Influenza Vaccine In Children Research Articles

‘It's not for the children's sake’: A qualitative inquiry into the barriers and facilitators underlying parents' decision-making for vaccinating children against influenza in Denmark

Recently, the Danish Health Authority began recommending vaccinating children aged 2–6 years against seasonal influenza, underscoring the pivotal role of children in its transmission dynamics within the wider population and the need to protect vulnerable population groups after COVID-19. Under a third followed the recommendation. For the routine Danish childhood vaccine program coverage is usually well above 90%.Through a qualitative in-depth study with 28 key informants during the 2022/2023 influenza season, we investigated the barriers and facilitators of parents' decision-making for vaccinating their children against influenza. We found that parents' decision-making was influenced by a range of factors that present barriers or facilitators at the individual or collective levels, depending on personal antecedents and family situations. We also gained insights on how COVID-19 mass vaccination shaped parents’ attitudes and awareness toward influenza vaccination, explaining why many parents who fully complied with the COVID-19 recommendations elected to opt out of influenza.The implications of these findings extend beyond the concrete context of parent's decision-making regarding influenza vaccination, contributing to our understanding of vaccine confidence in at least two ways. First, the limited public controversy regarding childhood influenza vaccination allows for a perspective onto low vaccine uptake that does not resort to the usual framing of a well-defined “crisis”. Second, the interaction between COVID-19 vaccination and the childhood influenza vaccination reveals how the massive pressure on parents to vaccinate themselves and their children against COVID-19 contributed to an erosion of vaccine confidence in general.

Influenza antibody breadth and effector functions are immune correlates from acquisition of pandemic infection of children

Cross-reactive antibodies with Fc receptor (FcR) effector functions may mitigate pandemic virus impact in the absence of neutralizing antibodies. In this exploratory study, we use serum from a randomized placebo-controlled trial of seasonal trivalent influenza vaccination in children (NCT00792051) conducted at the onset of the 2009 H1N1 pandemic (pH1N1) and monitored for infection. We found that seasonal vaccination increases pH1N1 specific antibodies and FcR effector functions. Furthermore, prospective baseline antibody profiles after seasonal vaccination, prior to pH1N1 infection, show that unvaccinated uninfected children have elevated ADCC effector function, FcγR3a and FcγR2a binding antibodies to multiple pH1N1 proteins, past seasonal and avian (H5, H7 and H9) strains. Whereas, children that became pH1N1 infected after seasonal vaccination have antibodies focussed to seasonal strains without FcR functions, and greater aggregated HA-specific profiles for IgM and IgG3. Modeling to predict infection susceptibility, ranked baseline hemagglutination antibody inhibition as the highest contributor to lack of pH1N1 infection, in combination with features that include pH1-IgG1, H1-stem responses and FcR binding to seasonal vaccine and pH1 proteins. Thus, seasonal vaccination can have benefits against pandemic influenza viruses, and some children already have broadly reactive antibodies with Fc potential without vaccination and may be considered ‘elite influenza controllers’.

Estimating averted illnesses from influenza vaccination for children and pregnant women – El Salvador, Panama, and Peru, 2011–2018

BackgroundEstimating the burden of disease averted by vaccination can assist policymakers to implement, adjust, and communicate the value of vaccination programs. Demonstrating the use of a newly available modeling tool, we estimated the burden of influenza illnesses averted by seasonal influenza vaccination in El Salvador, Panama, and Peru during 2011–2017 among two influenza vaccine target populations: children aged 6–23 months and pregnant women. MethodsWe derived model inputs, including incidence, vaccine coverage, vaccine effectiveness, and multipliers from publicly available country-level influenza surveillance data and cohort studies. We also estimated changes in illnesses averted when countries’ vaccine coverage was achieved using four different vaccine deployment strategies. ResultsAmong children aged 6–23 months, influenza vaccination averted an estimated cumulative 2,161 hospitalizations, 81,907 medically-attended illnesses, and 126,987 overall illnesses during the study period, with a prevented fraction ranging from 0.3 % to 12.5 %. Among pregnant women, influenza vaccination averted an estimated cumulative 173 hospitalizations, 6,122 medically attended illnesses, and 16,412 overall illnesses, with a prevented fraction ranging from 0.2 % to 10.9 %. Compared to an influenza vaccine campaign with equal vaccine distribution during March—June, scenarios in which total cumulative coverage was achieved in March and April consistently resulted in the greatest increase in averted illness (23 %-3,129 % increase among young children and 22 %-3,260 % increase among pregnant women). DiscussionInfluenza vaccination campaigns in El Salvador, Panama, and Peru conducted between 2011 and 2018 prevented hundreds to thousands of influenza-associated hospitalizations and illnesses in young children and pregnant women. Existing vaccination programs could prevent additional illnesses, using the same number of vaccines, by achieving the highest possible coverage within the first two months of an influenza vaccine campaign.

