Inactivated Split Influenza Vaccine Research Articles

Trivalent mRNA vaccine-candidate against seasonal flu with cross-specific humoral immune response.

Seasonal influenza remains a serious global health problem, leading to high mortality rates among the elderly and individuals with comorbidities. Vaccination is generally accepted as the most effective strategy for influenza prevention. While current influenza vaccines are effective, they still have limitations, including narrow specificity for certain serological variants, which may result in a mismatch between vaccine antigens and circulating strains. Additionally, the rapid variability of the virus poses challenges in providing extended protection beyond a single season. Therefore, mRNA technology is particularly promising for influenza prevention, as it enables the rapid development of multivalent vaccines and allows for quick updates of their antigenic composition. mRNA vaccines have already proven successful in preventing COVID-19 by eliciting rapid cellular and humoral immune responses. In this study, we present the development of a trivalent mRNA vaccine candidate, evaluate its immunogenicity using the hemagglutination inhibition assay, ELISA, and assess its efficacy in animals. We demonstrate the higher immunogenicity of the mRNA vaccine candidate compared to the inactivated split influenza vaccine and its enhanced ability to generate a cross-specific humoral immune response. These findings highlight the potential mRNA technology in overcoming current limitations of influenza vaccines and hold promise for ensuring greater efficacy in preventing seasonal influenza outbreaks.

Supplementation of seasonal vaccine with multi-subtype neuraminidase and M2 ectodomain virus-like particle improves protection against homologous and heterologous influenza viruses in aged mice

The conventional inactivated split seasonal influenza vaccine offers low efficacy, particularly in the elderly and against antigenic variants. Here, to improve the efficacy of seasonal vaccination for the elderly population, we tested whether supplementing seasonal bivalent (H1N1 + H3N2) split (S) vaccine with M2 ectodomain repeat and multi-subtype consensus neuraminidase (NA) proteins (N1 NA + N2 NA + flu B NA) on a virus-like particle (NA-M2e) would induce enhanced cross-protection against different influenza viruses in aged mice. Immunization with split vaccine plus NA-M2e (S + NA-M2e) increased vaccine-specific IgG antibodies towards T-helper type 1 responses and hemagglutination inhibition titers. Aged mice with NA-M2e supplemented vaccination were protected against homologous and heterologous viruses at higher efficacies, as evidenced by preventing weight loss, lowering lung viral loads, inducing broadly cross-protective humoral immunity, and IFN-γ+ CD4 and CD8 T cell responses than those with seasonal vaccine. Overall, this study supports a new strategy of NA-M2e supplemented vaccination to enhance protection against homologous and antigenically different viruses in the elderly.

EFFECT OF PARENTERAL INFLUENZA VACCINATION ON THE CELL COMPOSITION AND ITS MICROBIOTA OF THE OROPHARYNGEAL SECRETION IN PATIENTS WITH CHRONIC INFLAMMATORY DISEASES OF THE UPPER RESPIRATORY TRACT

Relevance. Until recently, the issues of changes in immunological and microbiological parameters of the oropharynx in vaccinated against viral infections remain insufficiently covered.
 Objective: to determine the effect of parenteral influenza vaccination on the cellular and microbial composition of the oropharyngeal secretion in patients with chronic inflammatory diseases of the upper respiratory tract with the presence of anamnestic antibodies to vaccine strains of viruses.
 Materials and methods. Oropharyngeal secretion samples of 18 patients with chronic inflammatory diseases of the upper respiratory tract studied before and 3, 12, and 36 weeks after vaccination with inactivated split influenza vaccine. As control 25 donors were used. The cell composition of the sediment was determined. A microbiological study of the oropharyngeal secretion was performed.
 Results. At 3 and 12 weeks after vaccination, vaccinated patients significantly changed the relative rates of entry into the oropharyngeal secretion of lymphocytes and the composition of its microbiota while maintaining its total number. After 36 weeks, the cell composition and the representation of pathogenic and opportunistic microflora practically returned to baseline with a significant increase in the total microbiota.
 Conclusions. Parenteral administration of inactivated split vaccine to persons with chronic inflammatory diseases of the upper respiratory tract with the presence in the blood of anamnestic antibodies to vaccine strains of viruses is accompanied by a simultaneous temporary increase in lymphocyte representation with a simultaneous decrease in the number of transfusion microflora in the oropharyngeal secretion.

