physicians (n = 282) and 63% of medical students (n = 145) were vaccinated, compared with 46% of nurses (n = 336), 42% of nursing aides (n = 135), and 29% of administrative personnel (n = 144). Physicians and medical students were significantly more likely to be vaccinated than all other groups (P < .0001). Pediatricians (84%) were more likely than internists (69%) and surgeons (43%) to be vaccinated (P < .0001). Among the HCWs who were vaccinated, 33.4% received the live attenuated influenza vaccine (LAIV) and 66.6% received trivalent inactivated influenza vaccine (TIV). Vaccinated HCWs were less likely than unvaccinated HCWs to report an influenza-like illness (P = .03). Vaccination with LAIV resulted in fewer episodes of influenza-like illness than did receiving no vaccine (P = .03). The most common reason for rejecting vaccination was a concern about availability. Understanding that HCWs may transmit the virus to patients correlated with vaccine acceptance (P = .0004).

Conclusions.

Significant differences in vaccination exist among physician specialties and employee groups, and there are inadequate vaccination rates among those with the greatest amount of patient contact, potentially providing a basis for group-specific interventions.

Intranasal seasonal influenza vaccine and a TLR-3 agonist, rintatolimod, induced cross-reactive IgA antibody formation against avian H5N1 and H7N9 influenza HA in humans

The intranasal use of rintatolimod, a specific TLR-3 agonist, combined with trivalent seasonal influenza vaccine generated cross-protection against highly pathogenic H5N1 avian influenza in mice. The purpose of this clinical trial is to assess the safety and impact of rintatolimod on intranasal influenza vaccine in healthy adults. During Stage I of this Phase I/II clinical trial, 12 volunteers were immunized intranasally with 3 doses of FluMist seasonal influenza vaccine on Days 0, 28, and 56 followed by intranasal rintatolimod (50 μg, 200 μg, or 500 μg) 3 days later. Parotid saliva and nasal wash samples were collected at baseline and on Days 25, 53, 84, and 417. The samples were tested for IgA and IgG specific antibodies (Ab) directed against the homologous FluMist viral hemagglutinins (HAs). In addition, viral specific responses against influenza A HAs were tested for IgA Ab cross-reactivity against 3 H5 clades: HA (H5N1) A/Indonesia/5/2005, HA (H5N1) A/Hong Kong/483/97 and HA (H5N1) A/Vietnam/1194/2004, as well as, two H7 strains, HA (H7N9) A/Shanghai/2/2013 and HA (H7N3) A/chicken/Jalisco/CPA1. The combination of the intranasal FluMist along with the rintatolimod generated specific secretory IgA responses of at least 4-fold over baseline against at least one of the homologous vaccine strains included in the vaccine in 92% of the vaccinees. Additionally, this vaccination strategy induced cross-reactive secretory IgA against highly pathogenic avian influenza virus strains H5N1, H7N9, and H7N3 with pandemic potential for humans. The combination of rintatolimod and FluMist was well-tolerated.

Considerations for the rapid deployment of vaccines against H7N9 influenza

The threat of an outbreak of avian-origin influenza H7N9 and the devastating consequences that a pandemic could have on global population health and economies has mobilized programs of constant surveillance and the implementation of preemptive plans. Central to these plans is the production of prepandemic vaccines that can be rapidly deployed to minimize disease severity and deaths resulting from such an occurrence. In this article, we review current H7N9 vaccine strategies in place and the available technologies and options that can help accelerate vaccine production and increase dose-sparing capabilities to provide enough vaccines to cover the population. We also present possible means of reducing disease impact during the critical period after an outbreak occurs before a strain matched vaccine becomes available and consider the use of existing stockpiles and seed strains of phylogenetically related subtypes, alternate vaccination regimes and vaccine forms that induce cross-reactive immunity.

Development of live attenuated influenza vaccines against pandemic influenza strains

Avian and animal influenza viruses can sporadically transmit to humans, causing outbreaks of varying severity. In some cases, further human-to-human virus transmission does not occur, and the outbreak in humans is limited. In other cases, sustained human-to-human transmission occurs, resulting in worldwide influenza pandemics. Preparation for future pandemics is an important global public health goal. A key objective of preparedness is to gain an understanding of how to design, test, and manufacture effective vaccines that could be stockpiled for use in a pandemic. This review summarizes results of an ongoing collaboration to produce, characterize, and clinically test a library of live attenuated influenza vaccine strains (based on Ann Arbor attenuated Type A strain) containing protective antigens from influenza viruses considered to be of high pandemic potential.