Unlocking the Power of Influenza Vaccines for Pediatric Population: A Narrative Review.

The flu, often known as influenza, is a dangerous public health hazard for the pediatric population. Immunization is essential for decreasing the burden of the disease and avoiding complications related to influenza. However, the immunogenicity, efficacy, and safety of different influenza vaccines in children warrant careful evaluation. The purpose of this narrative review is to give a summary of the existing literature on the immunogenicity, efficacy, and safety of several vaccinations against influenza viruses in children. The review incorporates evidence from a range of studies focusing on the outcomes of interest. Immunogenicity studies have shown that influenza vaccines induce a robust immune response in children, primarily through neutralizing antibodies' formation. However, variations in vaccine composition influence the duration and magnitude of immune responses. Safety is a crucial consideration in pediatric vaccination. In children, influenza vaccinations have generally shown a high safety profile, with mild and temporary side effects being the most common. Vaccinations against influenza have shown a modest level of efficacy in avoiding hospitalizations linked to influenza, laboratory-confirmed influenza infections, and serious consequences in children. Live attenuated vaccines have shown higher effectiveness against matched strains compared to inactivated vaccines. In conclusion, this narrative review highlights that receiving influenza vaccination in children aged six to 47 months is very important. While different vaccines exhibit varying immunogenicity, safety profiles, and effectiveness, they all contribute to reducing the burden of influenza among children. Future research should focus on optimizing vaccine strategies, improving vaccine coverage, and evaluating long-term protection.

Factors Influencing Childhood Influenza Vaccination: A Systematic Review.

Childhood influenza vaccination coverage remains low in lower/middle-income countries. This systematic review aims to identify influencing factors around childhood influenza vaccination. A systematic literature review was conducted and included empirical studies with original data that investigated factors influencing childhood influenza vaccination. We searched MEDLINE, Web of Science, EMBASE, CINAHL Plus, Global Health, PsycINFO, and two Chinese databases, China Knowledge Resource Integrated Database and Chongqing VIP, using a combination of the key terms 'childhood', 'influenza', 'vaccination', and related syntax for all peer-reviewed publications published before December 2019. Thirty studies were included in the analysis. Childhood influenza vaccination was positively associated with caregivers' knowledge of influenza vaccine, positive vaccine attitudes, self-efficacy, perceived susceptibility and severity of influenza, believing in the efficacy of influenza vaccine, the worry of getting sick, healthcare workers' recommendations, and previous influenza vaccination experiences. Barriers included the fear of safety and side effects of the vaccine, as well as poor access to vaccination service. To improve childhood influenza vaccine uptake, health education is necessary to address caregivers' lack of confidence on vaccine safety. Future studies are needed to investigate influencing factors around healthcare workers' vaccination recommendation behaviors and the impact of contextual factors on public vaccination behaviors.

Optimal timing of influenza vaccination in young children: population based cohort study

ObjectiveTo assess optimal timing of influenza vaccination in young children.DesignPopulation based cohort study.SettingUnited States.ParticipantsCommercially insured children aged 2-5 years who were vaccinated against influenza during 2011-18.Main outcome measureRates of diagnosis...

Cost-effectiveness analysis of cell-based versus egg-based quadrivalent influenza vaccines in the pediatric population in Taiwan.

