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Influenza vaccine effectiveness (VE) wanes over the course of a temperate climate winter season but little data are available from tropical countries with year-round influenza virus activity. In Singapore, a retrospective cohort study of adults vaccinated from 2013 to 2017 was conducted. Influenza vaccine failure was defined as hospital admission with polymerase chain reaction-confirmed influenza infection 2-49 weeks after vaccination. Relative VE was calculated by splitting the follow-up period into 8-week episodes (Lexis expansion) and the odds of influenza infection in the first 8-week period after vaccination (weeks 2-9) compared with subsequent 8-week periods using multivariable logistic regression adjusting for patient factors and influenza virus activity. Records of 19 298 influenza vaccinations were analysed with 617 (3.2%) influenza infections. Relative VE was stable for the first 26 weeks post-vaccination, but then declined for all three influenza types/subtypes to 69% at weeks 42-49 (95% confidence interval (CI) 52-92%, P = 0.011). VE declined fastest in older adults, in individuals with chronic pulmonary disease and in those who had been previously vaccinated within the last 2 years. Vaccine failure was significantly associated with a change in recommended vaccine strains between vaccination and observation period (adjusted odds ratio 1.26, 95% CI 1.06-1.50, P = 0.010).
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Vacinas contra Influenza/imunologia , Influenza Humana/prevenção & controle , Humanos , Vigilância da População , Estudos Retrospectivos , Fatores de Tempo , Clima Tropical , VacinaçãoRESUMO
BACKGROUND: A yellow fever epidemic occurred in Angola in 2016 with 884 laboratory confirmed cases and 373 deaths. Eleven unvaccinated Chinese nationals working in Angola were also infected and imported the disease to China, thereby presenting the first importation of yellow fever into Asia. In Angola, there are about 259,000 Chinese foreign workers. The fact that 11 unvaccinated Chinese workers acquired yellow fever suggests that many more Chinese workers in Angola were not vaccinated. METHODS: We applied a previously developed model to back-calculate the number of unvaccinated Chinese workers in Angola in order to determine the extent of lack of vaccine coverage. RESULTS: Our models suggest that none of the 259,000 Chinese had been vaccinated, although yellow fever vaccination is mandated by the International Health Regulations. CONCLUSION: Governments around the world including China need to ensure that their citizens obtain YF vaccination when traveling to countries where such vaccines are required in order to prevent the international spread of yellow fever.
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Vacina contra Febre Amarela/uso terapêutico , Febre Amarela/epidemiologia , Angola/epidemiologia , Povo Asiático , China/epidemiologia , Surtos de Doenças/prevenção & controle , Epidemias , Humanos , Migrantes/estatística & dados numéricos , Viagem , Vacinação , Febre Amarela/prevenção & controleRESUMO
BACKGROUND: Assessments of vaccine efficacy and safety capture only the minimum information needed for regulatory approval, rather than the full public health value of vaccines. Vaccine efficacy provides a measure of proportionate disease reduction, is usually limited to etiologically confirmed disease, and focuses on the direct protection of the vaccinated individual. Herein, we propose a broader scope of methods, measures and outcomes to evaluate the effectiveness and public health impact to be considered for evidence-informed policymaking in both pre- and post-licensure stages. DISCUSSION: Pre-licensure: Regulatory concerns dictate an individually randomised clinical trial. However, some circumstances (such as the West African Ebola epidemic) may require novel designs that could be considered valid for licensure by regulatory agencies. In addition, protocol-defined analytic plans for these studies should include clinical as well as etiologically confirmed endpoints (e.g. all cause hospitalisations, pneumonias, acute gastroenteritis and others as appropriate to the vaccine target), and should include vaccine-preventable disease incidence and 'number needed to vaccinate' as outcomes. Post-licensure: There is a central role for phase IV cluster randomised clinical trials that allows for estimation of population-level vaccine impact, including indirect, total and overall effects. Dynamic models should be prioritised over static models as the constant force of infection assumed in static models will usually underestimate the effectiveness and cost-effectiveness of the immunisation programme by underestimating indirect effects. The economic impact of vaccinations should incorporate health and non-health benefits of vaccination in both the vaccinated and unvaccinated populations, thus allowing for estimation of the net social value of vaccination. CONCLUSIONS: The full benefits of vaccination reach beyond direct prevention of etiologically confirmed disease and often extend across the life course of a vaccinated person, prevent outcomes in the wider community, stabilise health systems, promote health equity, and benefit local and national economies. The degree to which vaccinations provide broad public health benefits is stronger than for other preventive and curative interventions.
