Indirect protection from vaccinating children against influenza in households.
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ABSTRACT:
SUBMITTER: Tsang TK
PROVIDER: S-EPMC6328591 | biostudies-literature | 2019 Jan
REPOSITORIES: biostudies-literature
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Project description:Influenza vaccination is an important intervention to prevent influenza virus infection. Our previous analysis suggested that indirect protection is limited in an influenza B epidemic in Hong Kong. We further analyzed six influenza A epidemics to determine such potential. We applied a statistical model to estimate household transmission dynamics in the 3 influenza A(H3N2) and 3 pandemic influenza A(H1N1) epidemics. Then, we estimated the reduction in infection risk among unvaccinated household members when all children in households are vaccinated, with different assumptions on vaccine efficacy (VE). In the optimal scenario that VE was 70%, the reduction to the total probability of infection was only marginal, with relative probabilities ranged from 0.91-0.94 when all children in households were vaccinated because community was by far the main source of infection during the six epidemics in our study. The proportion of cases attributed to household transmission was 10% (95% CrI: 7%, 13%). Individual influenza vaccination is important even when other household members are vaccinated, given the degree of indirect protection is small.
| S-EPMC9610389 | biostudies-literature
Project description:Influenza virus infection is responsible for significant morbidity and mortality in the pediatric and pregnant women populations, with deaths frequently caused by severe influenza-associated lower respiratory tract infection and acute respiratory distress syndrome (ARDS). An appropriate immune response requires controlling the viral infection through activation of antiviral defenses, which involves cells of the lung and immune system. High levels of viral infection or high levels of inflammation in the lower airways can contribute to ARDS. Pregnant women and young children, especially those born prematurely, may develop serious complications if infected with influenza virus. Vaccination against influenza will lead to lower infection rates and fewer complications, even if the vaccine is poorly matched to circulating viral strains, with maternal vaccination offering infants protection via antibody transmission through the placenta and breast milk. Despite the health benefits of the influenza vaccine, vaccination rates around the world remain well below targets. Trust in the use of vaccines among the public must be restored in order to increase vaccination rates and decrease the public health burden of influenza.
| S-EPMC6963306 | biostudies-literature
Project description:BACKGROUND:The present study aims to assess the cost-effectiveness of an influenza vaccination program for children in the Netherlands. This requires an evaluation of the long-term impact of such a program on the burden of influenza across all age groups, using a transmission model that accounts for the seasonal variability in vaccine effectiveness and the shorter duration of protection following vaccination as compared to natural infection. METHODS:We performed a cost-effectiveness analysis based on a stochastic dynamic transmission model that has been calibrated to reported GP visits with influenza-like illness in the Netherlands over 11 seasons (2003/2004 to 2014/2015). We analyzed the costs and effects of extending the current program with vaccination of children aged 2-16 years at 50% coverage over 20 consecutive seasons. We measured the effects in quality-adjusted life-years (QALYs) and we adopted a societal perspective. RESULTS:The childhood vaccination program is estimated to have an average incremental cost-effectiveness ratio (ICER) of €3944 per QALY gained and is cost-effective in the general population (across 1000 simulations; conventional Dutch threshold of €20,000 per QALY gained). The childhood vaccination program is not estimated to be cost-effective for the target-group itself with an average ICER of €57,054 per QALY gained. Uncertainty analyses reveal that these ICERs hide a wide range of outcomes. Even though introduction of a childhood vaccination program decreases the number of infections, it tends to lead to larger epidemics: in 23.3% of 1000 simulations, the childhood vaccination program results in an increase in seasons with a symptomatic attack rate larger than 5%, which is expected to cause serious strain on the health care system. In 6.4% of 1000 simulations, the childhood vaccination program leads to a net loss of QALYs. These findings are robust across different targeted age groups and vaccination coverages. CONCLUSIONS:Modeling indicates that childhood influenza vaccination is cost-effective in the Netherlands. However, childhood influenza vaccination is not cost-effective when only outcomes for the children themselves are considered. In approximately a quarter of the simulations, the introduction of a childhood vaccination program increases the frequency of seasons with a symptomatic attack rate larger than 5%. The possibility of an overall health loss cannot be excluded.
| S-EPMC6958762 | biostudies-literature
Project description:BackgroundPrevious studies have established that antibody titer measured by the hemagglutination-inhibiting (HAI) assay is correlated with protection against influenza virus infection, with an HAI titer of 1:40 generally associated with 50% protection.MethodsWe recruited index cases with confirmed influenza virus infection from outpatient clinics, and followed up their household contacts for 7-10 days to identify secondary infections. Serum samples collected from a subset of household contacts were tested by HAI and microneutralization (MN) assays against prevalent influenza viruses. We analyzed the data using an individual hazard-based transmission model that adjusted for age and vaccination history.ResultsCompared to a reference group with antibody titers <1:10, we found that HAI titers of 1:40 against influenza A(H1N1) and A(H3N2) were associated with 31% (95% confidence interval [CI], 13%-46%) and 31% (CI, 1%-53%) protection against polymerase chain reaction (PCR)-confirmed A(H1N1) and A(H3N2) virus infection, respectively, while an MN titer of 1:40 against A(H3N2) was associated with 49% (95% CI, 7%-81%) protection against PCR-confirmed A(H3N2) virus infection.ConclusionsAn HAI titer of 1:40 was associated with substantially less than 50% protection against PCR-confirmed influenza virus infection within households, perhaps because of exposures of greater duration or intensity in that confined setting.
