Refusal of recommended travel-related vaccines among U.S. international travellers in Global TravEpiNet

Boostability after single-visit pre-exposure prophylaxis with rabies vaccine: a randomised controlled non-inferiority trial

BACKGROUND

After rabies pre-exposure prophylaxis (PrEP) vaccination, scarcely available rabies immunoglobulins are not required for post-exposure prophylaxis (PEP). However, PrEP is not sufficiently accessible as it is cost-intensive and time-intensive. This study investigates whether rabies PrEP schedules can be shortened to one visit, removing some of these barriers.

METHODS

In a block-randomised (2:2:2:1) controlled, multicentre non-inferiority trial, healthy adult travellers (aged 18-50 years and >50 years) were randomly assigned to (A) single-visit intramuscular (1·0 mL); (B) single-visit intradermal (0·2 mL); (C) standard two-visit intramuscular (1·0 mL; day 0 and 7) PrEP; or (D) no rabies vaccination. 6 months later, participants received simulated intramuscular rabies PEP (1·0 mL; day 0 and 3). Rabies virus neutralising antibody (RVNA) concentrations were measured repeatedly. The primary outcome was the fold increase in geometric mean RVNA concentrations between day 0 and 7 after simulated PEP for all participants. The two main comparisons of this primary outcome are between the standard two-visit schedule and the one-visit intramuscular schedule, and between the standard two-visit schedule and the one-visit intradermal schedule. The non-inferiority margin was 0·67. This study is registered with EudraCT, 2017-000089-31.

FINDINGS

Between May 16, 2018, and March 26, 2020, 288 healthy adult travellers were randomly assigned and 214 participants were evaluated for the primary outcome. Single-visit intramuscular rabies PrEP induced an anamnestic antibody response non-inferior compared with the two-visit intramuscular schedule; single-visit intradermal PrEP did not. The fold increases in the single-visit intramuscular and the single-visit intradermal schedule were 2·32 (95% CI [1·43-3·77]) and 1·11 (0·66-1·87) times as high as the fold increase in the standard schedule, respectively. No vaccine-related serious adverse events were observed. Adverse events related to vaccination were mostly mild.

INTERPRETATION

Single intramuscular rabies vaccination can effectively prime travellers (aged 18-50 years), and potentially other populations, and could replace current standard two-visit rabies vaccination as PrEP.

FUNDING

ZonMW.

TRANSLATION

For the Dutch translation of the abstract see Supplementary Materials section.

A decision support tool for risk-benefit analysis of Japanese encephalitis vaccine in travellers

BACKGROUND

During pre-travel consultations, clinicians and travellers face the challenge of weighing the risks verus benefits of Japanese encephalitis (JE) vaccination due to the high cost of the vaccine, low incidence in travellers (~1 in 1 million), but potentially severe consequences (~30% case-fatality rate). Personalised JE risk assessment based on the travellers' demographics and travel itinerary is challenging using standard risk matrices. We developed an interactive digital tool to estimate risks of JE infection and severe health outcomes under different scenarios to facilitate shared decision-making between clinicians and travellers.

METHODS

A Bayesian network (conditional probability) model risk-benefit analysis of JE vaccine in travellers was developed. The model considers travellers' characteristics (age, sex, co-morbidities), itinerary (destination, departure date, duration, setting of planned activities) and vaccination status to estimate the risks of JE infection, the development of symptomatic disease (meningitis, encephalitis), clinical outcomes (hospital admission, chronic neurological complications, death) and adverse events following immunization.

RESULTS

In low-risk travellers (e.g. to urban areas for <1 month), the risk of developing JE and dying is low (<1 per million) irrespective of the destination; thus, the potential impact of JE vaccination in reducing the risk of clinical outcomes is limited. In high-risk travellers (e.g. to rural areas in high JE incidence destinations for >2 months), the risk of developing symptomatic disease and mortality is estimated at 9.5 and 1.4 per million, respectively. JE vaccination in this group would significantly reduce the risk of symptomatic disease and mortality (by ~80%) to 1.9 and 0.3 per million, respectively.

CONCLUSION

The JE tool may assist decision-making by travellers and clinicians and could increase JE vaccine uptake. The tool will be updated as additional evidence becomes available. Future work needs to evaluate the usability of the tool. The interactive, scenario-based, personalised JE vaccine risk-benefit tool is freely available on www.VaxiCal.com.