Antimicrobial stewardship in daily practice: Managing an important resource

Antimicrobial stewardship is a recent concept that embodies the practical, judicious use of antimicrobials to decrease adverse outcomes from antimicrobials while optimizing the treatment of bacterial infections to reduce the emergence of resistant pathogens. The objectives of the present statement are to illustrate the principles of antimicrobial stewardship and to offer practical examples of how to make antimicrobial stewardship part of everyday hospital and outpatient practice. Vital components of antimicrobial stewardship include appropriate testing to diagnose whether infections are viral or bacterial, and using clinical follow-up rather than antibiotics in cases in which the child is not very ill and uncertainty exists. Other specific, important actions include questioning whether positive urine cultures are contaminated when there is no evidence of pyuria or inflammatory changes, and obtaining a chest radiograph to support a diagnosis of bacterial pneumonia. Optimizing the choice and dosage of antimicrobials also reduces the probability of clinical failures and subsequent courses of antimicrobials. A list of common clinical scenarios to promote stew-ardship is included.

Distinct cross-reactive B-cell responses to live attenuated and inactivated influenza vaccines

BACKGROUND

The immunological bases for the efficacies of the 2 currently licensed influenza vaccines, live attenuated influenza vaccine (LAIV) and inactivated influenza vaccine (IIV), are not fully understood. The goal of this study was to identify specific B-cell responses correlated with the known efficacies of these 2 vaccines.

METHODS

We compared the B-cell and antibody responses after immunization with 2010/2011 IIV or LAIV in young adults, focusing on peripheral plasmablasts 6-8 days after vaccination.

RESULTS

The quantities of vaccine-specific plasmablasts and plasmablast-derived polyclonal antibodies (PPAbs) in IIV recipients were significantly higher than those in LAIV recipients. No significant difference was detected in the avidity of vaccine-specific PPAbs between the 2 vaccine groups. Proportionally, LAIV induced a greater vaccine-specific immunoglobulin A plasmablast response, as well as a greater plasmablast response to the conserved influenza nuclear protein, than IIV. The cross-reactive plasmablast response to heterovariant strains, as indicated by the relative levels of cross-reactive plasmablasts and the cross-reactive PPAb binding reactivity, was also greater in the LAIV group.

CONCLUSIONS

Distinct quantitative and qualitative patterns of plasmablast responses were induced by LAIV and IIV in young adults; a proportionally greater cross-reactive response was induced by LAIV.

Vaccines for preventing influenza in healthy adults

BACKGROUND

Different types of influenza vaccines are currently produced worldwide. Vaccination of pregnant women is recommended internationally, while healthy adults are targeted in North America.

OBJECTIVES

To identify, retrieve and assess all studies evaluating the effects (efficacy, effectiveness and harm) of vaccines against influenza in healthy adults, including pregnant women.

SEARCH METHODS

We searched the Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library 2013, Issue 2), MEDLINE (January 1966 to May 2013) and EMBASE (1990 to May 2013).

SELECTION CRITERIA

Randomised controlled trials (RCTs) or quasi-RCTs comparing influenza vaccines with placebo or no intervention in naturally occurring influenza in healthy individuals aged 16 to 65 years. We also included comparative studies assessing serious and rare harms.

DATA COLLECTION AND ANALYSIS

Two review authors independently assessed trial quality and extracted data.

MAIN RESULTS

We included 90 reports containing 116 data sets; among these 69 were clinical trials of over 70,000 people, 27 were comparative cohort studies (about eight million people) and 20 were case-control studies (nearly 25,000 people). We retrieved 23 reports of the effectiveness and safety of vaccine administration in pregnant women (about 1.6 million mother-child couples).The overall effectiveness of parenteral inactivated vaccine against influenza-like illness (ILI) is limited, corresponding to a number needed to vaccinate (NNV) of 40 (95% confidence interval (CI) 26 to 128). The overall efficacy of inactivated vaccines in preventing confirmed influenza has a NNV of 71 (95% CI 64 to 80). The difference between these two values depends on the different incidence of ILI and confirmed influenza among the study populations: 15.6% of unvaccinated participants versus 9.9% of vaccinated participants developed ILI symptoms, whilst only 2.4% and 1.1%, respectively, developed laboratory-confirmed influenza.No RCTs assessing vaccination in pregnant women were found. The only evidence available comes from observational studies with modest methodological quality. On this basis, vaccination shows very limited effects: NNV 92 (95% CI 63 to 201) against ILI in pregnant women and NNV 27 (95% CI 18 to 185) against laboratory-confirmed influenza in newborns from vaccinated women.Live aerosol vaccines have an overall effectiveness corresponding to a NNV 46 (95% CI 29 to 115).The performance of one-dose or two-dose whole virion pandemic vaccines was higher, showing a NNV of 16 (95% CI 14 to 20) against ILI and a NNV of 35 (95% CI 33 to 47) against influenza, while a limited impact on hospitalisation was found (NNV 94, 95% CI 70 to 1022).Vaccination had a modest effect on time off work and had no effect on hospital admissions or complication rates. Inactivated vaccines caused local harms. No evidence of association with serious adverse events was found, but the harms evidence base was limited.The overall risk of bias in the included trials is unclear because it was not possible to assess the real impact of bias.