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Avaliação de Processos e Resultados em Cuidados de Saúde , Saúde Pública , Vacinas , Análise Custo-Benefício , Hospitalização , Humanos , Programas de ImunizaçãoRESUMO
The timing and origin of Zika virus (ZIKV) introduction in Brazil has been the subject of controversy. Initially, it was assumed that the virus was introduced during the FIFA World Cup in June-July 2014. Then, it was speculated that ZIKV may have been introduced by athletes from French Polynesia (FP) who competed in a canoe race in Rio de Janeiro in August 2014. We attempted to apply mathematical models to determine the most likely time window of ZIKV introduction in Brazil. Given that the timing and origin of ZIKV introduction in Brazil may be a politically sensitive issue, its determination (or the provision of a plausible hypothesis) may help to prevent undeserved blame. We used a simple mathematical model to estimate the force of infection and the corresponding individual probability of being infected with ZIKV in FP. Taking into account the air travel volume from FP to Brazil between October 2013 and March 2014, we estimated the expected number of infected travellers arriving at Brazilian airports during that period. During the period between December 2013 and February 2014, 51 individuals travelled from FP airports to 11 Brazilian cities. Basing on the calculated force of ZIKV infection (the per capita rate of new infections per time unit) and risk of infection (probability of at least one new infection), we estimated that 18 (95% CI 12-22) individuals who arrived in seven of the evaluated cities were infected. When basic ZIKV reproduction numbers greater than one were assumed in the seven evaluated cities, ZIKV could have been introduced in any one of the cities. Based on the force of infection in FP, basic reproduction ZIKV number in selected Brazilian cities, and estimated travel volume, we concluded that ZIKV was most likely introduced and established in Brazil by infected travellers arriving from FP in the period between October 2013 and March 2014, which was prior to the two aforementioned sporting events.
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Surtos de Doenças , Viagem , Infecção por Zika virus/epidemiologia , Zika virus/fisiologia , Número Básico de Reprodução , Brasil/epidemiologia , Humanos , Modelos Teóricos , Polinésia/epidemiologia , Risco , Infecção por Zika virus/virologiaRESUMO
The classical Ross-Macdonald model is often utilized to model vector-borne infections; however, this model fails on several fronts. First, using measured (or estimated) parameters, which values are accepted from the literature, the model predicts a much greater number of cases than what is usually observed. Second, the model predicts a single large outbreak that is followed by decades of much smaller outbreaks, which is not consistent with what is observed. Usually towns or cities report a number of recurrences for many years, even when environmental changes cannot explain the disappearance of the infection between the peaks. In this paper, we continue to examine the pitfalls in modelling this class of infections, and explain that, if properly used, the Ross-Macdonald model works and can be used to understand the patterns of epidemics and even, to some extent, be used to make predictions. We model several outbreaks of dengue fever and show that the variable pattern of yearly recurrence (or its absence) can be understood and explained by a simple Ross-Macdonald model modified to take into account human movement across a range of neighbourhoods within a city. In addition, we analyse the effect of seasonal variations in the parameters that determine the number, longevity and biting behaviour of mosquitoes. Based on the size of the first outbreak, we show that it is possible to estimate the proportion of the remaining susceptible individuals and to predict the likelihood and magnitude of the eventual subsequent outbreaks. This approach is described based on actual dengue outbreaks with different recurrence patterns from some Brazilian regions.
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Insecticide-treated clothing has been used for many years by the military and in recreational activities as personal protection against bites from a variety of arthropods including ticks, chigger mites, sandflies and mosquitoes. Permethrin is the most commonly used active ingredient, but others, including bifenthrin, deltamethrin, cyfluthrin, DEET (N,N-diethyl-3-methylbenz-amide) and KBR3023, have also been trialled. Treatment is usually carried out by home or factory dipping. However, new microencapsulation technologies which may prolong the activity of insecticides on clothing are now available and may help to overcome the inevitable reduction in efficacy over time that occurs as a result of washing, ultraviolet light exposure, and the normal wear and tear of the fabric. The aim of this article is to review the evidence base for the use of insecticide-treated clothing for protection against bites from arthropods and its effect on arthropod-borne pathogen transmission. Although some studies do demonstrate protection against pathogen transmission, there are surprisingly few, and the level of protection provided varies according to the disease and the type of study conducted. For example, insecticide-treated clothing has been reported to give between 0% and 75% protection against malaria and between 0% and 79% protection against leishmaniasis. Studies vary in the type of treatment used, the age group of participants, the geographical location of the study, and the pathogen transmission potential. This makes it difficult to compare and assess intervention trials. Overall, there is substantial evidence that insecticide-treated clothing can provide protection against arthropod bites. Bite protection evidence suggests that insecticide-treated clothing may be useful in the prevention of pathogen transmission, but further investigations are required to accurately demonstrate transmission reduction.