Using the Health Belief Model to Predict Pre-Travel Health Decisions among U.S.-Based Travelers

International travelers are at increased risk of infectious disease, but almost half of Americans traveling to lower- and middle-income countries seek no health information before traveling. The Health Belief Model (HBM) can help evaluate decisions by categorizing behaviors into five categories: susceptibility, severity, benefits, barriers, and self-efficacy. This study sought to use the HBM to elucidate what may influence an individual to make certain pre-travel health decisions. We surveyed 604 participants who had recently traveled to an at-risk country. Participants were subset into nested groups: full population, sought any health information, and visited a clinic or health care provider (HCP). Survey questions were categorized according to the HBM, assembled into a priori models, and analyzed in each group using logistic regression with three main outcome variables: "Sought any pre-travel health information," "Visited clinic or HCP," and "Received vaccine." Of the 604 participants, 333 (55%) sought any health information, 245 (41% of total) reported visiting an HCP, and 166 (27% of total) reported receiving a vaccine before traveling. Models containing variables from the susceptibility and benefits categories were most successful in predicting all three outcomes; susceptibility was a more relevant consideration in information seeking and seeing a provider than vaccination, whereas benefits was relevant for all outcomes. Our results emphasize the importance of an individual's perceived susceptibility to disease and perceived benefit of interventions in predicting pre-travel health behaviors. Understanding this interaction can help shape how HCPs and public health entities can encourage health care seeking and vaccine uptake in travelers.

Profiles of travelers to intermediate-high health risk areas following the reopening of borders in the COVID-19 crisis: A clustering approach

BACKGROUND

The reactivation of international travel in 2021 has created a new scenario in which the profile of the traveler to medium-high health risk areas may well have changed. However, few studies have analyzed this new profile since the reopening of borders in that year.

METHODS

We designed an ad hoc questionnaire that was administered face-to-face by our medical team during appointments with 330 travelers in the second half of 2021. Information was collected on the following topics: sociodemographic and socioeconomic status; type of travel and previous travel experience; health status and risk perception (of COVID-19 and tropical infectious diseases). Using all features simultaneously, an unsupervised machine learning approach (k-means) is implemented to characterize groups of travelers. Pairwise chi-squared tests were performed to identify key features that showed statistically significant differences between clusters.

RESULTS

The travelers were clustered into seven groups. We associated the clusters with different intensities of perceived risk of acquiring COVID-19 and tropical infectious diseases on the trip. The perceived risk of both diseases was low in the group "middle or lower middle class young inexperienced male tourist" but high in the group "middle or lower middle-class young with children inexperienced business traveler".

CONCLUSIONS

Broadening our knowledge of the profiles of travelers to intermediate-high health risk areas would help to tailor the health advice provided by practitioners to their characteristics and type of travel. In a changing health context, the k-means approach supposes a flexible statistical method that calculates travelers' profiles and can be easily adapted to process new information.

Understanding the Barriers and Attitudes toward Influenza Vaccine Uptake in the Adult General Population: A Rapid Review

Influenza is a common respiratory infection associated with a substantial clinical, humanistic, and economic burden globally. Vaccines are essential to prevent and control influenza and are recommended by public-health agencies, such as the WHO and US CDC; however, vaccination rates vary considerably across the globe. This review aimed to investigate the perceived barriers and attitudes to influenza vaccination in the global population, in order to identify strategies that may improve influenza vaccination coverage. A structured literature search was undertaken to identify studies that reported on patient-reported attitudes towards influenza vaccination, focused on the adult general population in 16 prespecified countries. Eighty studies were included in this review. Negative attitude towards healthcare were found to be the most agreed upon barrier to vaccine uptake (31.1% agreement). The most agreed promoter of influenza vaccination was trust in healthcare services (62.0% agreement). Approximately 50% of participants intended to receive the influenza vaccine in the following season. To improve influenza vaccination coverage, healthcare workers must strengthen the foundation of substantial trust in healthcare services and provide educational materials that improve influenza vaccination knowledge among the adult general population.