AUTHORS' CONCLUSIONS

Influenza vaccines have a very modest effect in reducing influenza symptoms and working days lost in the general population, including pregnant women. No evidence of association between influenza vaccination and serious adverse events was found in the comparative studies considered in the review. This review includes 90 studies, 24 of which (26.7%) were funded totally or partially by industry. Out of the 48 RCTs, 17 were industry-funded (35.4%).

Cold-adapted, live attenuated influenza vaccine

The recently licensed cold-adapted, live attenuated influenza vaccine (CAIV-T, FluMist, MedImmune Vaccines Inc.) has the potential to enhance control of epidemic influenza. The intranasal vaccine has proven safety and efficacy. Regulatory constraints and cost of CAIV-T have hampered the introduction of the vaccine in the first year. Unwarranted concern about possible transmission of the virus from vaccine recipients to immunocompromised patients limited use in healthcare personnel. The intense influenza A(H3N2) epidemic of 2003-2004 has underscored the necessity of supplementing current efforts to control influenza. Over 120 deaths have been documented in children - the majority of which have been previously healthy. Use of CAIV-T in children will not only decrease the risk of serious disease, but also dampen the spread of the virus in the community and reduce exposure of patients who are at high risk of complications and death.

Prevention and Control of Influenza Viruses

The 2003–2004 outbreaks of highly pathogenic avian influenza (HPAI) have proven to be disastrous to the regional poultry industry in Asia, and have raised serious worldwide public health apprehension regarding the steps that should be taken to urgently control HPAI. Control measures must be taken based on the principles of biosecurity and disease management and at the same time making public aware of the precautionary measures at the verge of outbreak. Creation of protection and surveillance zones, various vaccination strategies viz. routine, preventive, emergency, mass and targeted vaccination programmes using live, inactivated and recombinant vaccines are the common strategies adopted in different parts of the globe. The new generation vaccines include recombinant vaccines and recombinant fusion vaccine. The pro-poor disease control programmes, giving compensation and subsidies to the farmers along with effective and efficient Veterinary Services forms integral part of control of HPAI. Following biosecurity principles and vaccination forms integral part of control programme against swine and equine influenza as well. Use of neuraminidase (NA) inhibitors (Zanamivir and Oseltamivir) for the treatment of human influenza has been widely accepted worldwide. The threat of increasing resistance of the flu viruses to these antivirals has evoked interest in the development of novel antiviral drugs for influenza virus such as inhibitors of cellular factors and host signalling cascades, cellular miRNAs, siRNA and innate immune peptides (defensins and cathelicidins). Commercial licensed inactivated vaccines for humans against influenza A and B viruses are available consisting of three influenza viruses: influenza type A subtype H3N2, influenza type A subtype H1N1 (seasonal) virus strain and influenza type B virus strain. As per WHO, use of tetravaccine consisting of antigens of influenza virus serotypes H3N2, H1N1, B and H5 is the most promising method to control influenza pandemic. All healthy children in many countries are required to be vaccinated between 6 and 59 months of age. The seasonal vaccines currently used in humans induce strain-specific humoral immunity as the antibodies. Universal influenza virus vaccines containing the relatively conserved ectodomain of M2 (M2e), M1, HA fusion peptide and stalk domains, NA, NP alone or in combination have been developed which have been shown to induce cross-protection. The T cell-based vaccines are another recent experimental approach that has been shown to elicit broad-spectrum heterosubtypic immunity in the host. As far as HPAI is concerned, various pandemic preparedness strategies have been documented.