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Vetores Artrópodes/efeitos dos fármacos , Vestuário , Controle de Doenças Transmissíveis/métodos , Mordeduras e Picadas de Insetos/prevenção & controle , Inseticidas/farmacologia , Permetrina/farmacologia , AnimaisRESUMO
In 2012, Madeira reported its first major outbreak of dengue. To identify the origin of the imported dengue virus, we investigated the interconnectivity via air travel between dengue-endemic countries and Madeira, and compared available sequences against GenBank. There were 22,948 air travellers to Madeira in 2012, originating from twenty-nine dengue-endemic countries; 89.6% of these international travellers originated from Venezuela and Brazil. We developed an importation index that takes into account both travel volume and the extent of dengue incidence in the country of origin. Venezuela and Brazil had by far the highest importation indices compared with all other dengue-endemic countries. The importation index for Venezuela was twice as high as that for Brazil. When taking into account seasonality in the months preceding the onset of the Madeira outbreak, this index was even seven times higher for Venezuela than for Brazil during this time. Dengue sequencing shows that the virus responsible for the Madeira outbreak was most closely related to viruses circulating in Venezuela, Brazil and Columbia. Applying the importation index, Venezuela was identified as the most likely origin of importation of dengue virus via travellers to Madeira. We propose that the importation index is a new additional tool that can help to identify and anticipate the most probable country of origin for importation of dengue into currently non-endemic countries.
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Vírus da Dengue/isolamento & purificação , Dengue/epidemiologia , Surtos de Doenças/estatística & dados numéricos , RNA Viral/genética , Viagem , Dengue/diagnóstico , Dengue/transmissão , Dengue/virologia , Vírus da Dengue/genética , Genótipo , Humanos , Epidemiologia Molecular , Portugal/epidemiologia , Análise de Sequência de DNARESUMO
Dengue is the most frequent arboviral disease and is expanding geographically. Dengue is also increasingly being reported in travellers, in particular in travellers to Thailand. However, data to quantify the risk of travellers acquiring dengue when travelling to Thailand are lacking. Using mathematical modelling, we set out to estimate the risk of non-immune persons acquiring dengue when travelling to Thailand. The model is deterministic with stochastic parameters and assumes a Poisson distribution for the mosquitoes' biting rate and a Gamma distribution for the probability of acquiring dengue from an infected mosquito. From the force of infection we calculated the risk of dengue acquisition for travellers to Thailand arriving in a typical year (averaged over a 17-year period) in the high season of transmission. A traveller arriving in the high season of transmission and remaining for 7 days has a risk of acquiring dengue of 0·2% (95% CI 0·16-0·23), whereas the risk for travel of 15 and 30 days' duration is 0·46% (95% CI 0·41-0·50) and 0·81% (95% CI 0·76-0·87), respectively. Our data highlight that the risk of non-immune travellers acquiring dengue in Thailand is substantial. The incidence of 0·81% after a 1-month stay is similar to that reported in prospective seroconversion studies in Israeli travellers to Thailand, highlighting that our models are consistent with actual data. Risk estimates based on mathematical modelling offer more detailed information depending on various travel scenarios, and will help the travel medicine provider give better evidence-based advice for travellers to dengue-endemic countries.
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Culicidae , Vírus da Dengue/patogenicidade , Dengue/epidemiologia , Medição de Risco/métodos , Viagem , Animais , Dengue/imunologia , Dengue/transmissão , Humanos , Incidência , Modelos Teóricos , Estudos Prospectivos , Estações do Ano , Processos Estocásticos , Tailândia/epidemiologiaRESUMO
Our objective was to determine the association between temperature, humidity, rainfall and dengue activity in Singapore, after taking into account lag periods as well as long-term climate variability such as the El Niño Southern Oscillation Index (SOI). We used a Poisson model which allowed for autocorrelation and overdispersion in the data. We found weekly mean temperature and mean relative humidity as well as SOI to be significantly and independently associated with dengue notifications. There was an interaction effect by periods of dengue outbreaks, but periods where El Niño was present did not moderate the relationship between humidity and temperature with dengue notifications. Our results help to understand the temporal trends of dengue in Singapore, and further reinforce the findings that meteorological factors are important in the epidemiology of dengue.