Safety profile comparison of chimeric live attenuated and Vero cell-derived inactivated Japanese encephalitis vaccines through an active surveillance system in Australia

Limited information is available about post-marketing safety of Japanese encephalitis (JE) vaccines. Using data from SmartVax, an active surveillance system for monitoring vaccine safety, adverse events following immunizations (AEFIs) were compared between the two JE vaccines available in Australia (a chimeric live attenuated vaccine [Imojev] and a Vero cell-derived inactivated vaccine [JEspect]). Data from 2756 patients (1855 Imojev and 901 JEspect) were included. Overall (7.0%), systemic (2.8%), and local (1.9%) AEFIs were uncommon. There were no significant differences in the odds of overall (OR = 1.27; 95%CI: 0.91–1.77), systemic (OR = 1.23; 95%CI: 0.74–2.06), or local (OR = 1.20; 95%CI: 0.65–2.22) AEFIs with Imojev compared to JEspect. There was an increase in odds of overall AEFI in patients aged <5 years (OR = 2.39; 95%CI: 1.10–5.19) compared to those aged >50 years. Both JE vaccines available in Australia are safe and well tolerated. Odds of AEFIs were age-dependent, young children should be carefully observed for AEFIs after vaccination.

Characteristics and potential quality indicators for evaluating pre-travel consultations in Japan hospitals: the Japan Pretravel consultation registry (J-PRECOR)

Background

Awareness of pre-travel consultations (PTCs) and prevention methods for overseas travel-related diseases, and the understanding of PTCs among Japanese travelers and medical professionals remains low in Japan. A multicenter registry was established to examine PTCs in Japan. This study assessed the PTC implementation rate and examined the indicators of PTCs that can be used as criteria for evaluating quality.

Methods

Clients who presented for their PTCs at 17 facilities and were registered between February 1, 2018, and May 31, 2020, were included. Medical information was extracted retrospectively via a web-based system. Correlations between vaccination risk categories and advice/intervention proportions by the facility were evaluated using Spearman’s ordered phase relations (α = 0.05).

Results

Of the 9700 eligible clients (median age, 32 years; 880 [9.1%] aged < 16 years and 549 [5.7%] aged ≥65 years), the most common travel duration was ≥181 days (35.8%); higher among younger clients. The most common reason for travel was business (40.5%); the US (1118 [11.5%]) and Asia (4008 [41.3%]) were the most common destinations and continents, respectively. The vaccine number (median three per person) increased after the PTCs except for the tetanus toxoid. Only 60.8% of the clients recommended for malaria prophylaxis received anti-malarial agents. The gross national income; the incidence of human rabies, typhoid fever, falciparum malaria; and dengue risk category were associated with the percentage of hepatitis-A vaccines; explaining rabies post-exposure prophylaxis, typhoid-fever vaccinations, malaria-prophylaxis prescriptions; and mosquito repellants, respectively.

Conclusions

Although the characteristics of the travelers differed, the quality of the PTCs should be improved to address, for example, the lower rate of acceptance of malaria prophylaxis in Japan.

Supplementary Information

The online version contains supplementary material available at 10.1186/s40794-021-00160-4.

Immunogenicity of a single fractional intradermal dose of Japanese encephalitis live attenuated chimeric vaccine

BACKGROUND

Japanese encephalitis (JE) is endemic in Asia and the western Pacific. Vaccination is recommended for travellers to endemic regions, but the high cost of the vaccine is a major barrier to uptake.

METHODS

A quasi-experimental, pre-post intervention clinical trial without a control group was conducted to assess the immunogenicity and safety of intradermal (ID) JE vaccine. Healthy adults (18-45 years) received one dose of 0.1 mL (20% of standard dose) ID Imojev® (JE live attenuated chimeric vaccine, Sanofi-Aventis). Adverse events following immunisation (AEFIs) were recorded 10 days post-vaccination. Blood samples were collected at baseline, 4, and 8 weeks post-vaccination. Neutralising antibodies were measured using 50% plaque reduction neutralisation test (PRNT50). Seroconversion was defined as PRNT50 titre ≥10. An in vitro study was also conducted to quantify the rate of decay of vaccine potency after reconstitution.

RESULTS

51 participants (72.6% females, median age 31 years), all non-reactive to JE virus at baseline were enrolled. Mild and moderate AEFIs were reported by 19.6% of participants; none required medical attention or interfered with normal daily activities. All participants seroconverted at 4 weeks (GMT 249.3; 95%CI:192.8-322.5) and remained seropositive at 8-weeks (GMT 135.5; 95%CI:104.5-175.6). Vaccine potency declined at a rate of 0.14 log plaque-forming units/0.5 mL per hour.