Cell-based influenza vaccines avoid egg-adaptive mutations, potentially improving vaccine effectiveness. We assessed the one-season cost-effectiveness of cell-based quadrivalent influenza vaccine (QIVc) against that of egg-derived quadrivalent influenza vaccines (QIVe) in children (6 months to 17 years of age) from payer and societal perspectives in Taiwan using an age-stratified static model. Base case and high egg adaptation scenarios were assessed. Deterministic and probabilistic sensitivity analyses were performed. The incremental cost-effectiveness ratio (ICER) threshold in Taiwan was assumed to be USD 99 177/quality-adjusted life year (QALY). Compared to QIVe, QIVc would prevent 15 665 influenza cases, 2244 complicated cases, and 259 hospitalizations per year. The base case ICER was USD 68 298/QALY and USD 40 085/QALY from the payer and societal perspective, respectively. In the high egg adaptation scenario, the ICER was USD 45 782/QALY from the payer's perspective and USD 17 489/QALY from the societal perspective. Deterministic sensitivity analyses indicated that infection incidence rate, vaccination coverage, and prevalence of the A/H3N2 strain were the main drivers of ICER. In conclusion, switching the immunization strategy from QIVe to QIVc is predicted to reduce the influenza-associated disease burden and be cost-effective for the pediatric population in Taiwan. The potential benefits of QIVc would be even higher during influenza seasons with high levels of egg adaptation.

Modelling the population-level benefits and cost-effectiveness of cell-based quadrivalent influenza vaccine for children and adolescents aged 6 months to 17 years in the US

ABSTRACT Background Cell-based quadrivalent influenza vaccines (QIVc) can increase effectiveness against seasonal influenza by avoiding mismatch from egg adaption of vaccine viruses. This study evaluates the population-level cost-effectiveness and impacts on health outcomes of QIVc versus an egg-based vaccine (QIVe) in children aged 6 months to 17 years in the US. Research Design and Methods A dynamic age-structured susceptible-exposed-infected-recovered model was used to simulate influenza transmission in low and high incidence seasons for two scenarios: 1. QIVe for 6 months–17 year-olds, QIVc for 18–64 year-olds, and adjuvanted QIV (aQIV) for ≥ 65 year-olds, and 2. QIVc for 6 months–64 year-olds, and aQIV for ≥ 65 year-olds. Probabilistic sensitivity analysis was performed to account for uncertainty in parameter estimates. Cost-effectiveness was evaluated as incremental cost-effectiveness ratios (ICERs). Results Extension of QIVc to children resulted in 3–4% reductions in cases (1,656,271), hospitalizations (16,688), and deaths (2,126) at a population level in a high incidence season, and 65% reductions (cases: 2,856,384; hospitalizations: 31667; deaths: 4,163) in a low incidence season. Use of QIVc would be cost-saving, with ICERs of -$16,427/QALY and -$8,100/QALY from a payer perspective and -$22,669/QALY and -$15,015/QALY from a societal perspective, for low and high incidence seasons respectively. Cost savings were estimated at approximately $468 million and $1.366 billion for high and low incidence seasons, respectively. Conclusion Use of QIVc instead of QIVe in children > 6 months of age in the US would reduce the disease burden and be cost-saving from both a payer and societal perspective.

[Feasibility analysis of adult vaccination in children's vaccination clinic in Shandong Province].

Objective: To investigate the operation of children's vaccination clinics in Shandong Province, simulate the efficiency of vaccination capacity utilization, and explore the feasibility of carrying out adult vaccination in children's vaccination clinics. Methods: Using the extreme hypothesis method to determine the maximum vaccination capacity of children's vaccination clinics. Based on on-site surveys, population, and vaccination rate data, simulation parameters were determined, and the simulation method was used to simulate the utilization efficiency of vaccination capacity in different scenarios of children's vaccination clinics. Results: There were 2 654 children's vaccination clinics by the end of 2021 in Shandong province. There was (6.93±4.02) staff per vaccination clinic, with an average opening day of (4.16±2.19) days per week. In the scenario of only vaccinating children, the utilization efficiency of vaccination capacity during the non-influenza vaccination season was only 30.74% and 14.07% in urban and rural vaccination clinics, respectively. During the influenza vaccination season, the utilization efficiency of the vaccination capacity of urban vaccination clinics reached 49.26% when the child influenza vaccination rate reached 20%. In the scenario of simultaneous vaccination of children and adults, the utilization efficiency of vaccination capacity during the non-influenza vaccination season was 41.48% and 18.52% in urban and rural vaccination clinics, respectively. During the influenza vaccination season, the utilization efficiency of vaccination capacity in urban vaccination clinics reached 51.47% when the influenza vaccination rate of the entire population reached 3%. The utilization efficiency of vaccination capacity in rural vaccination clinics reached 52.44% when the influenza vaccination rate of the entire population reached 20%. Conclusion: The accessibility of children's vaccination is good in Shandong province, and the utilization efficiency of vaccination capacity can meet the current vaccination needs of children and adults. The vaccination capacity in urban areas needs to be strengthened to meet the growing vaccination needs of children and adults in the future.

