Role of influenza vaccine for healthy children in the US

Seasonal Influenza Vaccination Among Saudi Children: Parental Barriers and Willingness to Vaccinate Their Children in the Makkah Region

INTRODUCTION

The influenza virus produces everything from seasonal epidemics to unexpected pandemics, making its prevention and management a worldwide public health challenge. The main method to prevent and control seasonal influenza is vaccination. Children responded quite successfully to influenza vaccinations, particularly live vaccines. Despite the strong recommendations and effectiveness of seasonal influenza vaccinations in children, some parents still hesitate and refuse to give their children the shot.

OBJECTIVE

This study, given the importance of knowing the factors that contribute to parents' refusal of influenza vaccine, also aims to assess parental barriers and willingness to vaccinate their children in the Makkah region of Saudi Arabia.

METHODOLOGY

This is a descriptive cross-sectional study conducted among Saudi parents in the Makkah region. For data collection, an online survey was conducted between December 1, 2022, and February 11, 2023.

RESULTS

In total, 334 of the parents participated in our study. The result shows that there is a significant association between parents' gender and receiving the flu vaccine, with significantly more females (52.4%). Regarding the willingness to get the vaccine, the majority of the parents reported that they will get the vaccine and vaccinate their children, and the most common barrier that prevents parents from vaccinating their children is that they do not need it because they are healthy (21.48%). Furthermore, there is a strong relationship between educational level and knowledge about seasonal influenza vaccination; the majority of parents at each level of education have poor knowledge regarding influenza vaccines. In addition, nearly all of our participants (96.7%) believed the information provided by the Saudi Ministry of Health as well as the advice of their physicians.

CONCLUSION

This study highlights the need to increase awareness, educate the parents in the Makkah region about the importance of the influenza vaccine, and encourage them to vaccinate their children.

Pediatric influenza vaccination rates lower than previous estimates in the United States

BACKGROUND

Annually, pediatric influenza vaccination coverage estimates are ascertained from health surveys, such as the National Immunization Survey (NIS-Flu). From 2010 to 2017, vaccination coverage among children ranged from 51 to 59 %. Recognizing the limitations of national health survey data, we sought to describe temporal trends in pediatric influenza vaccination coverage, and demographic differences among a commercially insured large national cohort from 07/01/2010 to 06/30/2017.

METHODS

Influenza vaccination coverage was assessed among children (<18 years) with continuous enrollment in the de-identified Optum Clinformatics® Data Mart database, and from NIS-Flu. Time trends in vaccination coverage were assessed using Joinpoint regression, overall and stratified by age group, sex, and geographic region.

RESULTS

The average annual pediatric influenza vaccination coverage was 33.4 % in our study population versus 56.5 % reported from NIS-Flu during the same period (p-value < 0.0001). Vaccination coverage was highest in children 6 months-4-years old at 52.6 % (versus 68.8 % NIS-Flu, p-value < 0.0001), and lowest in the 13-17-year-old age group at 20.1 % (versus 42.8 % NIS-Flu, p-value < 0.0001). Vaccination coverage over time remained stable in our study population (average annual percent change 1.8 %, 95 % confidence interval [CI] -2.3 % to 6.0 %) versus significantly increasing by 2.8 % in NIS-Flu (95 % CI 0.3 % to 5.3 %).

CONCLUSIONS

Vaccination coverage in our commercially insured pediatric population was 51.4% lower than estimates from NIS-Flu during the same period, suggesting the need for more accurate vaccination coverage surveillance, which will also be critical in future COVID-19 vaccination efforts. Effective interventions are needed to increase pediatric influenza vaccination rates to the Healthy People 2020 target of 70%.

Identification of a novel compound targeting the nuclear export of influenza A virus nucleoprotein

Although antiviral drugs are available for the treatment of influenza infection, it is an urgent requirement to develop new antiviral drugs regarding the emergence of drug‐resistant viruses. The nucleoprotein (NP) is conserved among all influenza A viruses (IAVs) and has no cellular equivalent. Therefore, NP is an ideal target for the development of new IAV inhibitors. In this study, we identified a novel anti‐influenza compound, ZBMD‐1, from a library of 20,000 compounds using cell‐based influenza A infection assays. We found that ZBMD‐1 inhibited the replication of H1N1 and H3N2 influenza A virus strains in vitro, with an IC₅₀ ranging from 0.41–1.14 μM. Furthermore, ZBMD‐1 inhibited the polymerase activity and specifically impaired the nuclear export of NP. Further investigation indicated that ZBMD‐1 binds to the nuclear export signal 3 (NES3) domain and the dimer interface of the NP pocket. ZBMD‐1 also protected mice that were challenged with lethal doses of A/PR/8/1934 (H1N1) virus, effectively relieving lung histopathology changes, as well as strongly inhibiting the expression of pro‐inflammatory cytokines/chemokines, without inducing toxicity effects in mice. These results suggest that ZBMD‐1 is a promising anti‐influenza compound which can be further investigated as a useful strategy against IAVs in the future.