Актуальность профилактики гриппа и пневмококковой инфекции в период продолжающейся пандемии COVID-19

The article discusses the issues of vaccine prevention of influenza and pneumococcal infections during the ongoing pandemic of the new coronavirus infection COVID-19. Statistical data on the prevalence of these infections at the current time are provided. Co-infection can increase the symptoms of the diseases in these cases, and managing this condition is important for certain groups of patients. Respiratory viruses induce the attachment of pneumococcus, Pseudomonas aeruginosa and Hemophilus bacillus to the epithelial cells of the respiratory tract. The WHO position on influenza vaccination in the context of the COVID-19 pandemic is presented, and its main provisions are analyzed. Recommendations on the use of the main types of vaccines are given. Currently, the priority is to use 4-valent vaccines that ensure the development of the most stable immunity. In the Russian Federation, such a vaccine that meets all WHO recommendations is Ultrix Quadri, a tetravalent inactivated split influenza vaccine. The drug is a mixture of protective surface and internal antigens of influenza viruses of type A [subtypes A(H1N1) and A(H3N2)] and type B (Yamagata line and Victoria line). The use of vaccination schemes for pneumococcal infection was also discussed.

Safety and immunogenicity of a seasonal trivalent inactivated split influenza vaccine: a double blind, phase III randomized clinical trial in healthy Serbian adults.

This study was a phase III, multicenter, double-blind, randomized, placebo-controlled trial to evaluate the safety and immunogenicity of a seasonal trivalent split, inactivated influenza vaccine (TIV) in healthy Serbian adults between the ages of 18 and 65 years. This egg-based vaccine was manufactured by the Institute of Virology, Vaccines and Sera, Torlak, Belgrade, Serbia. A total of 480 participants were assigned randomly in a ratio of 2:1 to receive a single intramuscular dose (0.5 ml) of the vaccine (15 µg of hemagglutinin per strain) or placebo (phosphate-buffered saline). Participants were monitored for safety, including solicited and unsolicited adverse events (AEs) and serious adverse events (SAEs). No SAEs related to vaccination were reported. Injection site pain (51.3%), injection site tenderness (40.4%), tiredness (17.0%), and headache (15.1%) were the most commonly reported solicited events in the vaccine group. Incidence of related unsolicited AEs was low (1.3%) among vaccinees. Hemagglutinin inhibition (HAI) titers were measured before and 21 days after vaccination in 151 participants. Overall, HAI seroconversion rates to H1 and H3 were observed in 90.1% and 76.2% of vaccinees, respectively. For B antigen, it was 51.5%, likely due to high pre-vaccination titers. Post-vaccination seroprotection rates were in the range of 78.2–95.0% for the three antigens. Post-vaccination geometric mean titers (GMT) were at least 3.8 times higher than baseline levels for all the three strains among vaccinees. Overall, the study showed that the vaccine was safe and well tolerated, and induced a robust immune response against all three vaccine strains.ClinicalTrials.gov identifier: NCT02935192, October 17, 2016

Neuraminidase expressing virus-like particle vaccine provides effective cross protection against influenza virus