Parental Concerns and Attitudes Regarding Influenza Vaccination of Children with Asthma During the COVID‐19 Pandemic

Parental Concerns and Attitudes Regarding Influenza Vaccination of Children with Asthma During the COVID‐19 Pandemic

1719. Duration of antibodies after immunization with the quadrivalent influenza vaccine in children after hematopoietic stem cell transplantation or chemotherapy compared to healthy children

Abstract Background Children that have undergone hematopoietic stem cell transplantation (HSCT) are at a higher risk for severe influenza. The purpose of this study was to compare the duration of antibodies after immunization with the quadrivalent influenza vaccine (QIV) in children after hematopoietic stem cell transplantation or chemotherapy compared to healthy children. Methods This was a prospective study of children below 18 years old that received the QIV influenza vaccine during the 2021-2022 influenza vaccination season. Children were divided into 3 groups as follows: a) post-HSCT, b) post-chemotherapy, and c) immunocompetent children as a healthy control. Blood samples were taken immediately before immunization, at 1 month, 3 months, 6 months, and 12 months after immunization. Hemagglutination Inhibition (HI) assays were performed. Seropositive rate was defined by the percentage of patients with HI titer ≥1:40. Seroconversion rate (SCR) was defined as follows: 1) in patients with a pre-vaccination HI titer < 1:10, rise in post-vaccination HI titers ≥1:40, or in patients with pre-vaccination HI titers ≥1:40, a 4-fold increase. Results A total of 60 children were included in the preliminary analyses, n=20 in each of the three groups. The SPR at post-vaccination 1 month for both A/H1N1 and H3N2 exceeded 80% in all three groups. The SPR remained above 60% at 3 months post-immunization for both A antigens. However, by 6 months post-vaccination, the SPR dropped to 50% in the post-chemotherapy group for the A/H1N1 antigen, and the geometric mean titers (GMTs) were 26.39. For B/Victoria and B/Yamagata, the SPR was below 40% in the post-HSCT and post chemotherapy group at 1 months and below 20% by 3 months. The GMTs were also below 1:40 for both antigens. In the normal control group, the SPR for B/Victoria was 50% at 1 months and 45% at 3 months post-immunization, and for B/Yamagata, 50% at 1 months and 55% at 3 months post-immunization. However, the GMTs were below 1:40 by 3 months post-immunization. Conclusion For A/H1N1, the SPR and GMTs at 6 months in the post-chemotherapy was low. In both the post-HSCT and chemotherapy group, HI titers were low for both B antigens at 1-month post-vaccination, and GMTs showed < 1:40. B antigens contained within QIV need to illicit better protection against Influenza in children. Disclosures All Authors: No reported disclosures

Influenza vaccination in children with pulmonary disease during the COVID-19 pandemic

IntroductionInfluenza is associated with considerable respiratory morbidity and mortality. Healthcare authorities recommend immunization of all children as vaccinations protect vulnerable populations, minimize influenza triggered asthma attacks, and reduced the burden of respiratory illnesses during the SARS-CoV-2 pandemic. Medical professionals should counsel parents of children with chronic lung disease to receive annual influenza vaccinations as part of supportive care. We aimed to describe adherence to influenza vaccination in respiratory patients and identify potential reasons for non-vaccination. MethodsThis study included questionnaires reviewing personal experience and beliefs regarding influenza vaccination, provided by parents of patients who visited the Pediatric Pulmonary Institute at Schneider Children’s Medical Center with their children, during March-August 2021. ResultsOf 198 parents who completed our questionnaire, 114 (57.3 %) vaccinated their children against influenza during that year. Average age was 6.9 ± 4.5 years. Demographic data were similar between the vaccinated and unvaccinated groups. Influenza vaccination rates differed significantly between parents who received an explanation from their primary physician and those who did not (65.4 % vs. 43.7 %, respectfully, p = 0.003), and parents who received explanations from a pulmonary specialist and those who did not (77.3 % vs. 48.8 %, respectively, p = 0.004). The combined recommendation of a primary physician and pulmonologist translated to a significantly higher vaccination rate among those who received such recommendations, as compared to those who did not (p < 0.001). Parents who believed in vaccine efficacy and safety were more likely to vaccinate their children (p < 0.001). Factors significantly affecting the decision of the parents to have their child vaccinated were their knowledge, beliefs, and conceptions about the vaccine. ConclusionsPediatric respiratory patients’ influenza vaccination rate was 57 %. Major factors encouraging vaccination were correct parental knowledge and receiving recommendations from their primary physician\\pulmonologist. This emphasizes the need for providing patients with information, by first explaining the vaccine’s importance to physicians.