Verdinexor, a novel selective inhibitor of nuclear export, reduces influenza a virus replication in vitro and in vivo

Influenza is a global health concern, causing death, morbidity, and economic losses. Chemotherapeutics that target influenza virus are available; however, rapid emergence of drug-resistant strains is common. Therapeutic targeting of host proteins hijacked by influenza virus to facilitate replication is an antiviral strategy to reduce the development of drug resistance. Nuclear export of influenza virus ribonucleoprotein (vRNP) from infected cells has been shown to be mediated by exportin 1 (XPO1) interaction with viral nuclear export protein tethered to vRNP. RNA interference screening has identified XPO1 as a host proinfluenza factor where XPO1 silencing results in reduced influenza virus replication. The Streptomyces metabolite XPO1 inhibitor leptomycin B (LMB) has been shown to limit influenza virus replication in vitro; however, LMB is toxic in vivo, which makes it unsuitable for therapeutic use. In this study, we tested the anti-influenza virus activity of a new class of orally available small-molecule selective inhibitors of nuclear export, specifically, the XPO1 antagonist KPT-335 (verdinexor). Verdinexor was shown to potently and selectively inhibit vRNP export and effectively inhibited the replication of various influenza virus A and B strains in vitro, including pandemic H1N1 virus, highly pathogenic H5N1 avian influenza virus, and the recently emerged H7N9 strain. In vivo, prophylactic and therapeutic administration of verdinexor protected mice against disease pathology following a challenge with influenza virus A/California/04/09 or A/Philippines/2/82-X79, as well as reduced lung viral loads and proinflammatory cytokine expression, while having minimal toxicity. These studies show that verdinexor acts as a novel anti-influenza virus therapeutic agent.

IMPORTANCE

Antiviral drugs represent important means of influenza virus control. However, substantial resistance to currently approved influenza therapeutic drugs has developed. New antiviral approaches are required to address drug resistance and reduce the burden of influenza virus-related disease. This study addressed critical preclinical studies for the development of verdinexor (KPT-335) as a novel antiviral drug. Verdinexor blocks progeny influenza virus genome nuclear export, thus effectively inhibiting virus replication. Verdinexor was found to limit the replication of various strains of influenza A and B viruses, including a pandemic H1N1 influenza virus strain, a highly pathogenic H5N1 avian influenza virus strain, and a recently emerging H7N9 influenza virus strain. Importantly, oral verdinexor treatments, given prophylactically or therapeutically, were efficacious in limiting lung virus burdens in influenza virus-infected mice, in addition to limiting lung proinflammatory cytokine expression, pathology, and death. Thus, this study demonstrated that verdinexor is efficacious against influenza virus infection in vitro and in vivo.

Virus-vectored influenza virus vaccines

Despite the availability of an inactivated vaccine that has been licensed for >50 years, the influenza virus continues to cause morbidity and mortality worldwide. Constant evolution of circulating influenza virus strains and the emergence of new strains diminishes the effectiveness of annual vaccines that rely on a match with circulating influenza strains. Thus, there is a continued need for new, efficacious vaccines conferring cross-clade protection to avoid the need for biannual reformulation of seasonal influenza vaccines. Recombinant virus-vectored vaccines are an appealing alternative to classical inactivated vaccines because virus vectors enable native expression of influenza antigens, even from virulent influenza viruses, while expressed in the context of the vector that can improve immunogenicity. In addition, a vectored vaccine often enables delivery of the vaccine to sites of inductive immunity such as the respiratory tract enabling protection from influenza virus infection. Moreover, the ability to readily manipulate virus vectors to produce novel influenza vaccines may provide the quickest path toward a universal vaccine protecting against all influenza viruses. This review will discuss experimental virus-vectored vaccines for use in humans, comparing them to licensed vaccines and the hurdles faced for licensure of these next-generation influenza virus vaccines.

Seasonal influenza and vaccine herd effect

The seasonal influenza vaccine programs in many regions aimed to protect most vulnerable population, but current trivalent influenza vaccine does not provide sufficient effectiveness among people under high risk for severe outcome of the influenza. The vaccine herd effect (VHE) is the extra protection of non-immune high risk persons, with increase of immunity among vaccinated healthier persons which prevents circulation of influenza in the community. Accumulating evidences are supporting the immunization of extended population with regard to the VHE.