Neuraminidase is the second major surface antigen on influenza virus. We investigated the immunogenicity and cross protective efficacy of virus-like particle containing neuraminidase derived from 2009 pandemic H1N1 influenza virus (N1 VLP) in comparison with inactivated split influenza vaccine. Immunization of mice with N1 VLP induced antibody responses specific for virus and cross-reactive neuraminidase inhibition activity whereas an inactivated split vaccine induced strain-specific hemagglutination inhibition activity. N1 VLP-immunized mice developed cross protective immunity against antigenically different influenza viruses, as determined by body weight changes, lung viral titers, infiltrating innate immune cells, and cytokines, and antibody secreting cells, and germinal center B cells. Also, N1 VLP-immune sera provided cross-protection in naïve mice. Immunity by N1 VLP vaccination was not compromised in Fc receptor γ-chain deficient mice. These results suggest that neuraminidase-presenting VLP can be developed as an effective cross-protective vaccine candidate along with current influenza vaccination.

REACTOGENICITY, SAFETY AND IMMUNOGENICITY OF DOMESTIC FLU-M INACTIVATED SPLIT INFLUENZA VACCINE FOR THE IMMUNIZATION OF ADULTS AGED BETWEEN 18 AND 60

Aim. The research was aimed at evaluating the reactogenicity, safety and immunogenicity of Flu-M inactivated split influenza vaccine. Materials and methods. The reactogenicity, safety and immunogenicity of the drug were studied in the course of a multicenter, double blind, comparative, randomized clinical trial of immunized volunteers aged between 18 and 60 (comparator - Vaxigrip inactivated split vaccine for influenza prevention). Results. Domestic Flu-M inactivated split influenza vaccine manufactured by St. Petersburg Research Institute of Vaccines and Sera features favorable tolerability, high safety profile and adequate immunogenicity which is consistent with that of Vaxigrip influenza vaccine. Conclusion. Flu-M inactivated split influenza vaccine manufactured by St. Petersburg Research Institute of Vaccines and Sera can be recommended for authorization in the Russian Federation for the purpose of specific prophylaxis of influenza for adults aged between 18 and 60.

Efficacy, safety and immunogenicity of a trivalent inactivated split influenza vaccine in patients with rheumatic diseases

The aim of the study was to study the efficacy, safety and immunogenicity of trivalent split influenza vaccine in patients with rheumatoid arthritis (RA), ankylosing spondylitis (AS), systemic scleroderma (SSD). Material and methods. Ninety three patients were enrolled in the study, including 52 patients with RA, 34 with AS, 7 with SSD, and also 40 persons without rheumatic diseases (RD) (control group). At the time of enrolment, all patients received RD drug therapy. The duration of RD was from 2 months up to 46 years. Vaxigrip vaccine, which included the actual strains of influenza virus for the 2016-2017 or 2017-2018 seasons was administered subcutaneously in the amount of 1 dose (0.5 ml) against the backdrop of continuing RD therapy. The main stages of control were visits at 1-, 3- and 6-month intervals after vaccination. Standard clinical and laboratory tests, a clinical examination of the patient and assessment of disease activity were performed during the visits. Immunogenicity of the vaccine was evaluated at each stage of the control procedure using the commercial ELISA kits manufactured by PPDP LLC (St. Petersburg). Results. No cases of influenza or influenza-like illness were recorded during the entire period of observation. 81% of patients had no post-vaccination reactions in the RD group. Pain, swelling and hyperaemia of the skin with a diameter of up to 2 cm at the injection site were reported in 14% of cases and subfebrility, myalgia, malaise, headache in 5% of cases. The frequency of postvaccinal reactions among patients was not significantly different from that in the control group. There were no cases of exacerbation of RD or the occurrence of any new autoimmune disorders. The parameters of the humoral immune response in patients with RD did not significantly differ from those in the control group. Conclusion. The obtained data testify about good clinical efficacy and tolerability of trivalent split influenza vaccine in patients with RD.