Determinants of parental self-reported uptake of influenza vaccination in preschool children during the COVID-19 pandemic

ABSTRACT In China, the coverage rate of influenza vaccination among the general population is significantly lower than that of high-income countries, with only 2.46% of the population vaccinated. Preschool-aged children are particularly susceptible to influenza viruses, yet the factors that influence parents’ willingness to vaccinate their children are not well understood. To address this research gap, we developed a theoretical model grounded in the Unified Theory of Acceptance and Use of Technology (UTAUT), which explores six key factors influencing parental self-reported uptake of influenza vaccination in preschool children: performance expectancy, effort expectancy, social influence, facilitating conditions, knowledge, and behavioral intention. We collected data from 872 parents of children in five major cities in China and employed structural equation modeling to examine the significance of the theoretical model and explore the potential moderating effects of demographic variables on path relationships. Our analysis revealed that several positive factors influenced parents’ intention of influenza vaccination for preschool children, including effort expectancy (β = 0.38), social influence (β = 0.17), and knowledge (β = 0.52). Facilitating conditions (β = 0.34), knowledge (β = 0.40), and behavioral intention (β = 0.34) were found to be associated with self-reported uptake. Furthermore, we observed significant moderating effects of the child’s gender and age, as well as the guardian’s category and income, on the theoretical models. Parents’ willingness to vaccinate preschool children against influenza is influenced by both psychological and demographic variables. Further studies are needed to determine if these relationships persist over time and across different regions.

Influenza vaccination in Western Australian children: Exploring the health benefits and cost savings of increased vaccine coverage in children

IntroductionTo assess potential benefits and direct healthcare cost savings with expansion of an existing childhood influenza immunisation program, we developed a dynamic transmission model for the state of Western Australia, evaluating increasing coverage in children < 5 years and routinely immunising school-aged children. MethodsA deterministic compartmental Susceptible-Exposed-Infectious-Recovered age-stratified transmission model was developed and calibrated using laboratory-notification and hospitalisation data. Base case vaccine coverage estimates were derived from 2019 data and tested under moderate, low and high vaccine effectiveness settings. The impact of increased coverage on the burden of influenza, influenza-associated presentations and net costs were assessed using the transmission model and estimated health utilisation costs. ResultsUnder base case vaccine coverage and moderate vaccine effectiveness settings, 225,460 influenza cases are expected annually across all ages. Direct healthcare costs of influenza were estimated to be A$27,608,286 per annum, dominated by hospital costs. Net cost savings of >$A1.5 million dollars were observed for every 10 % increase in vaccine coverage in children < 5 years. Additional benefits were observed by including primary school age children (5–11 years) in the funded influenza vaccination program - a reduction in cases, presentations, hospitalisations and approximately $A4 million net costs savings were observed for every 10 % increase in coverage. The further addition of older children (12–17 years) resulted in only moderate additional net cost savings figures, compared with a 5–11year-old program alone. Net costs savings were predominantly derived by a reduction in influenza-associated hospitalisation in adults. ConclusionsAny increase in influenza vaccine coverage in children < 5 years, above a base case of 50 % coverage resulted in a substantive reduction in influenza cases, presentations, hospitalisations and net costs when applied to the West Australian population. However, the most impactful pediatric program, from both a disease prevention and costs perspective, would be one that increased vaccination coverage among primary-school aged children.

Vaccine Effectiveness of Cell-Based Quadrivalent Influenza Vaccine in Children: A Narrative Review.