Alveolar macrophages contribute to respiratory tolerance by inducing FoxP3 expression in naive T cells

Alveolar macrophages (AMs) from mice and humans have long been known to contribute to maintaining tolerance in the lung. Studies have shown that AMs can induce anergy in CD4(+) T cells. Nitric oxide, prostaglandins, and leukotrienes have been implicated in AM-mediated tolerance. However, it remains unclear what effect, if any, AMs exert on FoxP3 induction in CD4(+) T cells from mice and humans, and whether or not other immunomodulators might play a role. AMs were isolated from bronchoalveolar lavage (BAL) fluid from either mice or humans, and cocultured with enriched naive CD4(+)FoxP3(-) T cells. We show here for the first time that AMs and AM-conditioned media (AM-CM) from mice and humans induced FoxP3 expression in naive CD4(+) T cells in vitro, an outcome that was reversed in part either by inhibiting retinoic acid (RA) binding to its receptor (RAR), or by blocking transforming growth factor (TGF)-β₁ signaling. A nasal administration of the RAR antagonist reduced the frequencies of CD4(+)FoxP3(+) T cells in the lungs of mice after aerosol challenge with Bordetella pertussis. In addition, we found that the intranasal vaccination of mice with ovalbumin (OVA) protein in conjunction with an RAR inhibitor led to a significant increase in OVA-specific serum IgE. Our findings suggest that AMs can mediate tolerance in the lungs of mice and humans via RA and TGF-β₁. These data may have implications in the development of nasal vaccines in the future.

Live attenuated tularemia vaccines: recent developments and future goals

In the aftermath of the 2001 anthrax attacks in the U.S., numerous efforts were made to increase the level of preparedness against a biological attack both in the US and worldwide. As a result, there has been an increase in research interest in the development of vaccines and other countermeasures against a number of agents with the potential to be used as biological weapons. One such agent, Francisella tularensis, has been the subject of a surge in the level of research being performed, leading to a substantial increase in knowledge of the pathogenic mechanisms of the organism and the induced immune responses. This information has facilitated the development of multiple new Francisella vaccine candidates. Herein we review the latest live attenuated F. tularensis vaccine efforts. Historically, live attenuated vaccines have demonstrated the greatest degree of success in protection against tularemia and the greatest promise in recent efforts to develop of a fully protective vaccine. This review summarizes recent live attenuated Francisella vaccine candidates and the lessons learned from those studies, with the goal of collating known characteristics associated with successful attenuation, immunogenicity, and protection.

Self-Immunization with Live Attenuated Influenza Vaccine in a Mass Vaccination Clinic

Objective

An influenza pandemic may demand that a large number of influenza immunizations be rapidly given with limited resources. This study tested the utility and practicality of self-immunization with live attenuated influenza intranasal vaccine in a mass vaccination event.

Methods

The self-immunization clinic model was evaluated in a three-tiered fashion using student, first responder, and open community events.

Results

A single nurse was easily able to direct 89 people through the process of self-administration of the vaccine in a three-hour first-responder event and 122 people in a three-hour open community event. 96% of participants believed that they had performed the self-administration correctly, and the same percentage reported that they would like to receive influenza immunization by self-vaccination in the future.

Conclusions

The self-immunization clinic is a practical and potentially useful model in an influenza pandemic setting.

Cross-protective immune responses elicited by live attenuated influenza vaccines

The desired effect of vaccination is to elicit protective immune responses against infection with pathogenic agents. An inactivated influenza vaccine is able to induce the neutralizing antibodies directed primarily against two surface antigens, hemagglutinin and neuraminidase. These two antigens undergo frequent antigenic drift and hence necessitate the annual update of a new vaccine strain. Besides the antigenic drift, the unpredictable emergence of the pandemic influenza strain, as seen in the 2009 pandemic H1N1, underscores the development of a new influenza vaccine that elicits broadly protective immunity against the diverse influenza strains. Cold-adapted live attenuated influenza vaccines (CAIVs) are advocated as a more appropriate strategy for cross-protection than inactivated vaccines and extensive studies have been conducted to address the issues in animal models. Here, we briefly describe experimental and clinical evidence for cross-protection by the CAIVs against antigenically distant strains and discuss possible explanations for cross-protective immune responses afforded by CAIVs. Potential barriers to the achievement of a universal influenza vaccine are also discussed, which will provide useful guidelines for future research on designing an ideal influenza vaccine with broad protection without causing pathogenic effects such as autoimmunity or attrition of protective immunity against homologous infection.