Safety and immunogenicity of a seasonal trivalent inactivated split influenza vaccine: a phase I randomized clinical trial in healthy Serbian adults

ABSTRACTThis study was a phase I double-blind, randomized, placebo-controlled trial to evaluate the safety and immunogenicity of a Serbian-produced seasonal trivalent split, inactivated influenza vaccine in healthy adults. The vaccine was manufactured in eggs by the Torlak Institute of Virology, Vaccines and Sera, Belgrade, Serbia and contained A/H1N1, A/H3N2 and B viruses. The clinical trial took place at the Clinical Center of Serbia in Belgrade. Sixty healthy volunteers, aged 18–45 years, were enrolled in the trial. On the day of immunization, volunteers were randomly assigned to receive either a single dose of the trivalent seasonal influenza vaccine (15 μg of hemagglutinin per strain) or placebo (phosphate-buffered saline). Subjects were monitored for adverse events through a clinical history and physical examination, and blood was taken for testing at screening and on day 8 to assess vaccine safety. Serum samples obtained before and 21 days after immunization were tested for influenza antibody titers using hemagglutination-inhibition (HAI) and microneutralization (MN) tests. No serious adverse events were reported. Pain and tenderness at the injection site were the most commonly reported symptoms in both vaccine and placebo groups. Overall, serum HAI responses of fourfold or greater magnitude were observed to H1, H3, and B antigen in 80%, 75%, and 70% of subjects, respectively. Seroprotection rates as measured by HAI were also high (100%, 100% and 86.67%, respectively, for H1, H3 and B). Thus, Torlak's seasonal trivalent influenza vaccine was not associated with adverse events, was well-tolerated and immunogenic. It should be further evaluated in clinical trials to provide sufficient safety and immunogenicity data for licensing in Serbia.

Safety and effectiveness assessment of 2011–2012 seasonal influenza vaccine produced in China: a randomized trial

ABSTRACTObjective: This study evaluated the effectiveness and safety of the egg-based, trivalent, inactivated split influenza vaccine produced by the Institute of Medical Biology, Chinese Academy of Medical Sciences, Peking Union Medical College, China.Methods: From March 2012 through May 2012, we enrolled a total of 1390 healthy volunteers between the ages of 3 and 80 years in a randomized clinical trial at the Hebei Disease Control Center Vaccine Clinical Evaluation Center. For all subjects, body part adverse reactions and whole-body adverse reactions were observed 30 min, 6 h, and 1–7 days’ post-inoculation. If no severe adverse effects were observed 7 days’ post-vaccination, the local and systemic reactions of preliminary test participants were recorded until day 28. There was no placebo group in this study. Blood samples were taken for serological testing before vaccination and 28 days’ post-vaccination.Results: Twenty-eight days after vaccination, the seroconversion rates of experimental and control groups were H1N1 75.3% and 75.7%, H3N2 75.8% and 71.8%, B 70.7% vs. 69.4%, (P > 0.05). The antibody Geometric Mean Titer（GMT）of experimental and control groups were H1N1 (179.7, 182.4), H3N2 (584.0, 445.7), B (201.4,191.6). The protection rate of experimental and control groups was not statistically significant (H1N1: 86% vs. 87%, H3N2: 99% vs. 98%, B: 98% vs. 98%). Also, 95% confidence intervals of the protection rate difference between the experimental and the control group were H1N1: −0.1% (−4.1,3.8) %, H3N2: 0.3% (−1.0,1.7) % and B: 0.2% (−1.5,1.9) %; confidence intervals exceeded the limit of −5%. The rates of adverse reactions between experimental and control groups were 6.3% and 7.7% in local response reactions, and 19.5% and 18.0% in systemic reactions. Three hundred and twenty-seven adverse events (AEs) in 1200 (27.76%) subjects were reported within 28 d after vaccination. No serious adverse events occurred during the study.Conclusions: The experimental vaccine three-antibody protection rate was non-inferior to the control vaccine. Our results demonstrated that the experimental vaccine achieved the primary immunogenic end point of the intended clinical protocol, as well as a secondary immunogenic end-point, with an acceptable level of safety. IRB approval for this study was issued under #2012Y0005 and registered as Clinical Trial No. NCT01551810.