| S-EPMC4148604 | biostudies-literature
Project description:BackgroundIndirect herd effect from vaccination of children offers potential for improving the effectiveness of influenza prevention in the remaining unvaccinated population. Static models used in cost-effectiveness analyses cannot dynamically capture herd effects. The objective of this study was to develop a methodology to allow herd effect associated with vaccinating children against seasonal influenza to be incorporated into static models evaluating the cost-effectiveness of influenza vaccination.MethodsTwo previously published linear equations for approximation of herd effects in general were compared with the results of a structured literature review undertaken using PubMed searches to identify data on herd effects specific to influenza vaccination. A linear function was fitted to point estimates from the literature using the sum of squared residuals.ResultsThe literature review identified 21 publications on 20 studies for inclusion. Six studies provided data on a mathematical relationship between effective vaccine coverage in subgroups and reduction of influenza infection in a larger unvaccinated population. These supported a linear relationship when effective vaccine coverage in a subgroup population was between 20% and 80%. Three studies evaluating herd effect at a community level, specifically induced by vaccinating children, provided point estimates for fitting linear equations. The fitted linear equation for herd protection in the target population for vaccination (children) was slightly less conservative than a previously published equation for herd effects in general. The fitted linear equation for herd protection in the non-target population was considerably less conservative than the previously published equation.ConclusionsThis method of approximating herd effect requires simple adjustments to the annual baseline risk of influenza in static models: (1) for the age group targeted by the childhood vaccination strategy (i.e. children); and (2) for other age groups not targeted (e.g. adults and/or elderly). Two approximations provide a linear relationship between effective coverage and reduction in the risk of infection. The first is a conservative approximation, recommended as a base-case for cost-effectiveness evaluations. The second, fitted to data extracted from a structured literature review, provides a less conservative estimate of herd effect, recommended for sensitivity analyses.
| S-EPMC3570298 | biostudies-literature
Project description:BackgroundBoth the health care workers (HCWs) and children are target groups for pandemic influenza vaccination. The coverage of the target populations is an important determinant for impact of mass vaccination. The objective of this study is to determine the attitudes of HCWs as parents, toward vaccinating their children with pandemic influenza A/H1N1 vaccine.MethodsA cross-sectional questionnaire survey was conducted with health care workers (HCWs) in a public hospital during December 2009 in Istanbul. All persons employed in the hospital with or without a health-care occupation are accepted as HCW. The HCWs who are parents of children 6 months to 18 years of age were included in the study. Pearson's chi-square test and logistic regression analysis was applied for the statistical analyses.ResultsA total of 389 HCWs who were parents of children aged 6 months-18 years participated study. Among all participants 27.0% (n = 105) reported that themselves had been vaccinated against pandemic influenza A/H1N1. Two third (66.1%) of the parents answered that they will not vaccinate their children, 21.1% already vaccinated and 12.9% were still undecided. Concern about side effect was most reported reason among who had been not vaccinated their children and among undecided parents. The second reason for refusing the pandemic vaccine was concerns efficacy of the vaccine. Media was the only source of information about pandemic influenza in nearly one third of HCWs. Agreement with vaccine safety, self receipt of pandemic influenza A/H1N1 vaccine, and trust in Ministry of Health were found to be associated with the positive attitude toward vaccinating their children against pandemic influenza A/H1N1.ConclusionsPersuading parents to accept a new vaccine seems not be easy even if they are HCWs. In order to overcome the barriers among HCWs related to pandemic vaccines, determination of their misinformation, attitudes and behaviors regarding the pandemic influenza vaccination is necessary. Efforts for orienting the HCWs to use evidence based scientific sources, rather than the media for information should be considered by the authorities.