Nasal drug delivery devices: characteristics and performance in a clinical perspective-a review

Nasal delivery is the logical choice for topical treatment of local diseases in the nose and paranasal sinuses such as allergic and non-allergic rhinitis and sinusitis. The nose is also considered an attractive route for needle-free vaccination and for systemic drug delivery, especially when rapid absorption and effect are desired. In addition, nasal delivery may help address issues related to poor bioavailability, slow absorption, drug degradation, and adverse events in the gastrointestinal tract and avoids the first-pass metabolism in the liver. However, when considering nasal delivery devices and mechanisms, it is important to keep in mind that the prime purpose of the nasal airway is to protect the delicate lungs from hazardous exposures, not to serve as a delivery route for drugs and vaccines. The narrow nasal valve and the complex convoluted nasal geometry with its dynamic cyclic physiological changes provide efficient filtration and conditioning of the inspired air, enhance olfaction, and optimize gas exchange and fluid retention during exhalation. However, the potential hurdles these functional features impose on efficient nasal drug delivery are often ignored. With this background, the advantages and limitations of existing and emerging nasal delivery devices and dispersion technologies are reviewed with focus on their clinical performance. The role and limitations of the in vitro testing in the FDA guidance for nasal spray pumps and pressurized aerosols (pressurized metered-dose inhalers) with local action are discussed. Moreover, the predictive value and clinical utility of nasal cast studies and computer simulations of nasal airflow and deposition with computer fluid dynamics software are briefly discussed. New and emerging delivery technologies and devices with emphasis on Bi-Directional™ delivery, a novel concept for nasal delivery that can be adapted to a variety of dispersion technologies, are described in more depth.

The safety and effectiveness of self-administration of intranasal live attenuated influenza vaccine in adults

Intranasal live attenuated influenza vaccine (LAIV) has potential for self-administration (SA) by adults and adolescents, which could save time and cost in mass vaccination settings. Participants in a study of LAIV in adults (n=4561) selected either SA or health care provider (HCP) administration and were followed for febrile illness during the influenza season. More LAIV recipients chose SA-LAIV (72%) than HCP-LAIV (28%). Overall, 97% of SA-LAIV and 98% of HCP-LAIV recipients had no problems with vaccine administration. Four of 13 study sites enrolled more than 50 subjects in both cohorts. Overall and for these 4 sites, illness incidence was similar with SA-LAIV and HCP-LAIV. Solicited reactogenicity events and adverse events through 7 days post vaccination were comparable for SA-LAIV and HCP-LAIV recipients; both groups exhibited increased runny nose, sore throat, and cough relative to placebo recipients. SA-LAIV and HCP-LAIV appeared similarly effective against influenza-like illness and had comparable safety profiles.

Comparative study of influenza virus replication in MDCK cells and in primary cells derived from adenoids and airway epithelium

Although clinical trials with human subjects are essential for determination of safety, infectivity, and immunogenicity, it is desirable to know in advance the infectiousness of potential candidate live attenuated influenza vaccine strains for human use. We compared the replication kinetics of wild-type and live attenuated influenza viruses, including H1N1, H3N2, H9N2, and B strains, in Madin-Darby canine kidney (MDCK) cells, primary epithelial cells derived from human adenoids, and human bronchial epithelium (NHBE cells). Our data showed that despite the fact that all tissue culture models lack a functional adaptive immune system, differentiated cultures of human epithelium exhibited the greatest restriction for all H1N1, H3N2, and B vaccine viruses studied among three cell types tested and the best correlation with their levels of attenuation seen in clinical trials with humans. In contrast, the data obtained with MDCK cells were the least predictive of restricted viral replication of live attenuated vaccine viruses in humans. We were able to detect a statistically significant difference between the replication abilities of the U.S. (A/Ann Arbor/6/60) and Russian (A/Leningrad/134/17/57) cold-adapted vaccine donor strains in NHBE cultures. Since live attenuated pandemic influenza vaccines may potentially express a hemagglutinin and neuraminidase from a non-human influenza virus, we assessed which of the three cell cultures could be used to optimally evaluate the infectivity and cellular tropism of viruses derived from different hosts. Among the three cell types tested, NHBE cultures most adequately reflected the infectivity and cellular tropism of influenza virus strains with different receptor specificities. NHBE cultures could be considered for use as a screening step for evaluating the restricted replication of influenza vaccine candidates.

Immunogenicity of a quadrivalent Ann Arbor strain live attenuated influenza vaccine delivered using a blow-fill-seal device in adults: a randomized, active-controlled study*

BACKGROUND

Influenza B strains from two distinct lineages (Yamagata and Victoria) have cocirculated over recent years. Current seasonal vaccines contain a single B lineage resulting in frequent mismatches between the vaccine strain and the circulating strain. An Ann Arbor strain quadrivalent live attenuated influenza vaccine (Q/LAIV) containing B strains from both lineages is being developed to address this issue.