Distinct Effects of Monophosphoryl Lipid A, Oligodeoxynucleotide CpG, and Combination Adjuvants on Modulating Innate and Adaptive Immune Responses to Influenza Vaccination.

Monophosphoryl lipid A (MPL) and oligodeoxynucleotide CpG are toll-like receptor (TLR) 4 and 9 agonist, respectively. Here, we investigated the effects of MPL, CpG, and combination adjuvants on stimulating in vitro dendritic cells (DCs), in vivo innate and adaptive immune responses, and protective efficacy of influenza vaccination. Combination of MPL and CpG was found to exhibit distinct effects on stimulating DCs in vitro to secrete IL-12p70 and tumor necrosis factor (TNF)-α and proliferate allogeneic CD8 T cells. Prime immunization of mice with inactivated split influenza vaccine in the presence of low dose MPL+CpG adjuvants increased the induction of virus-specific IgG and IgG2a isotype antibodies. MPL and CpG adjuvants contribute to improving the efficacy of prime influenza vaccination against lethal influenza challenge as determined by body weight monitoring, lung function, viral titers, and histology. A combination of MPL and CpG adjuvants was effective in improving vaccine efficacy as well as in reducing inflammatory immune responses locally and in inducing cellular immune responses upon lethal influenza virus challenge. This study demonstrates unique adjuvant effects of MPL, CpG, and combination adjuvants on modulating innate and adaptive immune responses to influenza prime vaccination.

Technology transfer of oil-in-water emulsion adjuvant manufacturing for pandemic influenza vaccine production in Romania: Preclinical evaluation of split virion inactivated H5N1 vaccine with adjuvant

abstractMillions of seasonal and pandemic influenza vaccine doses containing oil-in-water emulsion adjuvant have been administered in order to enhance and broaden immune responses and to facilitate antigen sparing. Despite the enactment of a Global Action Plan for Influenza Vaccines and a multi-fold increase in production capabilities over the past 10 years, worldwide capacity for pandemic influenza vaccine production is still limited. In developing countries, where routine influenza vaccination is not fully established, additional measures are needed to ensure adequate supply of pandemic influenza vaccines without dependence on the shipment of aid from other, potentially impacted first-world countries. Adaptation of influenza vaccine and adjuvant technologies by developing country influenza vaccine manufacturers may enable antigen sparing and corresponding increases in global influenza vaccine coverage capacity. Following on previously described work involving the technology transfer of oil-in-water emulsion adjuvant manufacturing to a Romanian vaccine manufacturing institute, we herein describe the preclinical evaluation of inactivated split virion H5N1 influenza vaccine with emulsion adjuvant, including immunogenicity, protection from virus challenge, antigen sparing capacity, and safety. In parallel with the evaluation of the bioactivity of the tech-transferred adjuvant, we also describe the impact of concurrent antigen manufacturing optimization activities. Depending on the vaccine antigen source and manufacturing process, inclusion of adjuvant was shown to enhance and broaden functional antibody titers in mouse and rabbit models, promote protection from homologous virus challenge in ferrets, and facilitate antigen sparing. Besides scientific findings, the operational lessons learned are delineated in order to facilitate adaptation of adjuvant technologies by other developing country institutes to enhance global pandemic influenza preparedness.