CONCLUSIONS

In healthy adults, a single 0.1 mL ID dose of Imojev was safe and immunogenic, at least in the short-term. Reconstituted vials of Imojev vaccine may not retain their potency after 6 hours. Fractional JE ID vaccination could be a cheaper yet effective alternative for short-term travellers. Further studies need to investigate the immune response in a wider age range of individuals and the long-term immunogenicity of fractional JE ID vaccines.

CLINICAL TRIALS REGISTRATION

ACTRN12621000024842.

Temporal Trend of COVID-19 Vaccine Acceptance and Factors Influencing International Travellers

The COVID-19 pandemic has seen disrupted international travel due to travel restrictions and public health measures aimed at containing the spread of the virus. With increasing evidence of the COVID-19 vaccines' ability to mitigate disease severity, reopening tourism is desirable to promote the recovery of the global economy. However, the COVID-19 vaccine and vaccination passport for international travellers remains an ongoing debate. Little is known of the acceptance of these and the influencing factors among this population group. Therefore, this study sought to determine the temporal trend in COVID-19 vaccine acceptance and influencing factors among international travellers. A cross-sectional study was conducted using a self-administered questionnaire among international travellers who visited the Thai Travel Clinic, Hospital for Tropical Diseases, Mahidol University, Thailand from June 2021 to December 2021 (3 different variants dominated during this period). Study data were analyzed using SPSS software, version 23. Chi-square was used to demonstrate associations. Binary logistic regression was used to evaluate the magnitude of effect, demonstrated by odds ratio with 95% confidence interval. All significant variables were included in a multinomial logistic regression model to estimate adjusted odds ratios. The study enrolled 1068 travellers, 719 (67.3%) Thai and 349 (32.7%) foreign travellers. Most travellers were female (55.4%) and aged 18-30 years. The three main purposes for visiting the clinic were: for study, visiting friends and relatives, and returning to their home country. The overall COVID-19 vaccine acceptance rate among the travellers was 96.2%. The temporal trend of acceptance among Thai and non-Thai travelers varied from 93-99% and 93-100%, respectively. Vaccine efficacy, protective duration of the vaccine, risk of infection, and travel plan were factors strongly associated with COVID-19 vaccine acceptance. In conclusion, the COVID-19 vaccine acceptance rate among these international travellers was very high. The safe and effective reopening of tourism to international travellers will facilitate economic recovery.

Using social media listening and data mining to understand travellers' perspectives on travel disease risks and vaccine-related attitudes and behaviours

BACKGROUND

Travellers can access online information to research and plan their expeditions/excursions, and seek travel-related health information. We explored German travellers' attitude and behaviour toward vaccination, and their travel-related health information seeking activities.

METHODS

We used two approaches: web 'scraping' of comments on German travel-related sites and an online survey. 'Scraping' of travel-related sites was undertaken using keywords/synonyms to identify vaccine- and disease-related posts. The raw unstructured text extracted from online comments was converted to a structured dataset using Natural Language Processing Techniques. Traveller personas were defined using K-means based on the online survey results, with cluster (i.e. persona) descriptions made from the most discriminant features in a distinguished set of observations. The web-scraped profiles were mapped to the personas identified. Travel and vaccine-related behaviours were described for each persona.

RESULTS

We identified ~2.6 million comments; ~880 k were unique and mentioned ~280 k unique trips by ~65 k unique profiles. Most comments were on destinations in Europe (37%), Africa (21%), Southeast Asia (12%) and the Middle East (11%). Eight personas were identified: 'middle-class family woman', 'young woman travelling with partner', 'female globe-trotter', 'upper-class active man', 'single male traveller', 'retired traveller', 'young backpacker', and 'visiting friends and relatives'. Purpose of travel was leisure in 82-94% of profiles, except the 'visiting friends and relatives' persona. Malaria and rabies were the most commented diseases with 12.7 k and 6.6 k comments, respectively. The 'middle-class family woman' and the 'upper-class active man' personas were the most active in online conversations regarding endemic disease and vaccine-related topics, representing 40% and 19% of comments, respectively. Vaccination rates were 54%-71% across the traveller personas in the online survey. Reasons for vaccination reluctance included perception of low risk to disease exposure (21%), price (14%), fear of side effects (12%) and number of vaccines (11%).