OBJECTIVES

The goal of this study was to evaluate whether Q/LAIV administered intranasally as a single dose to a single nostril, using a blow-fill-seal (BFS) delivery system had a similar immunogenicity and safety profile compared with the licensed trivalent vaccine delivered using the Accuspray device.

PATIENTS/METHODS

Adults aged 18-49 years were randomized to receive one intranasal dose of Q/LAIV delivered using a BFS device (Q/LAIV-BFS; n=1202) or one of two trivalent live attenuated influenza vaccines (T/LAIV) containing one of the corresponding B strains (total T/LAIV, n=598). Primary endpoints were the post-vaccination strain-specific serum hemagglutination inhibition antibody geometric mean titers for each strain. Secondary immunogenicity endpoints, safety, and acceptability of the BFS device were also assessed.

RESULTS

Q/LAIV was immunogenically non-inferior to T/LAIV for all four influenza strains. Secondary immunogenicity outcomes were consistent with the primary endpoint. Solicited symptoms and AEs were comparable in both groups. Subjects considered the BFS device to be acceptable.

CONCLUSIONS

Immune responses to vaccination with Ann Arbor strain Q/LAIV-BFS were non-inferior to those with T/LAIV. Q/LAIV may confer broader protection against seasonal influenza B by targeting both major influenza B lineages.

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.

Immunity to the conserved influenza nucleoprotein reduces susceptibility to secondary bacterial infections

Influenza causes >250,000 deaths annually in the industrialized world, and bacterial infections frequently cause secondary illnesses during influenza outbreaks, including pneumonia, bronchitis, sinusitis, and otitis media. In this study, we demonstrate that cross-reactive immunity to mismatched influenza strains can reduce susceptibility to secondary bacterial infections, even though this fails to prevent influenza infection. Specifically, infecting mice with H3N2 influenza before challenging with mismatched H1N1 influenza reduces susceptibility to either Gram-positive Streptococcus pneumoniae or Gram-negative Klebsiella pneumoniae. Vaccinating mice with the highly conserved nucleoprotein of influenza also reduces H1N1-induced susceptibility to lethal bacterial infections. Both T cells and Abs contribute to defense against influenza-induced bacterial diseases; influenza cross-reactive T cells reduce viral titers, whereas Abs to nucleoprotein suppress induction of inflammation in the lung. These findings suggest that nonneutralizing influenza vaccines that fail to prevent influenza infection may nevertheless protect the public from secondary bacterial diseases when neutralizing vaccines are not available.

Immunomodulatory properties of subcellular fractions of a G+ bacterium, Bacillus firmus

Mucosal immunization with non-living antigens usually requires the use of an adjuvant. The adjuvant activity of Bacillus firmus in the mucosal immunization of mice was described by our laboratory previously. In the present study, subcellular localization of B. firmus activities was followed. After mechanical disintegration, subcellular components of bacterium were fractionated by differential centrifugation and salting out. Bacterial cell walls, cytoplasmic membrane fraction, soluble cytoplasmic proteins, and ribosomal fractions were isolated. Their effect on the mouse immune system was studied. Lymphocyte proliferation and immunoglobulin formation in vitro were stimulated by bacterial cell wall (BCW), cytoplasmic membrane (CMF), and ribosomal fractions. BCW and CMF increased antibody formation after intratracheal immunization of mice with influenza A and B viruses, and increased protection against subsequent infection with influenza virus. The BCW fraction even induced intersubtypic cross-protection: Mice immunized with A/California/7/04 (H3N2) + BCW were resistant to the infection by the highly pathogenic A/PR/8/34 (H1N1) virus.

An open-label phase I trial of a live attenuated H2N2 influenza virus vaccine in healthy adults

Please cite this paper as: Talaat et al. (2012) An open‐label phase I trial of a live attenuated H2N2 influenza virus vaccine in healthy adults. Influenza and Other Respiratory Viruses DOI: 10.1111/j.1750‐2659.2012.00350.x.

Background  Live attenuated influenza vaccines (LAIV) against a variety of strains of pandemic potential are being developed and tested. We describe the results of an open‐label phase I trial of a live attenuated H2N2 virus vaccine.

Objectives  To evaluate the safety, infectivity, and immunogenicity of a live attenuated H2N2 influenza virus vaccine.

Participants/methods  The A/Ann Arbor/6/60 (H2N2) virus used in this study is the attenuated, cold‐adapted, temperature‐sensitive strain that provides the genetic backbone of seasonal LAIV (MedImmune). We evaluated the safety, infectivity, and immunogenicity of two doses of 10⁷ TCID₅₀ of this vaccine administered by nasal spray 4 weeks apart to normal healthy seronegative adults.

