The risk of major structural birth defects associated with seasonal influenza vaccination during pregnancy: A population-based cohort study.

INTRODUCTION: Seasonal inactivated influenza vaccine (IIV) is routinely recommended during pregnancy to protect both mothers and infants from complications following influenza infection. While previous studies have evaluated the risk of major structural birth defects in infants associated with prenatal administration of monovalent pandemic IIV, fewer studies have evaluated the risk associated with prenatal seasonal IIV. METHODS: We conducted a population-based cohort study of 125,866 singleton births between 2012 and 2016 in Western Australia. Birth registrations were linked to the state's registers for congenital anomalies and a state prenatal vaccination database. We estimated prevalence ratios (PR) of any major structural birth defect and defects by organ system. Vaccinated pregnancies were defined as those with a record of IIV in the first trimester. Inverse probability treatment weighting factored for baseline probability for vaccination. A Bonferroni correction was applied to account for multiple comparisons. RESULTS: About 3.9% of births had a major structural birth defect. Seasonal IIV exposure during the first trimester was not associated with diagnosis of any major structural birth defect diagnosed within 1 month of birth (PR 0.98, 95% CI: 0.77, 1.28) or within 6 years of life (PR 1.02, 95% CI: 0.78, 1.35). We identified no increased risk in specific birth defects associated with seasonal IIV. CONCLUSION: Based on registry data for up to 6 years of follow-up, results suggest there is no association between maternal influenza vaccination and risk of major structural birth defects. These results support the safety of seasonal IIV administration during pregnancy.

Preclinical evaluation of the safety and pathogenicity of a live attenuated recombinant influenza A/H7N9 seed strain and corresponding MF59-adjuvanted split vaccine.

Developing a safe and effective H7N9 influenza vaccine was initiated in early spring 2013, following human infections with a novel avian influenza A (H7N9) virus. In this study, a candidate H7N9 vaccine seed strain is produced using reverse genetics, with HA and NA derived from a human H7N9 virus and the remaining genes from the PR8 backbone virus which grows well in eggs. We verified that the virulence and transmissibility of the recombinant H7N9 vaccine seed strain were decreased as compared to wild-type H7N9 virus, to levels comparable with PR8. Using the seed virus, we produced a monovalent split influenza A (H7N9) MF59-adjuvanted vaccine that was immunogenic in mice. Our H7N9 vaccine is selected for clinical investigation and potential human use. To assess the safety of our H7N9 vaccine, we performed acute toxicity, repeated dose toxicity and active systemic anaphylaxis tests. Our results showed that, under the conditions used in this study, the NOEAL (no obvious adverse effect level) was 30 µg/0.5 mL.

Pharmacokinetics and biodistribution of squalene-containing emulsion adjuvant following intramuscular injection of H5N1 influenza vaccine in mice.

Squalene is a component of oil-in-water emulsion adjuvants developed for potential use in some influenza vaccines. The biodistribution of the squalene-containing emulsion adjuvant (AddaVax™) alone and as part of complete H5N1 vaccine was quantified in mechanistically and toxicologically relevant target tissues up to 336 h (14 days) following injection into quadriceps muscle. At 1 h, about 55% of the intramuscularly injected dose of squalene was detected in the local quadriceps muscles and this decreased to 26% at 48 h. Twenty-four hours after the injection, approximately 5%, 1%, and 0.6% of the injected dose was detected in inguinal fat, draining lymph nodes, and sciatic nerve, respectively. The peak concentration for kidney, brain, spinal cord, bone marrow, and spleen was each less than 1% of the injected dose, and H5N1 antigen did not significantly alter the biodistribution of squalene to these tissues. The area-under-blood-concentration curve (AUC) and peak blood concentration (Cmax) of squalene were slightly higher (20-25%) in the presence of H5N1 antigen. A population pharmacokinetic model-based statistical analysis identified body weight and H5N1 antigen as covariates influencing the clearance of squalene. The results contribute to the body of knowledge informing benefit-risk analyses of squalene-containing emulsion vaccine adjuvants.