CONCLUSIONS

The information collated on German traveller personas and behaviours toward vaccinations should help guide counselling by healthcare professionals.

Travel vaccination examined through the tourism lens

Travel vaccination hesitancy—a shared concern of travel medicine and tourism.

Drivers of the summer influenza epidemic in New South Wales, 2018-19

OBJECTIVES

To assess the extent to which the 2018-19 New South Wales summer influenza epidemic was associated with overseas or domestic travel and with seasonal influenza vaccination status.

DESIGN, SETTING

Unmatched case-control study, based on an online survey distributed from the NSW Notifiable Conditions Information Management System (NCIMS) to people for whom mobile phone numbers were available.

PARTICIPANTS

A case was defined as a person with notified laboratory-confirmed influenza with onset of illness between 1 December 2018 and 21 March 2019. People with notified pertussis infections (confirmed or probable) were selected as controls.

MAIN OUTCOME MEASURES

Notified influenza infection, by travel and contact with unwell overseas travellers in the week before onset of illness and seasonal influenza vaccination status (as the primary exposures).

RESULTS

Valid survey responses were provided by 648 of 2806 invited people with notified influenza (23%) and 257 of 796 invited people with notified pertussis (32%). The demographic characteristics of the respondents were similar to those of the source population (7251 cases, 2254 controls). During the first two months of the summer of 2018-19, notified influenza was more likely for people who had travelled overseas or had contact with an ill overseas traveller in the week before symptom onset (adjusted OR [aOR], 6.99; 95% CI, 3.59-13.6), but not during the second two months (aOR, 1.63; 95% CI, 0.79-3.35). Influenza vaccination status was not associated with the likelihood of notified influenza.

CONCLUSIONS

Travel-related factors were early drivers of the 2018-19 NSW summer influenza epidemic; local transmission sustained the outbreak despite unfavourable conditions later in summer. Our findings prompted re-evaluation of recommendations for pre-travel vaccination in NSW. The role of travel in out-of-season influenza outbreaks should be considered in other temperate zones.

Efficacy of one-dose intramuscular rabies vaccine as pre-exposure prophylaxis in travellers

BACKGROUND

Current guidelines for rabies pre-exposure prophylaxis (PrEP) recommend multiple vaccine doses. Travellers sometimes present for pre-travel consultation with insufficient time to complete standard PrEP schedules. We investigated the efficacy of one-dose intramuscular (IM) vaccine in priming the immune system (as PrEP) by measuring antibody response to simulated post-exposure prophylaxis (PEP).

METHODS

A quasi-experimental pre-post intervention clinical trial was conducted at a specialist travel clinic in Australia. Adults (≥18 years) without a history of rabies vaccination were included. At Visit 1, seronegative status was confirmed and one dose of 0.5 ml IM rabies vaccine (Verorab®) administered. At Visit 2 (≥60 days after Visit 1), serology was repeated and a simulated PEP dose (0.5 ml IM) given on this day and again 3 days later (Visit 3). Serology was repeated at Visit 4 (7 days after Visit 2).

RESULTS

A total of 94 antibody-negative participants were included (<50 years [n = 50]; ≥50 years [n = 44]). At Visit 2, 38.0 and 31.8% of participants aged <50 and ≥50 years were antibody-positive (≥0.5 EU/ml). At Visit 4, all participants were antibody-positive; 82.0 and 47.7% of participants aged <50 and ≥50 years had antibody levels >4 EU/ml, respectively.

CONCLUSIONS

One-dose IM vaccine was effective as PrEP for priming the immune system in both age groups, resulting in rapid development of antibodies 7 days after commencing simulated PEP. If there is insufficient time to complete a standard PrEP schedule, one-dose IM could be considered as an alternative schedule for short trips, rather than not offering travellers any doses at all.Clinical trials registration: ACTRN12619000946112.

Comparison of immunogenicity and safety of licensed Japanese encephalitis vaccines: A systematic review and network meta-analysis

INTRODUCTION

Annually more than 100,000 Japanese encephalitis (JE) cases and 25,000 deaths worldwide are caused by JE virus infection. More than 15 JE vaccines are currently in use worldwide. It is unknown whether any of the vaccines is superior to the others in terms of immunogenicity and safety.