Results  Twenty‐one participants received a first dose of the vaccine; 18 participants received a second dose. No serious adverse events occurred during the trial. The most common adverse events after vaccination were headache and musculoskeletal pain. The vaccine was restricted in replication: 24% and 17% had virus detectable by culture or rRT‐PCR after the first and second dose, respectively. Antibody responses to the vaccine were also restricted: 24% of participants developed an antibody response as measured by either hemagglutination‐inhibition assay (10%), or ELISA for H2 HA‐specific serum IgG (24%) or IgA (16%) after either one or two doses. None of the participants had a neutralizing antibody response. Vaccine‐specific IgG‐secreting cells as measured by enzyme‐linked immunospot increased from a mean of 0·5 to 2·0/10⁶ peripheral blood mononuclear cells (PBMCs); vaccine‐specific IgA‐secreting cells increased from 0·1 to 0·5/10⁶ PBMCs.

Conclusions  The live attenuated H2N2 1960 AA ca vaccine demonstrated a safety profile consistent with seasonal trivalent LAIV but was restricted in replication and minimally immunogenic in healthy seronegative adults.

A postmarketing evaluation of the safety of Ann Arbor strain live attenuated influenza vaccine in adults 18-49 years of age

BACKGROUND

The Ann Arbor strain-live attenuated influenza vaccine (LAIV) was licensed in 2003 for use in the United States for individuals aged 5-49 years of age. As part of a postmarketing commitment to safety, LAIV was studied in adults 18-49 years participating in the Kaiser Permanente Health Plan over 5 influenza seasons.

METHODS

Individuals received LAIV as part of routine care from October 2003 through March 2008. Using Kaiser Permanente databases, rates of medically attended events (MAEs) and serious adverse events (SAEs) in LAIV recipients were compared with rates in multiple non-randomized control groups which included a self-control group, matched unvaccinated controls, and matched controls vaccinated with inactivated influenza vaccine (TIV).

RESULTS

A total of 21,340, 18,316, and 21,340 subjects received LAIV, TIV and no vaccine, respectively. More than 5500 MAE incidence rate comparisons were performed, and of these, 257 (5%) yielded statistically significant differences with 72 and 185 occurring at a higher and lower rate after LAIV compared with control groups, respectively. The pattern of MAE rate differences did not suggest any safety signal associated with LAIV. There were 47 SAEs noted, and no individual SAE occurred at a significantly higher or lower rate in LAIV recipients relative to control groups in any comparison. Only 2 SAEs (migraine/sinusitis and Bell's palsy) were considered possibly or probably related to LAIV.

CONCLUSION

The results of this post-licensure evaluation of LAIV safety in individuals 18-49 years of age are consistent with pre- and post-approval clinical studies as well as reports to the U.S. Vaccine Adverse Events Reporting System, all of which demonstrated no significant adverse outcomes among eligible individuals following receipt of LAIV.

The contribution of systemic and pulmonary immune effectors to vaccine-induced protection from H5N1 influenza virus infection

Live attenuated influenza vaccines (LAIVs) are effective in providing protection against influenza challenge in animal models and in preventing disease in humans. We previously showed that LAIVs elicit a range of immune effectors and that successful induction of pulmonary cellular and humoral immunity in mice requires pulmonary replication of the vaccine virus. An upper respiratory tract immunization (URTI) model was developed in mice to mimic the human situation, in which the vaccine virus does not replicate in the lower respiratory tract, allowing us to assess the protective efficacy of an H5N1 LAIV against highly pathogenic H5N1 virus challenge in the absence of significant pulmonary immunity. Our results show that, after one dose of an H5N1 LAIV, pulmonary influenza-specific lymphocytes are the main contributors to clearance of challenge virus from the lungs and that contributions of influenza-specific enzyme-linked immunosorbent assay (ELISA) antibodies in serum and splenic CD8(+) T cells were negligible. Complete protection from H5N1 challenge was achieved after two doses of H5N1 LAIV and was associated with maturation of the antibody response. Although passive transfer of sera from mice that received two doses of vaccine prevented lethality in naive recipients following challenge, the mice showed significant weight loss, with high pulmonary titers of the H5N1 virus. These data highlight the importance of mucosal immunity in mediating optimal protection against H5N1 infection. Understanding the requirements for effective induction and establishment of these protective immune effectors in the respiratory tract paves the way for a more rational and effective vaccine approach in the future.

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.