Non-clinical safety and biodistribution of AS03-adjuvanted inactivated pandemic influenza vaccines.

Pandemic-influenza vaccines containing split-inactivated-virus antigen have been formulated with the immunostimulatory Adjuvant System AS03 to enhance the antigen immunogenicity and reduce antigen content per dose. AS03 is an oil-in-water emulsion containing α-tocopherol, squalene and polysorbate 80. To support the clinical development of AS03-adjuvanted pandemic-influenza vaccines, the local and systemic toxicity of test articles containing split-influenza A(H5N1) and/or AS03 were evaluated after 3-4 intramuscular (i.m.) injections in rabbits. Treatment-related effects were restricted to mild inflammatory responses and were induced primarily by the test articles containing AS03. The injection-site inflammation was mild at 3 days, and minimal at 4 weeks after the last injection; and was reflected by signs of activation in the draining lymph nodes and by systemic effects in the blood including a transient increase of neutrophils. In addition, a study in mice explored the biodistribution of A(H5N1) vaccines or AS03 through radiolabelling the antigen or constituents of AS03 prior to injection. In this evaluation, 57-73% of AS03's principal constituents had cleared from the injection site 3 days after injection, and their different clearance kinetics were suggestive of AS03's dissociation. All these AS03 constituents entered into the draining lymph nodes within 30 min after injection. In conclusion, the administration of repeated doses of the H5N1/AS03 vaccine was well tolerated in the rabbit, and was primarily associated with transient mild inflammation at the injection site and draining lymph nodes. The biodistribution kinetics of AS03 constituents in the mouse were consistent with AS03 inducing this pattern of inflammation.

Functional testing of an inhalable nanoparticle based influenza vaccine using a human precision cut lung slice technique.

Annual outbreaks of influenza infections, caused by new influenza virus subtypes and high incidences of zoonosis, make seasonal influenza one of the most unpredictable and serious health threats worldwide. Currently available vaccines, though the main prevention strategy, can neither efficiently be adapted to new circulating virus subtypes nor provide high amounts to meet the global demand fast enough. New influenza vaccines quickly adapted to current virus strains are needed. In the present study we investigated the local toxicity and capacity of a new inhalable influenza vaccine to induce an antigen-specific recall response at the site of virus entry in human precision-cut lung slices (PCLS). This new vaccine combines recombinant H1N1 influenza hemagglutinin (HAC1), produced in tobacco plants, and a silica nanoparticle (NP)-based drug delivery system. We found no local cellular toxicity of the vaccine within applicable concentrations. However higher concentrations of NP (≥10(3) µg/ml) dose-dependently decreased viability of human PCLS. Furthermore NP, not the protein, provoked a dose-dependent induction of TNF-α and IL-1ß, indicating adjuvant properties of silica. In contrast, we found an antigen-specific induction of the T cell proliferation and differentiation cytokine, IL-2, compared to baseline level (152±49 pg/mg vs. 22±5 pg/mg), which could not be seen for the NP alone. Additionally, treatment with 10 µg/ml HAC1 caused a 6-times higher secretion of IFN-γ compared to baseline (602±307 pg/mg vs. 97±51 pg/mg). This antigen-induced IFN-γ secretion was further boosted by the adjuvant effect of silica NP for the formulated vaccine to a 12-fold increase (97±51 pg/mg vs. 1226±535 pg/mg). Thus we were able to show that the plant-produced vaccine induced an adequate innate immune response and re-activated an established antigen-specific T cell response within a non-toxic range in human PCLS at the site of virus entry.

Animal models to assess the toxicity, immunogenicity and effectiveness of candidate influenza vaccines.