METHODS

Four databases were systematically searched for randomised controlled trials that compared two or more types of JE vaccines. Vaccines were classified into four classes: inactivated mouse brain-derived (oldest class), inactivated Vero cell, live chimeric, and live attenuated. Network meta-analysis was used to generate mixed effect estimates against inactivated mouse brain-derived vaccines for seroconversion, and against placebo for adverse event (AE) and severe adverse event (SAE).

RESULTS

23 studies (38,496 participants) were included. All newer vaccine classes had better immunogenicity, the difference was statistically significant for inactivated Vero cell (OR = 2.98; 95 %CI: 1.02-8.65) and live chimeric (OR = 5.93; 95 %CI: 1.73-20.32) vaccines. Inactivated mouse-derived vaccines had the highest odds for AEs (OR = 2.27; 95 %CI: 1.59-3.23), the odds of AE of newer vaccines was not different to placebo. There was no difference in SAEs across vaccine classes.

CONCLUSIONS

All newer JE vaccines have comparable safety profiles, live chimeric and inactivated Vero cell vaccines are the most immunogenic among the newer vaccine classes.

Beyond fragmentary: A proposed measure for travel vaccination concerns

The travel medicine literature points to travelers' concerns as significant promoters of their under-vaccinations. Therefore, this study researches the hitherto understudied concept of vaccination concern and its theoretical scope in the international travel space. It attempts a conceptualization of the concept by delimiting its theoretical scope and proposes a measure for it. An exploratory sequential mixed-methods design was used to conduct four interlocking studies using data from a netnography, field interviews, and surveys among varied international travelers. A scale with six dimensions, comprising safety, efficacy, cost, time, access, and autonomy concerns were revealed. The scale significantly explained mainstream and segments-based tourists' uptake attitudes and behavior for their eligible vaccines. The findings suggest that anti-travel vax sentiments and public vax sentiments despite conceptually similar are considerably distinct. The broad nature of the scale and its prediction of travelers' vaccine uptake make it clinically relevant for tracking and resolving concerns for increased vaccine uptake.

A Normative Behavior of Pre-Travel Health Consultation and the Associated Factors among Travelers

Introduction: Travelers may transmit diseases due to their behavior of travel, consequently travelers should consider preventive measurement through pre-travel health consultation seeking behavior. Pre-travel health consultation is a particular preparation ideally conducted by international travelers to obtain risk assessment and management to prevent the transmission of diseases. This study investigates the relationship of socio-demographic characteristics and itinerary on pre-travel health consultation behavior among international travelers in Badung, Bali.Methods: A descriptive-correlative design using a cross-sectional approach employed 125 participants determined by a purposive sampling technique performed in the ten tourist destinations of Badung Regency. Data collection was conducted on February 15th until March 5th, 2020. Data demography, travel plan, and anonymous questionnaires regarding pre-travel health consultation behavior are used in this research. The Gamma coefficient correlation and Kruskal-Wallis statistic tests were performed in the study for bivariate analysis.Results: The results showed that age (p<0.0001; r=-0.650) and past-travel history to Bali (p=0.004; r=-0.475) were significantly correlated with pre-travel health consultation behavior among international travelers in Badung, Bali. Meanwhile sex, nationality, last education, travel duration, and types of the destination visited were not significantly associated with pre-travel health consultation behavior among international travelers in Badung, Bali (p>0.05).Conclusion: The age and past-travel history to Bali seem to be predictors for travelers to uptake pre-travel health consultation, thus nurses should be able to promote the implementation of pre-travel health consultation by utilizing the media promotion appropriately adjusted to the age of travelers and travel experience.

Travelers' Attitudes, Behaviors, and Practices on the Prevention of Infectious Diseases: A Study for Non-European Destinations

BACKGROUND

The aim of this study was to improve our comprehension of the attitudes, behaviors, and practices related to the health risks of travel to non-European destinations.

METHODS

This cross-sectional study utilized an online questionnaire disseminated through social networks.

RESULTS

About 79% of the respondents reported that they informed themselves or would inform themselves about travel-related health risks before departure. The most used sources of information were the Internet (52%) and health professionals (42%). Older age groups were positively associated with seeking pretravel health information (OR = 2.44, CI 95%: 1.18-5.01, in the age group 25-34 years and OR = 14.6, CI 95%: 1.77-119.50, in subjects over 65 years). Travelers visiting friends and relatives (VFRs) were less likely to seek health information (OR = 0.49; CI 95%: 0.26-0.95). About 13.9% of participants had doubts about the practice of vaccination. Those who sought information on social media had a higher probability of refusing vaccination (OR = 3.24; CI 95%: 1.02-10.19).