Live attenuated influenza vaccine (FluMist®; Fluenz™): a review of its use in the prevention of seasonal influenza in children and adults

Live attenuated influenza vaccine (LAIV) is an intranasally administered trivalent, seasonal influenza vaccine that contains three live influenza viruses (two type A [H1N1 and H3N2 subtypes] and one type B). LAIV was effective in protecting against culture-confirmed influenza caused by antigenically matched and/or distinct viral strains in children aged ≤71 months enrolled in three phase III trials. LAIV was superior to trivalent inactivated influenza vaccine (TIV) in protecting against influenza caused by antigenically-matching viral strains in a multinational phase III trial in children aged 6-59 months. LAIV was also significantly more effective than TIV in decreasing the incidence of culture-confirmed influenza illness in two open-label studies (in children with recurrent respiratory tract illnesses aged 6-71 months and in children and adolescents with asthma aged 6-17 years). LAIV did not differ significantly from placebo in preventing febrile illnesses in adults (primary endpoint) enrolled in a phase III trial. However, LAIV significantly reduced the incidence of febrile upper respiratory tract illnesses (URTI), severe febrile illnesses, febrile URTI-related work absenteeism and healthcare provider use. In another well designed trial in adults, LAIV significantly reduced the incidence of symptomatic, laboratory-confirmed influenza compared with placebo (but not intramuscular TIV). LAIV was generally well tolerated in most age groups, with the majority of adverse events being mild to moderate in severity, and runny nose/nasal congestion being the most common. In a large phase III trial, LAIV, compared with TIV, was associated with an increased incidence of medically significant wheezing in vaccine-naive children aged <24 months and an increased incidence of hospitalization in children aged 6-11 months; LAIV is not approved for use in children <24 months. LAIV was not always associated with high rates of seroconversion/seroresponse, particularly in older children and adults, or in subjects with detectable levels of haemagglutination-inhibiting antibodies at baseline. However, LAIV did elicit mucosal (nasal) IgA antibody responses and strong cell-mediated immunity responses. Only one confirmed case of LAIV virus transmission to a placebo recipient (who did not become ill) occurred in a transmission study conducted in young children. The immunogenic response to LAIV in young healthy children was not affected by concomitant administration with other commonly administered childhood vaccines. In conclusion, intranasal LAIV seasonal influenza vaccine is effective and well tolerated in children, adolescents and adults. LAIV was more effective than TIV in children, although this advantage was not seen in adults. In the US, LAIV is indicated for the active immunization of healthy subjects aged 2-49 years against influenza disease caused by virus subtypes A and type B contained in the vaccine.

What determines influenza vaccination take-up of elderly Europeans?

We analyse the determinants of influenza vaccination take-up of Europeans above the age of 50 years using the first two waves of the Survey of Health, Ageing, and Retirement (SHARE). Using quality-of-care indicators, special emphasis is put on the measurement and the impact of physician quality. We find that age, health status, lifestyle, labour-force status, and the family structure are important determinants of the decision to get a flu shot. Physician quality, as measured by four indicators, also positively affects the probability of getting a flu shot.

Effectiveness of seasonal influenza vaccination in healthcare workers: a systematic review

Vaccination is considered a key measure to protect vulnerable groups against influenza infection. The objectives of this review are to determine the effect of influenza vaccinations in reducing laboratory-confirmed influenza infections, influenza-like illnesses (ILIs), working days lost among vaccinated HCWs, and associated adverse effects after vaccination. Twenty-two healthcare-related databases and internet resources, as well as reference lists, and the bibliographies of all of the retrieved articles were examined. All randomized controlled trials (RCTs) comparing the effectiveness of any kind of influenza vaccine among all groups of HCWs with a placebo/vaccine other than the influenza vaccine/no intervention were included in the review. Only three RCTs matched the inclusion criteria. There is a limited amount of evidence suggesting that receiving influenza vaccination reduces laboratory-confirmed influenza infections in HCWs. No evidence can be found of influenza vaccinations significantly reducing the incidence of influenza, number of ILI episodes, days with ILI symptoms, or amount of sick leave taken among vaccinated HCWs. There is insufficient data to assess the adverse effects after vaccination. There is no definitive conclusion on the effectiveness of influenza vaccinations in HCWs because of the limited number of related trials. Further research is necessary to evaluate whether annual vaccination is a key measure to protect HCWs against influenza infection and thus increase their confidence in the vaccine. In the mean time, the direction of promoting influenza vaccination to HCWs can be shifted from staff protection to patient protection, with accurate information to address concerns and misconceptions.