INTRODUCTION: Every year, > 100 million doses of licensed influenza vaccine are administered worldwide, with relatively few serious adverse events reported. Initiatives to manufacture influenza vaccines on different platforms have come about to ensure timely production of strain-specific as well as universal vaccines. To prevent adverse events that may be associated with these new vaccines, it is important to evaluate the toxicity of new formulations in animal models. AREAS COVERED: This review outlines preclinical studies that evaluate safety, immunogenicity and effectiveness of novel products to support further development and clinical trials. This has been done through a review of the latest literature describing vaccines under development. EXPERT OPINION: The objective of preclinical safety tests is to demonstrate the absence of toxic contaminants and adventitious agents. Additional tests that characterize vaccine content more completely, or demonstrate the absence of exacerbated disease following virus challenge in vaccinated animals, may provide additional data to ensure the safety of new vaccine strategies.

[New evaluation methods of vaccine safety].

In this study, we showed, using comprehensive gene expression analysis, that pertussis and pandemic influenza vaccine affected many lung genes. The 13 and 76 genes were extracted from the pertussis vaccine- and pandemic influenza vaccine-treated lung at day 1, respectively. Furthermore, QuantiGene Plex methods, quantitative analysis of the expression of these genes could detect the toxicity from samples containing various concentrations of reference pertussis vaccines. Our findings and methods provide the first assessment for the influence of vaccine toxicity with an approach using experimental biology and genome science.

[Attitudes of family physicians to influenza vaccination after a cluster of deaths that were initially attributed to the vaccination].

BACKGROUND: The influenza vaccination rates in high risk populations decreased in 2006, in part, perhaps, as a reaction to a cluster of deaths that were initially attributed to the vaccine. We postulated that this event affected family physicians who usually recommend vaccination, and caused a change in their prescribing behavior. OBJECTIVES: To survey family physicians as to their recommendation of the influenza vaccine in 2006 as opposed to the previous year. METHODS: After the 2006 influenza vaccination season an anonymous questionnaire was distributed in various settings to family physicians. The questions related to prescribing behavior in various target populations and whether they vaccinate themselves and their families. RESULTS: A total of 122 physicians responded; 74.5% thought that there was minimal or no connection between the vaccine and the deaths, 75.8% also denied any change in their recommendation behavior. However, there was a significant decrease in the recommendation strength as seen in the percentage of physicians who reported very strong recommendations to the elderly (57.4% vs. 32.3%, p < 0.05) and chronically ill patients (64.8% vs. 39%, p < 0.05). No difference was seen in their reported personal vaccination behavior. A multivariate regression model did not find any correlations between characteristics of the responding physicians and their attitudes or changes in attitudes to the influenza vaccine. CONCLUSIONS: The family physicians were more hesitant in recommending the influenza vaccine in 2006, and this may have affected vaccination rates. Improved availability of information and guidance to family physicians after the cluster of deaths may have prevented this.

Toxicological evaluation of live attenuated, cold-adapted H5N1 vaccines in ferrets.

Live attenuated influenza vaccines (LAIV) have several attributes related to safety, immunogenicity, cross-protection against antigenic drift strains, high yield and needle-free administration that make them attractive candidates for control of pandemic influenza. H5N1 LAIV vaccine candidates are attenuated in ferrets, chickens and mice. These vaccine candidates were further characterized in the ferret model to evaluate their toxicity at doses comparable to seasonal LAIV and at doses up to 100-fold higher. The results demonstrated that H5N1 LAIV, even when administered at high doses, is restricted in replication in the lower respiratory tract of ferrets. However, intranasal administration of 0.5 mL can result in deposition of H5N1 LAIV in the ferret lung, where it induces a pulmonary inflammatory response in the absence of significant local replication of the vaccine virus. Thus, smaller vaccine dose volumes should be considered for evaluation of LAIV in animal models.

Development of immune response that protects mice from viral pneumonitis after a single intranasal immunization with influenza A virus and nanoemulsion.