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Dengue/epidemiologia , El Niño Oscilação Sul , Tempo (Meteorologia) , Humanos , Modelos Estatísticos , Singapura/epidemiologiaAssuntos
Cloroquina/administração & dosagem , Resistência à Insulina , Lipoproteínas/metabolismo , Adulto , Glicemia/efeitos dos fármacos , Glicemia/metabolismo , Colesterol/sangue , Relação Dose-Resposta a Droga , Esquema de Medicação , Feminino , Humanos , Lipoproteínas/sangue , Masculino , Síndrome Metabólica/tratamento farmacológico , Síndrome Metabólica/metabolismo , Triglicerídeos/sangueRESUMO
PURPOSE OF REVIEW: The COVID-19 pandemic poses a major global health threat. The rapid spread was facilitated by air travel although rigorous travel bans and lockdowns were able to slow down the spread. How does COVID-19 compare with other emerging viral diseases of the past two decades? RECENT FINDINGS: Viral outbreaks differ in many ways, such as the individuals most at risk e.g. pregnant women for Zika and the elderly for COVID-19, their vectors of transmission, their fatality rate, and their transmissibility often measured as basic reproduction number. The risk of geographic spread via air travel differs significantly between emerging infectious diseases. COVID-19 is not associated with the highest case fatality rate compared with other emerging viral diseases such as SARS and Ebola, but the combination of a high reproduction number, superspreading events and a globally immunologically naïve population has led to the highest global number of deaths in the past 20 decade compared to any other pandemic.
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PURPOSE OF REVIEW: Japanese encephalitis is the most common vaccine-preventable viral encephalitis in Asia. In view of the production cessation of the inactivated mouse brain-derived Japanese encephalitis vaccine, it is timely to provide an update on new Japanese encephalitis vaccines and revised vaccine recommendations. RECENT FINDINGS: A new inactivated, adjuvanted, Vero cell-culture-based Japanese encephalitis vaccine, IC51, was licensed in Europe and the United States in 2009. Administered in a two-dose regimen at 0 and 28 days, it was shown to be well tolerated and produce high seroconversion rates. In addition, Chimerivax Japanese encephalitis, a novel live-attenuated one-dose chimeric vaccine comprising the structural genes of SA 14-14-2 virus and nonstructural genes of yellow fever 17D virus, is in the process of getting licensed in Australia and in south east Asia. SUMMARY: Previous recommendations for Japanese encephalitis vaccination of travelers were predicated on minimizing exposure to a mouse-brain-derived vaccine with a poorly understood and worrisome safety profile, whereas the risk of acquiring Japanese encephalitis itself during travel was assessed to be relatively low. With the availability of a new cell-culture-derived vaccine IC51 with an excellent safety profile, it is appropriate to reconsider benefit-risk considerations for the vaccination of travelers. These considerations are reflected in the March 2010 revised recommendations by the United States Advisory Committee on Immunization Practices.
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Encefalite Japonesa/prevenção & controle , Vacinas contra Encefalite Japonesa/imunologia , Vacinação/métodos , Ásia , Austrália , Europa (Continente) , Imunização Secundária/métodos , Vacinas contra Encefalite Japonesa/efeitos adversos , Viagem , Estados Unidos , Vacinas Atenuadas/efeitos adversos , Vacinas Atenuadas/imunologia , Vacinas de Produtos Inativados/efeitos adversos , Vacinas de Produtos Inativados/imunologiaRESUMO
W135 meningococcal disease was imported into Singapore in 2000 via Hajj pilgrims. Previous studies have showed sustained carriage of W135 with the potential for further transmission within communities. We therefore set out to determine whether W135 meningococcal disease would become endemic in Singapore after its introduction in 2000. Cases occurred until 2003, but no further cases have been reported since 2004.