| S-EPMC3091558 | biostudies-literature
Project description:COVID-19 vaccines have been introduced in children and adolescents in many countries. However, high levels of community transmission and infection-derived immunity make the decision to introduce COVID-19 vaccination of children in countries yet to do so particularly challenging. For example, other vaccine preventable diseases, including measles and polio, generally have far higher childhood morbidity and mortality in low-income and middle-income countries (LMICs) than COVID-19, and coverage with these vaccines has declined during the pandemic. Many countries are yet to introduce pneumococcal conjugate and rotavirus vaccines for children, which prevent common causes of childhood death, or human papillomavirus vaccine for adolescents. The Pfizer and Moderna COVID-19 vaccines that have been widely tested in children and adolescents have a positive risk-benefit profile. However, the benefit is less compared with other life-saving vaccines in this age group, particularly in LMICs and settings with widespread infection-derived immunity. The resources required for rollout may also pose a considerable challenge in LMICs. In this paper, we describe COVID-19 in children, with a focus on LMICs, and summarise the published literature on safety, efficacy and effectiveness of COVID-19 vaccination in children and adolescents. We highlight the complexity of decision-making regarding COVID-19 vaccination of children now that most of this low-risk population benefit from infection-derived immunity. We emphasise that at-risk groups should be prioritised for COVID-19 vaccination; and that if COVID-19 vaccines are introduced for children, the opportunity should be taken to improve coverage of routine childhood vaccines and preventative healthcare. Additionally, we highlight the paucity of epidemiological data in LMICs, and that for future epidemics, measures need to be taken to ensure equitable access to safe and efficacious vaccines before exposure to infection.
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Project description:This article examines issues related to COVID-19 inoculations for children. The bulk of the official COVID-19-attributed deaths per capita occur in the elderly with high comorbidities, and the COVID-19 attributed deaths per capita are negligible in children. The bulk of the normalized post-inoculation deaths also occur in the elderly with high comorbidities, while the normalized post-inoculation deaths are small, but not negligible, in children. Clinical trials for these inoculations were very short-term (a few months), had samples not representative of the total population, and for adolescents/children, had poor predictive power because of their small size. Further, the clinical trials did not address changes in biomarkers that could serve as early warning indicators of elevated predisposition to serious diseases. Most importantly, the clinical trials did not address long-term effects that, if serious, would be borne by children/adolescents for potentially decades. A novel best-case scenario cost-benefit analysis showed very conservatively that there are five times the number of deaths attributable to each inoculation vs those attributable to COVID-19 in the most vulnerable 65+ demographic. The risk of death from COVID-19 decreases drastically as age decreases, and the longer-term effects of the inoculations on lower age groups will increase their risk-benefit ratio, perhaps substantially.
| S-EPMC8437699 | biostudies-literature
Project description:With the recent licensure of mRNA vaccines against COVID-19 in the 5- to 11-year-old age group, the public health impact of a childhood immunization campaign is of interest. Using a mathematical epidemiological model, we project that childhood vaccination carries minimal risk and yields modest public health benefits. These include large relative reductions in child morbidity and mortality, although the absolute reduction is small because these events are rare. Furthermore, the model predicts "altruistic" absolute reductions in adult cases, hospitalizations, and mortality. However, vaccinating children to benefit adults should be considered from an ethical as well as a public health perspective. From a global health perspective, an additional ethical consideration is the justice of giving priority to children in high-income settings at low risk of severe disease while vaccines have not been made available to vulnerable adults in low-income settings. IMPORTANCE Countries have recently begun implementation of childhood vaccination against SARS-CoV-2 with the Pfizer/BioNTech mRNA vaccine in children 5 to 11 years of age. Because SARS-CoV-2 disease severity is remarkably age dependent, vaccinating children may have modest public health benefits, relative to the unequivocal benefit of vaccinating vulnerable older adults. Furthermore, vaccinating children to "altruistically" increase herd immunity should be considered from an ethical as well as a public health perspective. An additional question is related to global social justice: should priority be given to vaccinating children in high-income settings while older adult populations in low-resource settings have limited access to vaccine? To address the risks and benefits of childhood vaccination, we provide a balanced commentary, supported by a mathematical epidemiological model, using Australia and Alberta, Canada, as case studies. We give highlights of the modeling findings in the commentary and include details in the supplemental materials for interested readers.
| S-EPMC8764932 | biostudies-literature
Project description:The historical Japanese influenza vaccination program targeted at schoolchildren provides a unique opportunity to evaluate the indirect benefits of vaccinating high-transmitter groups to mitigate disease burden among seniors. Here we characterize the indirect mortality benefits of vaccinating schoolchildren based on data from Japan and the US.We compared age-specific influenza-related excess mortality rates in Japanese seniors aged ?65 years during the schoolchildren vaccination program (1978-1994) and after the program was discontinued (1995-2006). Indirect vaccine benefits were adjusted for demographic changes, socioeconomics and dominant influenza subtype; US mortality data were used as a control.We estimate that the schoolchildren vaccination program conferred a 36% adjusted mortality reduction among Japanese seniors (95%CI: 17-51%), corresponding to ?1,000 senior deaths averted by vaccination annually (95%CI: 400-1,800). In contrast, influenza-related mortality did not change among US seniors, despite increasing vaccine coverage in this population.The Japanese schoolchildren vaccination program was associated with substantial indirect mortality benefits in seniors.
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