Immunological persistence of a seasonal influenza vaccine in people more than 3 years old

To evaluate antibody persistence of Aleph inactivated split influenza vaccine, 3308 healthy Chinese people more than 3 years old were enrolled in a hemagglutination inhibition (HI) assay before vaccination, 641 were screened by HI assay negative, 437 of which received one dose of Aleph inactivated split influenza vaccine and 204 of which received one dose of control vaccine (recombinant hepatitis B). After vaccination, the receivers were collected blood at 1st month, 3rd month, 6th month and 12th month for Aleh influenza vaccine antibody persistence assess. The antibody test were determined by hemagglutination inhibition (HI) assay. There were significant difference in antibody geometric mean titer between experimental group and control at 1st month and 3rd month after vaccination. Influenza antibody could persist at least up to 3rd month. Because of the local spring influenza epidemic, we could not analyze the results of 6th and 12th month. Aleph influenza vaccines showed good immune persistence in healthy volunteers at least in the 3 months after vaccination. Influenza viruses are important human respiratory pathogens. Immunization is widely acknowledged to currently be the most effective method of minimizing the impact of pandemic influenza. Through we have checked many references about Influenza vaccine, the duration of protective antibody for influenza vaccines are still not available. Based on this situation and our previous work,11 Influenza vaccine antibody duration analyze are necessary. This manuscript presents data on the persistence of Hemagglutination Inhibition (HI) immune response against the A/California/7/2009(H1N1), A/Peth/16/2009(H3N2) strain and B/Brisbane/60/2008. 641 were screened from 3302 volunteers by HI test of influenza A and confirmed enrollment based on the antibodies titer less than 1:10. After administered with one dose of Aleph influenza vaccine, blood samples were collected. 437 subjects (3–10y: 131; 11–17y: 110; 18–54y: 69; ≥55y: 127) were vaccinated influenza vaccine as test group. 204 subjects (3–10 y: 70; 11–17 y: 47; 18–54 y: 28; ≥55 y: 59) were vaccinated recombinant hepatitis B vaccine as control group. Immunogenicity end points were based on the European licensure criteria for pandemic influenza vaccines. The persistence of HI immune response against the vaccine strain was assessed through GMT. The immunogenicity of the Aleph influenza vaccine induced all reached the standards at 1st month and GMTs peak could persist at least up to 3rd month. (This study has been registered at clinicaltrials.gov under registration no. NCT01758185.) Because of the local spring influenza epidemic we could not analyze the results of 6th and 12th month. Aleph influenza vaccines showed good immune persistence in healthy volunteers at least in the 3 months after vaccination.

Immunogenicity and safety assessment of a trivalent, inactivated split influenza vaccine in Korean children: Double-blind, randomized, active-controlled multicenter phase III clinical trial

A multicenter, double-blind, randomized, active-control phase III clinical trial was performed to assess the immunogenicity and safety of a trivalent, inactivated split influenza vaccine. Korean children between the ages of 6 months and 18 y were enrolled and randomized into a study (study vaccine) or a control vaccine group (commercially available trivalent, inactivated split influenza vaccine) in a 5:1 ratio. Antibody responses were determined using hemagglutination inhibition assay, and post-vaccination immunogenicity was assessed based on seroconversion and seroprotection rates. For safety assessment, solicited local and systemic adverse events up to 28 d after vaccination and unsolicited adverse events up to 6 months after vaccination were evaluated. Immunogenicity was assessed in 337 and 68 children of the study and control groups. In the study vaccine group, seroconversion rates against influenza A/H1N1, A/H3N2, and B strains were 62.0% (95% CI: 56.8–67.2), 53.4% (95% CI: 48.1–58.7), and 54.9% (95% CI: 48.1–60.2), respectively. The corresponding seroprotection rates were 95.0% (95% CI: 92.6–97.3), 93.8% (95% CI: 91.2–96.4), and 95.3% (95% CI: 93.0–97.5). The lower 95% CI limits of the seroconversion and seroprotection rates were over 40% and 70%, respectively, against all strains. Seroconversion and seroprotection rates were not significantly different between the study and control vaccine groups. Furthermore, the frequencies of adverse events were not significantly different between the 2 vaccine groups, and no serious vaccination-related adverse events were noted. In conclusion, the study vaccine exhibited substantial immunogenicity and safety in Korean children and is expected to be clinically effective.