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Infecções Meningocócicas/epidemiologia , Neisseria meningitidis Sorogrupo W-135 , Surtos de Doenças , Humanos , Infecções Meningocócicas/transmissão , Singapura/epidemiologiaRESUMO
Dengue activity depends on fluctuations in Aedes populations which in turn are known to be influenced by climate factors including temperature, humidity and rainfall. It has been hypothesized that haze may reduce dengue transmission. Due to its geographical location Singapore suffers almost every year from hazes caused by wildfires from Indonesia. Such hazes have a significant impact on pollution indexes in Singapore. We set out to study the relationship of dengue activity and haze (measured as pollution standard index) in Singapore, using ARIMA models. We ran different univariate models, each encompassing a different lag period for the effects of haze and temperature (from lag 0 to lag 12 weeks). We analysed the data on a natural logarithmic scale to stabilize the variance and improve the estimation. No association between dengue activity and haze was found. Our findings do not lend support to the hypothesis that haze is associated with reduced dengue activity in Singapore.
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Poluentes Atmosféricos/análise , Culicidae/crescimento & desenvolvimento , Dengue/epidemiologia , Material Particulado/análise , Poluição do Ar/estatística & dados numéricos , Animais , Culicidae/patogenicidade , Dengue/transmissão , Humanos , Modelos Teóricos , Dinâmica Populacional , Singapura/epidemiologia , TemperaturaRESUMO
BACKGROUND: Cruise ships carry a large number of people in confined spaces with relative homogeneous mixing. On 3 February, 2020, an outbreak of COVID-19 on cruise ship Diamond Princess was reported with 10 initial cases, following an index case on board around 21-25th January. By 4th February, public health measures such as removal and isolation of ill passengers and quarantine of non-ill passengers were implemented. By 20th February, 619 of 3700 passengers and crew (17%) were tested positive. METHODS: We estimated the basic reproduction number from the initial period of the outbreak using SEIR models. We calibrated the models with transient functions of countermeasures to incidence data. We additionally estimated a counterfactual scenario in absence of countermeasures, and established a model stratified by crew and guests to study the impact of differential contact rates among the groups. We also compared scenarios of an earlier versus later evacuation of the ship. RESULTS: The basic reproduction rate was initially 4 times higher on-board compared to the ${R}_0$ in the epicentre in Wuhan, but the countermeasures lowered it substantially. Based on the modeled initial ${R}_0$ of 14.8, we estimated that without any interventions within the time period of 21 January to 19 February, 2920 out of the 3700 (79%) would have been infected. Isolation and quarantine therefore prevented 2307 cases, and lowered the ${R}_0$ to 1.78. We showed that an early evacuation of all passengers on 3 February would have been associated with 76 infected persons in their incubation time. CONCLUSIONS: The cruise ship conditions clearly amplified an already highly transmissible disease. The public health measures prevented more than 2000 additional cases compared to no interventions. However, evacuating all passengers and crew early on in the outbreak would have prevented many more passengers and crew from infection.
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Controle de Doenças Transmissíveis/métodos , Infecções por Coronavirus/epidemiologia , Infecções por Coronavirus/prevenção & controle , Modelos Estatísticos , Pandemias/prevenção & controle , Pneumonia Viral/epidemiologia , Pneumonia Viral/prevenção & controle , Navios , Número Básico de Reprodução , Betacoronavirus , COVID-19 , Humanos , Incidência , Quarentena , SARS-CoV-2RESUMO
The COVID-19 pandemic can no longer be mitigated by a nationwide approach of individual nations alone. Given its scale and accelerating expansion, COVID-19 requires a coordinated and simultaneous Whole- of-World approach that galvanizes clear global leadership and solidarity from all governments of the world. Considering an 'all hands-on deck' concept, we present a comprehensive list of tools and entities responsible for enabling them, as well a conceptual framework to achieve the maximum impact. The list is drawn from pandemic mitigation tools developed in response to past outbreaks including influenza, coronaviruses, and Ebola, and includes tools to minimize transmission in various settings including person-to-person, crowd, funerals, travel, workplace, and events and gatherings including business, social and religious venues. Included are the roles of individuals, communities, government and other sectors such as school systems, health, institutions, and business. While individuals and communities have significant responsibilities to prevent person-to-person transmission, other entities can play a significant role to enable individuals and communities to make use of the tools. Historic and current data indicate the role of political will, whole-of-government approach, and the role of early introduction of mitigation measures. There is also an urgent need to further elucidate the immunologic mechanisms underlying the epidemiological characteristics such as the low disease burden among women, and the role of COVID-19 in inducing Kawasaki-like syndromes in children. Understanding the role of and development of anti-inflammatory strategies based on our understanding of pro-inflammatory cytokines (IL1, IL-6) is also critical. Similarly, the role of oxygen therapy as an anti-inflammatory strategy is evident and access to oxygen therapy should be prioritized to avoid the aggravation of COVID-19 infection. We highlight the need for global solidarity to share both mitigation commodities and infrastructure between countries. Given the global reach of COVID-19 and potential for repeat waves of outbreaks, we call on all countries and communities to act synergistically and emphasize the need for synchronized pan-global mitigation efforts to minimize everyone's risk, to maximize collaboration, and to commit to shared progress.