Nanoemulsion, a water-in-oil formulation stabilized by small amounts of surfactant, is non-toxic to mucous membranes and produces biocidal activity against enveloped viruses. We evaluated nanoemulsion as an adjuvant for mucosal influenza vaccines. Mice (C3H/HeNHsd strain) were vaccinated intranasally with 5 x 10(5) plaque forming units (pfu) of influenza A virus (Ann Arbor/6/60 strain) and a nanoemulsion mixture. The mice were challenged on day 21 after immunization with an intranasal lethal dose of 2 x 10(5) pfu of virus. Animals vaccinated with the influenza A/nanoemulsion mixture were completely protected against infection, while animals vaccinated with either formaldehyde-killed virus or nanoemulsion alone developed viral pneumonitis and died by day 6 after the challenge. Mice vaccinated with virus/nanoemulsion mixture had rapid cytokine responses followed by high levels of specific anti-influenza immunoglobulin G (IgG) and immunoglobulin A (IgA) antibodies. Specificity of the immune response was confirmed by assessment of the proliferation and cytokine production in splenocytes. This paper demonstrates that nanoemulsion can be employed as a non-toxic mucosal adjuvant for influenza virus vaccine.

Nonclinical safety evaluation of Escherichia coli heat-labile toxin mucosal adjuvant as a component of a nasal influenza vaccine.

Conventional influenza vaccines currently in use are administered parenterally and generally confer good protection against systemic disease through the induction of high titers of serum virus-neutralizing antibodies. Parenteral vaccines are suboptimal in that they fail to induce a local mucosal response that may prevent the early stages of virus infection. Thus, the intranasal administration of a vaccine may provide a viable alternative to the parenteral route. Indeed, intranasal administration of vaccine antigens when formulated with an appropriate mucosal adjuvant (e.g., bacterial toxins), results in a vigorous local and systemic immune response. This review discusses the nonclinical safety evaluation of Escherichia coli heat-labile toxin as a mucosal adjuvant for an intranasally administered influenza vaccine.

Antibody-forming cell response to virus challenge in mice immunized with DNA encoding the influenza virus hemagglutinin.

Immunization of mice with DNA encoding the influenza virus hemagglutinin (HA) affords complete protection against lethal influenza virus infection and the means to investigate the mechanisms of B-cell responsiveness to virus challenge. Using a single-cell enzyme-linked immunospot assay, we sought to determine the localization of HA-specific antibody-forming cells (AFCs) during the development of humoral immunity in mice given HA DNA vaccine by gene gun. At 33 days postvaccination, populations of AFCs were maintained in the spleen and bone marrow. In response to lethal challenge with influenza virus, the AFCs became localized at the site of antigenic challenge, i.e., within the draining lymph nodes of the lung compartment. Immunoglobulin G (IgG)- and IgA-producing AFCs were detected in lymph nodes of the upper and lower respiratory tracts, underscoring their importance in clearing virus from the lungs. Response to challenge required competent CD4+ T cells, without which no AFCs were generated, even those producing IgM. By contrast, in mice vaccinated with an HA-containing subunit vaccine, fewer AFCs were generated in response to challenge, and these animals were less capable of resisting infection. Our findings demonstrate the comparable localization of AFCs in response to challenge in mice vaccinated with either HA DNA or live virus. Moreover, the former strategy generates both IgG- and IgA-producing plasma cells.

An update on approaches to the development of respiratory syncytial virus (RSV) and parainfluenza virus type 3 (PIV3) vaccines.

RSV and PIV3 are responsible for about 30% of severe viral respiratory tract disease leading to hospitalization of infants and children. For this reason, there is a need to develop vaccines effective against these viruses. Since these viruses cause severe disease in early infancy, vaccines must be effective in the presence of maternal antibody. Currently, several strategies for immunization against these viruses are being explored including peptide vaccines, subunit vaccines, vectored vaccines (e.g., vaccinia-RSV or adenovirus-RSV recombinants), and live attenuated virus vaccines. The current status of these approaches is reviewed. In addition, the immunologic basis for the disease potentiation seen in vaccinees immunized with formalin-inactivated RSV during subsequent RSV infection is reviewed. The efficacy of immunization in the presence of maternal antibody is discussed. Much progress for a RSV and PIV3 vaccine has been made and successful immunization against each of these pathogens should be achieved within this decade.