CONCLUSIONS

The data demonstrate that VFRs and the younger population are less informed about travel risks compared with other travelers. This study also revealed the importance that digital information assumes for travelers. Therefore, decisive efforts should be made to ensure that travelers can find correct and reliable information on the Web, particularly on social media.

Yellow Fever Vaccine Administration at Global TravEpiNet (GTEN) Clinics during a Period of Limited Vaccine Availability in the United States, 2017-2018

In 2016, Sanofi Pasteur (S-P) experienced a manufacturing disruption of yellow fever vaccine (YF-Vax), the only U.S.-licensed YF-Vax, depleting the U.S. supply by mid-2017. Sanofi Pasteur received approval to import Stamaril, S-P's French-manufactured YF-Vax, for use in 260 U.S. civilian clinics under an expanded access investigational new drug program (EAP). The CDC also broadened its YF-Vax indication in early 2018. Our objective was to assess usage at participating Global TravEpiNet (GTEN) clinics, a U.S. CDC-supported national consortium of clinical sites that administer vaccines, during this period of limited availability and changing recommendations. We analyzed 2012-2018 GTEN data for YF-Vax usage, unavailability, and reasons for refusal. We also performed a brief voluntary survey of GTEN sites to better understand their experience during the shortage. Yellow fever vaccine unavailability at certain GTEN clinics was intermittent and recurrent, starting months before total depletion. Unavailability at GTEN clinics peaked weeks before the total depletion. Compared with historic norms, YF-Vax usage following initial vaccine availability limitations did not change until vaccine recommendations were broadened. Refusal of recommended YF-Vax also decreased during this period. Queried sites participating in the EAP felt their supply of vaccine was adequate. Our analysis suggests that in response to depletion of a travel vaccine, an EAP can make an unlicensed product available, patients will participate in such a program, and the program can respond to expanding recommendations for vaccine usage.

Simplified rabies pre-exposure prophylaxis in last-minute travellers

Less can be more: simplified two-visit rabies pre-exposure prophylaxis once in a lifetime will certainly increase compliance in last-minute travellers and ease the post-exposure procedures after animal risks in endemic countries. Different arguments are being put forward to shorten this vaccination scheme even further into an effective one-day scheme.

Rabies vaccination strategies in the Netherlands in 2018: a cost evaluation

BackgroundThe risk of contracting rabies is low for travellers. However, the number of Dutch travellers potentially exposed abroad following an animal-associated injury and needing post-exposure prophylaxis (PEP) has increased, resulting in increased costs.AimHere, we evaluated the costs and the cost-effectiveness of different pre- and post-exposure interventions in the Netherlands, taking into account the 2018 World Health Organization (WHO) recommendations for the prevention of rabies.MethodsA decision tree-based economic model was constructed. We calculated and compared the cost of different WHO pre-exposure prophylaxis (PrEP) recommendations, intramuscular vs intradermal vaccination and PEP subsequent to increased vaccination coverage in risk groups. We estimated cost-effectiveness, expressed as incremental costs per rabies immunoglobulin (RIG) administration averted, using a societal perspective. Statistical uncertainty regarding number of travellers and vaccination coverage was assessed.ResultsTotal costs at the national level were highest using previous WHO recommendations from 2012, estimated at EUR 15.4 million annually. Intradermal vaccinations in combination with the current recommendations led to the lowest costs, estimated at EUR 10.3 million. Higher vaccination uptake resulted in higher overall costs. The incremental costs per RIG administration averted varied from EUR 21,300-46,800.ConclusionsThe change in rabies PrEP and PEP recommendations in 2018 reduced total costs. Strategies with increased pre-travel vaccination uptake led to fewer RIG administrations and fewer vaccinations after exposure but also to higher total costs. Although larger scale intradermal administration of rabies vaccine can reduce total costs of PrEP and can positively influence vaccination uptake, it remains a costly intervention.