Enhancement of the immunogenicity and protective efficacy of a mucosal influenza subunit vaccine by the saponin adjuvant GPI-0100

Identification of safe and effective adjuvants remains an urgent need for the development of inactivated influenza vaccines for mucosal administration. Here, we used a murine challenge model to evaluate the adjuvant activity of GPI-0100, a saponin-derived adjuvant, on influenza subunit vaccine administered via the intranasal or the intrapulmonary route. Balb/c mice were immunized with 1 µg A/PR/8 (H1N1) subunit antigen alone or in combination with varying doses of GPI-0100. The addition of GPI-0100 was required for induction of mucosal and systemic antibody responses to intranasally administered influenza vaccine and significantly enhanced the immunogenicity of vaccine administered via the intrapulmonary route. Remarkably, GPI-0100-adjuvanted influenza vaccine given at a low dose of 2×1 µg either in the nares or directly into the lungs provided complete protection against homologous influenza virus infection.

Nasal vaccine innovation

The current vaccine market is gaining momentum in the development of alternative administration routes namely intranasal, oral, topical, pulmonary, vaginal, and rectal; the nasal route offers the most promising opportunity for vaccine administration. It can enhance convenience, safety, elicit both local and systemic immune responses; thus potentially provide protection from pathogens at the site of entry. Nasal vaccine innovation comes with both opportunities and challenges. The innovative strategies used by industry and researchers to overcome the hurdles are discussed in this article: these include live-attenuated vaccines, adjuvants, mucoadhesives, particulate delivery systems, virus-like particles, vaccine manufacture, challenges of regulatory authorities, and the nasal vaccine impact on market potential. Critical issues for effective nasal vaccination are the antigen-retention period that enables its interaction with the lymphatic system and choice of an adjuvant that is nontoxic and induces the required immune response. Co-adjuvanting by means of a mucoadhesive technology addresses some of these issues. ChiSys(®), a natural bioadhesive with proven intranasal safety profile, has already demonstrated efficacy for several nasally delivered vaccines including norovirus. With the looming threat of a pandemic, alternatives such as intranasal vaccination will ultimately facilitate greater public compliance and rapid mass global vaccination.

Association between patient age and influenza A subtype during influenza outbreaks

The distribution of influenza A subtypes was studied in specimens recovered from patients in long-term care facility (LTCF) outbreaks and in non-LTCF outbreaks in Alberta, Canada, for 3 years before the influenza pandemic of 2009. We found that H3 but not H1 was associated with infection in older adults. Therefore, H3 was more commonly found than H1 in outbreaks in LTCFs.

Adverse events associated with intranasal influenza vaccine in the United States

METHODS

The goal of this review was to analyze the post-vaccination adverse effects associated with Live Attenuated Influenza Vaccine (LAIV) compared to those of the Injectable Trivalent Inactivated Vaccine (TIV) in patients with egg allergy and asthma. PubMed, Ovid, and Google searches were conducted. Searched articles relating to allergic reactions, asthma or food allergy, and LAIV were reviewed.

RESULTS

Similar or superior efficacy of LAIV compared to TIV was reported by various studies. Respiratory symptoms were the most common adverse events following both vaccinations. Although no evidence was found of a direct causal relationship between intranasal influenza vaccine and anaphylaxis due to egg allergy, a number of cases of anaphylaxis were reported. To date, there are no studies directly comparing the frequency of anaphylactic reactions between the two vaccines.

CONCLUSIONS

The safety of LAIV in individuals with unstable asthma and egg allergy has not been established and it should be avoided in these populations. For patients with unstable asthma, TIV should remain the therapy of choice.

Animal models for evaluation of influenza vaccines

Influenza viruses are emerging and re-emerging viruses that cause worldwide epidemics and pandemics. Despite substantial knowledge of the mechanisms of infection and immunity, only modest progress has been made in human influenza vaccine development. The rational basis for influenza vaccine development originates in animal models that have helped us to understand influenza species barriers, virus-host interactions, factors that affect transmission, disease pathogenesis, and disease intervention strategies. As influenza evolution can surmount species barriers and disease intervention strategies that include vaccines, our need for appropriate animal models and potentially new host species will evolve to meet these adaptive challenges. This chapter discusses animal models for evaluating vaccines and discusses the challenges and strengths of these models.