[Determination of bacterial endotoxin admixtures in inactivated influenza vaccines]. / Opredelenie primesei bakterial'nykh éndotoksinov v inaktivirovannykh grippoznykh vaktsinakh.

The materials substantiating the possibility of using the method for the determination of the lethal effect of endotoxin on dactinomycin-treated mice are presented. This determination is made with a view to detecting the admixtures of endotoxins in whole-virion and subvirion inactivated influenza vaccines at different stages of their manufacture, as well as in the final product. The proposed test is highly sensitive, rather simple in its practical realization and can be used for evaluating the degree of the purification of influenza vaccines from endotoxins.

[Safety and effectiveness study of the aerosol method of administering inactivated influenza chromatographic vaccine in an experiment]. / Izuchenie bezvrednosti i éffektivnosti aérozol'nogo metoda vvedeniia inaktivirovannoi grippoznoi khromatograficheskoi vaktsiny v éksperimente.

Experiments in laboratory animals demonstrated safety, areactogenicity, and low allergenic potential of inactivated influenza chromatographic vaccine (IICV) administered by aerosol method. Aerosol immunization of white rats resulted in the development of the same level of secretory antibody as after intraperitoneal inoculation of IICV but the immunizing aspirational dose was 10-20 times as low as parenteral. Marked protection of mice was achieved after triple aerosol immunization of immunologically experienced animals.

[Biological properties of live and inactivated influenza vaccines under experimental conditions]. / Izuchenie biologicheskikh svoistv zhivykh i inaktivirovannykh protivogrippoznykh vaktsin v éksperimental'nykh usloviiakh.

Biological properties of influenza vaccines were studied on experimental animals inoculated intraperitoneally with regard to the vaccine effect on peritoneal exudate cells. The development of neutrophilia and inhibition of acid phosphatase activity in macrophages within the first 24 hours after intraperitoneal inoculation of influenza viruses or influenza vaccines were used for determination of the toxic effect of the inoculum. The values of subsequent later activation of acid phosphatase in macrophages allowed the immunogenic properties of the vaccines under study to be evaluated. The sensitizing properties of the virus antigens were assessed by the reaction of the lymphoid-macrophage system after multiple inoculations of the preparations. A correlation of changes observed in the experimental animals with reactogenicity and values of immunity against influenza in man and animals was established.

Prospects of a living attenuated vaccine against influenza.

Living attenuated vaccines offer the promise of providing more effective immunity against influenza than inactivated vaccines. However, the development of such vaccines presents unique problems, because influenza A viruses undergo frequent antigenic change and are highly infectious. Ideally, a living vaccine should produce substantial immunity to the disease from a single dose administered in the form of nose drops. The vaccine should be suitably attenuated, with attenuation being determined by in vitro markers which allow the ready detection of revertants to virulence. The only practical approach is to use a thoroughly accredited master strain which can be recombined with a contemporary virulent strain to produce an attenuated recombinant having the surface antigens of the contemporary strain. Of the master strains currently being developed, temperature-sensitive (ts) and cold-adapted (ca) mutants appear to have the greatest promise.

A study of live influenza virus vaccine in patients with chronic bronchitis. Report to Medical Research Council's Committee on Influenza and Other Respiratory Virus Vaccines. Advisory Group on pulmonary function tests in relation to live influenza virus vaccines.

A multicentre study of the effects of influenza virus RIT 4050 (H3N2) in patients with chronic bronchitis was conducted by members of an MRC Committee. The results showed that RIT 4050 vaccine virus did not cause a deterioration in clinical or physiological status in these patients within the limitation of the relatively reproducible ventilatory tests which were employed. This conclusion applied equally to those who were inoculated and became infected and to those who failed to develop serological evidence of infection. The relatively high proportion of antibody-negative volunteers not infected by the inoculated virus raises doubts concerning the value of this method of immunization for patients at risk during influenza epidemics.