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Betacoronavirus , Infecções por Coronavirus/epidemiologia , Pneumonia Viral/epidemiologia , COVID-19 , Surtos de Doenças , Feminino , Humanos , Masculino , Pandemias , SARS-CoV-2RESUMO
OBJECTIVES: Vaccination for dengue with the live attenuated tetravalent CYD-TDV vaccine (Dengvaxia®) is only recommended in individuals who have had prior dengue virus (DENV) infection. Rapid diagnostic tests (RDT) for past DENV infection would offer a convenient method for pre-vaccination screening at point-of-care. A systematic review was conducted to evaluate the performance of current dengue RDTs for determining dengue serostatus, using IgG antibodies against DENV as a marker of past infection. METHODS: PubMed and EMBASE databases were searched from 2000 to 2018 to identify studies evaluating dengue RDTs in individuals with known or possible previous DENV infection. Study quality was evaluated using GRADE and QUADAS-2 criteria. Semi-structured interviews were also performed with available dengue RDT manufacturers. RESULTS: The performance of four dengue IgG RDTs was determined in 3137 individuals across ten studies conducted in 13 countries, with serum used in most of the studies. No studies reported data for determining dengue serostatus, and limited data were available regarding cross-reactivity with other viruses. The majority of studies demonstrated sensitivities and specificities between 80% and 100% for dengue IgG detection in samples from secondary infection or convalescent time-points after recent infection. CONCLUSIONS: Although current dengue IgG RDTs have shown reasonable performance compared with laboratory-based tests in secondary infection, additional research is needed to determine how RDTs would perform in relevant populations targeted for vaccination. New RDTs or modifications to current RDTs are feasible and may optimize the performance of these tests for use in a pre-vaccination screening approach.
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Anticorpos Antivirais/sangue , Vírus da Dengue/imunologia , Dengue/diagnóstico , Dengue/imunologia , Imunoensaio/métodos , Testes Sorológicos/métodos , Adolescente , Adulto , Idoso , Idoso de 80 Anos ou mais , Criança , Pré-Escolar , Feminino , Humanos , Imunoglobulina G/sangue , Lactente , Recém-Nascido , Entrevistas como Assunto , Masculino , Pessoa de Meia-Idade , Sistemas Automatizados de Assistência Junto ao Leito , Sensibilidade e Especificidade , Fatores de Tempo , Adulto JovemRESUMO
The first licensed dengue vaccine, CYD-TDV (Dengvaxia) is efficacious in seropositive individuals, but increases the risk for severe dengue in seronegative persons about two years after administration of the first dose. For countries considering the introduction of Dengvaxia, WHO recommends a pre-vaccination screening strategy whereby only persons with evidence of a past dengue infection would be vaccinated. Policy-makers need to consider the risk-benefit of vaccination strategies based on such screening tests, the optimal age to introduce the vaccine, communication and implementation strategies. To address these questions, the Global Dengue and Aedes-transmitted diseases Consortium (GDAC) organized a 3-day workshop in January 2019 with country representatives from Asia and Latin America. The meeting discussions highlighted many challenges in introducing Dengvaxia, in terms of screening test characteristics, costs of such tests combined with a 3-dose schedule, logistics, achieving high coverage rates, vaccine confidence and communication; more challenges than for any other vaccine introduction programme. A screening test would require a high specificity to minimize individual risk, and at the same time high sensitivity to maximize individual and population benefit. The underlying seroprevalence dependent positive predictive value is the best indicator for an acceptable safety profile of a pre-vaccination screening strategy. The working groups discussed many possible implementation strategies. Addressing the bottlenecks in school-based vaccine introduction for Dengvaxia will also benefit other vaccines such as HPV and booster doses for tetanus and pertussis. Levels of public trust are highly variable and context specific, and understanding of population perceptions and concerns is essential to tailor interventions, monitor and mitigate risks.