Vaccines for Pandemic Influenza. The History of our Current Vaccines, their Limitations and the Requirements to Deal with a Pandemic Threat

Fears of a potential pandemic due to A(H5N1) viruses have focussed new attention on our current vaccines, their shortcomings, and concerns regarding global vaccine supply in a pandemic. The bulk of current vaccines are inactivated split virus vaccines produced from egggrown virus and have only modest improvements compared with those first introduced over 60 years ago. Splitting, which was introduced some years ago to reduce reactogenicity, also reduces the immunogenicity of vaccines in immunologically naïve recipients. The A(H5N1) viruses have been found poorly immunogenic and present other challenges for vaccine producers which further exacerbate an already limited global production capacity. There have been some recent improvements in vaccine production methods and improvements to immunogenicity by the development of new adjuvants, however, these still fall short of providing timely supplies of vaccine for all in the face of a pandemic. New approaches to influenza vaccines which might fulfil the demands of a pandemic situation are under evaluation, however, these remain some distance from clinical reality and face significant regulatory hurdles. Key words: Adjuvant, Antigen, Cell-culture, Immune response, Immunogenicity, Influenza A(H5N1), Split vaccine

The impact of influenza on working days lost: a review of the literature

Seasonal influenza is a prevalent and highly contagious acute respiratory disease that, year on year, results in increased morbidity and mortality on a global scale. Because of the widespread and debilitating nature of the disease, annual influenza epidemics result in substantial workplace absenteeism, and the associated cost of lost productivity is a significant component of the substantial financial burden of the disease to society. The objective of this review was to identify studies that had attempted to quantify the impact of influenza upon otherwise healthy adults in terms of working days lost associated with an episode of influenza.Studies were included if they reported estimates of working days lost due to clinical, physician and/or self-diagnosis in adult patients or their dependants, or where this figure could be estimated from the data. Searches were conducted in MEDLINE, EMBASE, BIOSIS and the Cochrane Collaboration for articles published since 1995 in English, French or German. Of the 289 papers identified in the search, 28 (9.7%) met the inclusion criteria. The studies, involving study sites in North America, Western Europe, Asia and Australia, were categorized into three groups: (i) those reporting influenza diagnoses confirmed by laboratory testing, i.e. studies where influenza was the unambiguous cause of the working days lost (n = 7 studies reported in ten publications); (ii) those where influenza was confirmed by a physician without an accompanying laboratory test (n = 4 studies); and (iii) those where influenza was self-reported by study participants (n = 14 studies). Qualitative reporting of results was performed because of the large degree of heterogeneity observed between studies, potentially complicating the interpretation of any meta-analysis.The results from studies involving a laboratory-confirmed influenza diagnosis suggested that the mean number of working days lost ranged between 1.5 and 4.9 days per episode. Those papers that detailed working days lost per episode following physician diagnosis of influenza reported a range of 3.7-5.9 days per episode. Finally, estimates from papers reporting working days lost per episode of self-reported influenza ranged from <1 day to 4.3 days per episode.Influenza imposes a significant burden on society, and this review highlights the significant economic impact it causes, i.e. the loss of productivity caused by both absenteeism and by staff functioning at reduced capacity even after they have returned to work. A number of prophylaxis and treatment options exist for influenza and should be given serious consideration in an attempt to reduce the economic burden on society.

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

BACKGROUND & AIMS

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Comparison of the influenza virus-specific effector and memory B-cell responses to immunization of children and adults with live attenuated or inactivated influenza virus vaccines

Cellular immune responses to influenza virus infection and influenza virus vaccination have not been rigorously characterized. We quantified the effector and memory B-cell responses in children and adults after administration of either live attenuated (LAIV) or inactivated (TIV) influenza virus vaccines and compared these to antibody responses. Peripheral blood mononuclear cells were collected at days 0, 7 to 12, and 27 to 42 after immunization of younger children (6 months to 4 years old), older children (5 to 9 years old), and adults. Influenza virus-specific effector immunoglobulin A (IgA) and IgG circulating antibody-secreting cells (ASC) and stimulated memory B cells were detected using an enzyme-linked immunospot assay. Circulating influenza virus-specific IgG and IgA ASC were detected 7 to 12 days after TIV and after LAIV immunization. Seventy-nine percent or more of adults and older children had demonstrable IgG ASC responses, while IgA ASC responses were detected in 29 to 53% of the subjects. The IgG ASC response rate to LAIV immunization in adults was significantly higher than the response rate measured by standard serum antibody assays (26.3% and 15.8% by neutralization and hemagglutination inhibition assays, respectively). IgG ASC and serum antibody responses were relatively low in the younger children compared to older children and adults. TIV, but not LAIV, significantly increased the percentage of circulating influenza virus-specific memory B cells detected at 27 to 42 days after immunization in children and adults. In conclusion, although both influenza vaccines are effective, we found significant differences in the B-cell and antibody responses elicited after LAIV or TIV immunization in adults and older children and between young children and older age groups.

Alternative routes of influenza vaccine delivery

The global emergence of virulent avian influenza and the concomitant raised threat of an influenza pandemic has increased interest in the development of improved influenza vaccines. Whereas conventional influenza vaccines are delivered by parenteral injection, an intranasal influenza vaccine has been marketed since 2003. Many other technologies are in development for intranasal, oral, epidermal and topical influenza vaccines. This editorial summarises the advances in clinical development of technologies for needle-free influenza vaccine delivery.