Cell-based manufacturing of seasonal influenza vaccines eliminates the risk of egg-adaptation of candidate vaccine viruses, potentially increasing vaccine effectiveness (VE). We present an overview of published data reporting the VE and cost-effectiveness of a cell-based quadrivalent influenza vaccine (QIVc) in preventing influenza-related outcomes in the pediatric population. We identified 16 clinical studies that included data on the VE of a QIVc or the relative VE (rVE) of a QIVc versus an egg-based QIV (QIVe) in children and/or adolescents, 11 of which presented estimates specifically for the pediatric age group. Of these, two studies reported rVE against hospitalizations. Point estimates of rVE varied from 2.1% to 33.0%, with studies reporting significant benefits of using a QIVc against influenza-related, pneumonia, asthma, and all-cause hospitalization. Four studies reported rVE against influenza-related medical encounters, with point estimates against non-strain specific encounters ranging from 3.9% to 18.8% across seasons. One study evaluated rVE against any influenza, with variable results by strain. The other four studies presented VE data against laboratory-confirmed influenza. Three health economics studies focusing on a pediatric population also found the use of QIVc to be cost-effective or cost-saving. Overall, using a QIVc is effective in pediatric patients, with evidence of incremental benefits over using a QIVe in preventing hospitalizations and influenza-related medical encounters in nearly all published studies.

Cost-effectiveness of seasonal influenza vaccination of children in China: a modeling analysis

BackgroundChina has a high burden of influenza-associated illness among children. We aimed to evaluate the cost-effectiveness of introducing government-funded influenza vaccination to children in China (fully-funded policy) compared with the status quo (self-paid policy).MethodsA decision tree model was developed to calculate the economic and health outcomes, from a societal perspective, using national- and provincial-level data. The incremental cost-effectiveness ratio (ICER) [incremental costs per quality-adjusted life year (QALY) gained] was used to compare the fully-funded policy with the self-paid policy under the willingness-to-pay threshold equivalent to national and provincial GDP per capita. Sensitivity analyses were performed and various scenarios were explored based on real-world conditions, including incorporating indirect effect into the analysis.ResultsCompared to the self-paid policy, implementation of a fully-funded policy could prevent 1,444,768 [95% uncertainty range (UR): 1,203,446–1,719,761] symptomatic cases, 92,110 (95% UR: 66,953–122,226) influenza-related hospitalizations, and 6494 (95% UR: 4590–8962) influenza-related death per season. The fully-funded policy was cost-effective nationally (7964 USD per QALY gained) and provincially for 13 of 31 provincial-level administrative divisions (PLADs). The probability of a funded vaccination policy being cost-effective was 56.5% nationally, and the probability in 9 of 31 PLADs was above 75%. The result was most sensitive to the symptomatic influenza rate among children under 5 years [ICER ranging from − 25,612 (cost-saving) to 14,532 USD per QALY gained]. The ICER of the fully-funded policy was substantially lower (becoming cost-saving) if the indirect effects of vaccination were considered.ConclusionsIntroducing a government-funded influenza policy for children is cost-effective in China nationally and in many PLADs. PLADs with high symptomatic influenza rate and influenza-associated mortality would benefit the most from a government-funded influenza vaccination program.

No association between inactivated influenza vaccination and influenza viral load at diagnosis among young Japanese children: An observational study of the 2013/2014 through 2017/2018 influenza seasons.

The association between inactivated influenza vaccination and viral load in young children remains unclear. During the 2013/2014 to 2017/2018 influenza seasons in Japan, children under 6years of age with pre-defined influenza-like illness and influenza-positive status by real-time RT-PCR were recruited at pediatric clinics for this observational study. Influenza viral load was measured for the most predominant subtype/lineage in each season. Using median dichotomized viral load as an outcome, a multilevel logistic regression model was applied to estimate the multivariable adjusted odds ratio (MOR) and 95% confidence interval (CI) for higher viral load. A total of 1,185 influenza-positive children were analyzed. The median log10 viral load copy number (copies per milliliter) was 5.5 (interquartile range, 4.6 to 6.1) and did not differ by vaccination status: 5.5 for unvaccinated, 5.7 for one dose, and 5.5 for two doses (p= 0.67). The MOR of vaccinated (one or two doses) versus unvaccinated children was 1.19 (95% CI: 0.86-1.64). Other factors showing significant associations with higher viral load were positive results for A(H1N1)pdm09 and A(H3N2) in comparison with B/Yamagata. The respective MORs were 3.25 (95% CI: 2.28-4.64) and 1.81 (95% CI: 1.32-2.49). Significantly elevated MORs against higher viral load were also observed for higher body temperature at influenza diagnosis and shorter duration from fever onset to specimen collection. No association was observed between inactivated-influenza vaccination and viral load at influenza-positive diagnosis. Influenza subtype/lineage, body temperature, and time elapsed since fever onset were significantly associated with viral load.