A randomized, controlled, blinded study of the safety, immunogenicity and batch consistency of Aleph inactivated split influenza vaccine made in China in Chinese people

To evaluate the safety, immunogenicity and batch consistency of Aleph inactivated split influenza vaccine, 3308 healthy Chinese people more than 3 years old were enrolled in a randomized, controlled, blinded study and divided into four age groups: 3–10 years, 11–17 years, 18–54 years, and more than 55 years. Each age group was then randomized (2:1) to receive either influenza vaccine or control vaccine (recombinant hepatitis B) for one dose. Also each influenza vaccine group was randomized (1:1:1) to receive three different batches of influenza vaccine. Systematic and local adverse reactions for 28 days after vaccination were recorded, and influenza antibody titer was determined by hemagglutination inhibition (HI) assay at 28 days after vaccination. There were significant differences in seroconversion and seroprotection rates achieved post-immunization of three strains of influenza antibody (H1N1, H3N2, B) between experimental group and control group in all age groups (P < 0.05). In addition, there were no statistically significant differences in local and systematic reaction rates after vaccination between the experimental and control group in all age groups (P > 0.05), except for the systematic reaction rates in the 18–54 years and ≥ 55 years age groups (P < 0.05). Thus, Aleph inactivated split influenza vaccine has good safety and immunogenicity.

Neuraminidase-Inhibiting Antibody Is a Correlate of Cross-Protection against Lethal H5N1 Influenza Virus in Ferrets Immunized with Seasonal Influenza Vaccine

In preparing for the threat of a pandemic of avian H5N1 influenza virus, we need to consider the significant delay (4 to 6 months) necessary to produce a strain-matched vaccine. As some degree of cross-reactivity between seasonal influenza vaccines and H5N1 virus has been reported, this was further explored in the ferret model to determine the targets of protective immunity. Ferrets were vaccinated with two intramuscular inoculations of trivalent inactivated split influenza vaccine or subcomponent vaccines, with and without adjuvant, and later challenged with a lethal dose of A/Vietnam/1203/2004 (H5N1) influenza virus. We confirmed that vaccination with seasonal influenza vaccine afforded partial protection against lethal H5N1 challenge and showed that use of either AlPO(4) or Iscomatrix adjuvant with the vaccine resulted in complete protection against disease and death. The protection was due exclusively to the H1N1 vaccine component, and although the hemagglutinin contributed to protection, the dominant protective response was targeted toward the neuraminidase (NA) and correlated with sialic acid cleavage-inhibiting antibody titers. Purified heterologous NA formulated with Iscomatrix adjuvant was also protective. These results suggest that adjuvanted seasonal trivalent vaccine could be used as an interim measure to decrease morbidity and mortality from H5N1 prior to the availability of a specific vaccine. The data also highlight that an inducer of cross-protective immunity is the NA, a protein whose levels are not normally monitored in vaccines and whose capacity to induce immunity in recipients is not normally assessed.

Challenge of conducting a placebo-controlled randomized efficacy study for influenza vaccine in a season with low attack rate and a mismatched vaccine B strain: a concrete example

BackgroundOur aim was to determine the efficacy of a trivalent inactivated split virus influenza vaccine (TIV) against culture-confirmed influenza A and/or B in adults 18 to 64 years of age during the 2005/2006 season in the Czech Republic.Methods6203 subjects were randomized to receive TIV (N = 4137) or placebo (N = 2066). The sample size was based on an assumed attack rate of 4% which provided 90% power to reject the hypothesis that vaccine efficacy (VE) was ≥ 45%. Cases of influenza like illness (defined as fever (oral temperature ≥37.8°C) plus cough and/or sore throat) were identified both by active (biweekly phone contact) and passive (self reporting) surveillance and nasal and throat swabs were collected from subjects for viral culture.ResultsTIV was well tolerated and induced a good immune response. The 2005/2006 influenza season was exceptionally mild in the study area, as it was throughout Europe, and only 46 culture-confirmed cases were found in the study cohort (10 influenza A and 36 influenza B). Furthermore among the B isolates, 35 were identified as B/Hong Kong 330/2001-like (B/Victoria/2/87 lineage) which is antigenically unrelated to the vaccine B strain (B/Yamagata/16/88 lineage). The attack rate in the vaccine group (0.7%) was not statistically significantly different from the attack rate in the placebo group (0.9%).ConclusionDue to the atypical nature of the influenza season during this study we were unable to assess TIV efficacy. This experience illustrates the challenge of conducting a prospective influenza vaccine efficacy trial during a single season when influenza attack rates and drift in circulating strains or B virus lineage match can be difficult to estimate in advance.Trial RegistrationClinical trial registery: NCT00197223.

The safety and immunogenicity of influenza vaccine in children with asthma in Mexico

The morbidity and mortality associated with influenza is substantial in children with asthma. There are no available data on the safety and immunogenicity of influenza vaccine in children with asthma in Latin America. Furthermore, it is unclear if influenza vaccination may cause asthma exacerbations. We conducted a placebo-controlled trial to investigate the safety and immunogenicity of an inactivated trivalent split virus influenza vaccine in children with asthma in Mexico. We also measured the impact of influenza vaccination on pulmonary function tests in this population. The inactivated influenza vaccine was immunogenic and safe in terms of local and systemic side effects compared to placebo. We observed no significant impact on pulmonary function tests among vaccine recipients. Given the significant morbidity associated with influenza in children, strategies to promote increased influenza vaccination coverage in this high-risk group in Latin America and elsewhere are urgently needed.

Immunogenicity of a reduced dose of A/H3N2 in the 2005 southern hemisphere formulation of inactivated split influenza vaccine

The 2005 southern hemisphere formulation of the inactivated split-virion influenza vaccine Vaxigrip unintentionally contained a lower concentration of haemagglutinin (HA) than European Pharmacopoeia (EP) and WHO specifications for one of the three strains. To evaluate the immunogenicity of the 2005 southern hemisphere formulation of an influenza vaccine containing 9 microg/dose of HA for A/Wellington/1/2004(H3N2) strain, and 15 microg/dose for each of the A/New Caledonia/20/99(H1N1) strain and B/Shanghai/361/2002-like strains. In an open, non-controlled multicentre clinical trial, 75 healthy adults (18-59 years) and 65 healthy older adults (> or =60 years) were vaccinated once. Serum samples were obtained on D0 and 21 for haemagglutination inhibition (HAI) antibody titration. A high proportion of adults (64%) and elderly (68%) were already seroprotected (HAI titre of > or =40) against A/Wellington/1/2004(H3N2) before vaccination, probably due to high circulation of an antigenically similar H3N2 strain and a high 2004 vaccination rate. By D21, seroprotection rates against H3N2 attained 93.8% and 96.0% in adults and elderly respectively. The other two immunogenicity criteria for annual licensure of influenza vaccines in Europe were also met in both age groups for the H3N2 strain, and also for the H1N1 and B strains. These results enabled the 2005 southern hemisphere vaccine to be used in expectation that it would provide satisfactory protection against influenza, despite the reduced H3N2 antigen content.

Long-term clinical trial safety experience with the inactivated split influenza vaccine, Vaxigrip ®

Safety data on the inactivated split influenza vaccine, Vaxigrip ®, were compiled and analysed from 28 clinical trials (total: 4599 subjects aged 6 months to 99 years) to provide a robust estimate of the reactogenicity profile. The most frequent solicited reactions were non-severe injection site pain and erythema in children, adults, and elderly. Mild or moderate fever was the most frequent reaction in 6–36 months olds; few systemic reactions were reported in older groups. Reactogenicity was comparable in healthy and high-risk children. The long-term experience with the world's most widely used influenza vaccine, Vaxigrip ®, confirms its excellent tolerability, and supports its continued use in clinical practice worldwide.