Differential Induction of Interferon-Stimulated Genes by Cell-Based Versus Egg-Based Quadrivalent Influenza Vaccines in Children During the 2018-2019 Season.

Cell-based quadrivalent-inactivated influenza vaccine has been shown to have higher vaccine effectiveness than traditional egg-based quadrivalent-inactivated influenza vaccine. This is observed despite similar levels of serum hemagglutinin antibodies induced by each vaccine. In this study, we examine peripheral immune activation after egg-based or cell-based influenza vaccination in a clinical trial in children. Peripheral blood mononuclear cells were isolated, and ribonucleic acid was sequenced from 81 study participants (41 Fluzone, egg based and 40 Flucelvax, cell based) pre- and 7 days postvaccination. Seroconversion was assessed by hemagglutinin inhibition assay. Differential gene expression was determined and pathway analysis was conducted. Cell-based influenza vaccine induced greater interferon-stimulated and innate immune gene activation compared with egg-based influenza vaccine. Participants who seroconverted had increased interferon-signaling activation versus those who did not seroconvert. These data suggest that cell-based influenza vaccine stimulates immune activation differently from egg-based influenza vaccine, shedding light on reported differences in vaccine effectiveness.

Caregivers' understanding of childhood influenza vaccination during the epidemic in China. A mixed-methods study.

Influenza vaccination uptake among young children has been poor in China, but it is unclear how it changed during the COVID-19. This study aimed to investigate the uptake status and reasons of childhood influenza vaccination during the pandemic in China. A mixed-methods study combining a questionnaire survey and semi-structured interviews was conducted in Anhui, Shaanxi, and Guangdong provinces between September and November 2021. 2081 caregivers completed the valid questionnaire. 38 caregivers participated in interviews, and data were analyzed thematically, using deductive and inductive coding. A total of 2081 caregivers completed the valid questionnaire, and 38 caregivers participated in interviews. Among the caregivers, a total of 1796 were in the age group for high-risk groups in the 2019-2020 flu season, and 46.10% reported that their children received influenza vaccination in the 2019-2020 flu season; 43.63% said that they vaccinated their children against influenza in the 2020-2021 flu season. Many caregivers indicated that the adoption of nonpharmacologic interventions (NPIs) during COVID-19 reduced the risk of influenza infection for children. Most caregivers consider the severity of influenza to be low, and some confused the common cold with influenza. Meanwhile, some caregivers lack confidence in the vaccine's effectiveness and importance. They thought that vaccines are not effective in preventing the constantly mutating virus. Despite clear perceptions about the severity of influenza and the effectiveness of the vaccine, we found that most caregivers did not receive any relevant medical information, and the communication about vaccines between caregivers and professional information sources, such as healthcare workers, is inadequate. Hence, caregivers have no scientific evidence to back up their perceptions. In terms of access to vaccination service, caregivers reported conflicts between time of vaccination service and their schedule, and the need for vaccine prices to be reduced. Targeted interventions are needed to address caregivers' lack of risk perception on influenza during COVID-19 and promote communication between caregivers and professional information sources. Extending vaccination service hours and increasing the number of vaccine clinics close to residential areas and expansion of financing sources for self-paid vaccination could facilitate the access to influenza vaccination service.

Memory-like innate response to booster vaccination with MF-59 adjuvanted influenza vaccine in children

The pediatric population receives the majority of vaccines globally, yet there is a paucity of studies on the transcriptional response induced by immunization in this special population. In this study, we performed a systems-level analysis of immune responses to the trivalent inactivated influenza vaccine adjuvanted with MF-59 in children (15–24 months old) and in young, healthy adults. We analyzed transcriptional responses elicited by vaccination in peripheral blood, as well as cellular and antibody responses following primary and booster vaccinations. Our analysis revealed that primary vaccination induced a persistent transcriptional signature of innate immunity; booster vaccination induced a transcriptional signature of an enhanced memory-like innate response, which was consistent with enhanced activation of myeloid cells assessed by flow cytometry. Furthermore, we identified a transcriptional signature of type 1 interferon response post-booster vaccination and at baseline that was correlated with the local reactogenicity to vaccination and defined an early signature that correlated with the hemagglutinin antibody titers. These results highlight an adaptive behavior of the innate immune system in evoking a memory-like response to secondary vaccination and define molecular correlates of reactogenicity and immunogenicity in infants.