Surveying Health-Related Knowledge, Attitudes, and Behaviors of U.S.-Based Residents Traveling Internationally to Visit Friends and Relatives

U.S. residents traveling internationally to regions with increased risk of infectious diseases infrequently seek pretravel health care. First- and second-generation immigrants traveling to their countries of origin and visiting friends and relatives (VFRs) have increased risk of certain infectious diseases and are more likely to participate in high-risk activities. In an online survey of 994 U.S. residents with two foreign-born parents who went on at least one international trip to an at-risk country (defined as having a typhoid vaccine recommendation) in the prior 3 years, respondents were questioned about their international travel over the previous 3 years and their knowledge and individual risk of disease. Participants reported infrequently seeking pretravel health information (32% of trips) or consulting a healthcare provider before their trips (15% of trips). Participants reported seeking pretravel health information less often for VFR trips home (22%) than to other regions (30%). Perceived risk of disease was directly associated with seeking pretravel health information (82% for the highest and 13% for the lowest perceived risk), consulting a healthcare provider (55% for the highest and 5% for the lowest perceived risk), and reporting travel-associated illness (54% for the highest and 10% for the lowest perceived risk). Respondents were generally knowledgeable about cholera, hepatitis B, malaria, and rabies but had low knowledge of hepatitis A and typhoid. Understanding where VFR travelers lack understanding of disease transmission and which travelers are ideal targets for interventions has the potential to shape physician recommendations and public health strategy in this vulnerable population.

Determinants of Vaccination Uptake in Risk Populations: A Comprehensive Literature Review

Vaccination uptake has decreased globally in recent years, with a subsequent rise of vaccine-preventable diseases. Travellers, immunocompromised patients (ICP), and healthcare workers (HCW) are groups at increased risk for (severe) infectious diseases due to their behaviour, health, or occupation, respectively. While targeted vaccination guidelines are available, vaccination uptake seems low. In this review, we give a comprehensive overview of determinants-based on the integrated change model-predicting vaccination uptake in these groups. In travellers, low perceived risk of infection and low awareness of vaccination recommendations contributed to low uptake. Additionally, ICP were often unaware of the recommended vaccinations. A physician's recommendation is strongly correlated with higher uptake. Furthermore, ICP appeared to be mainly concerned about the risks of vaccination and fear of deterioration of their underlying disease. For HCW, perceived risk of (the severity of) infection for themselves and for their patients together with perceived benefits of vaccination contribute most to their vaccination behaviour. As the determinants that affect uptake are numerous and diverse, we argue that future studies and interventions should be based on multifactorial health behaviour models, especially for travellers and ICP as only a limited number of such studies is available yet.

Prescribing Patterns of Antibiotics for the Self-Treatment of Travelers' Diarrhea in Global TravEpiNet, 2009-2018

Background

International travelers are often prescribed antibiotics for self-treatment of travelers' diarrhea (TD), but the benefits and risks of antibiotics are debated. We assessed the prescribing patterns of empiric antibiotics for TD in international travelers evaluated at Global TravEpiNet (GTEN) sites (2009-2018).

Methods

We performed a prospective, multisite cross-sectional study regarding antibiotic prescriptions for the self-treatment of TD at 31 GTEN sites providing pretravel consultations to adult international travelers. We described traveler demographics, itineraries, and antibiotic(s) prescribed. We used multivariable logistic regressions to assess the association of year of consultation with antibiotic prescribing (yes/no) and class (fluoroquinolones vs azithromycin). We performed interrupted time-series analyses to examine differences in prescribing before and after the Food and Drug Administration (FDA) warning on fluoroquinolones (July 2016).

Results

Antibiotics were not prescribed in 23 096 (22.2%) of 103 843 eligible pretravel GTEN consultations; azithromycin and fluoroquinolones were most frequently prescribed. Antibiotic prescribing declined significantly each year between 2009 and 2018 (odds ratio [OR], 0.84; 95% CI, 0.79-0.89), as did fluoroquinolone prescribing, relative to azithromycin (OR, 0.77; 95% CI, 0.73-0.82). The rate of decline in fluoroquinolone prescribing was significantly greater after the FDA fluoroquinolone warning (15.3%/year) than before (1.1%/year; P < .001).

Conclusions

Empiric antibiotics for TD were prescribed in >75% of pretravel GTEN consultations, but antibiotic prescribing declined steadily between 2009 and 2018. Fluoroquinolones were less frequently prescribed than azithromycin, especially after the 2016 FDA fluoroquinolone warning. Emphasis on the risks of antibiotics may influence antibiotic prescribing by providers for empiric treatment of TD.

Serum chymase levels correlate with severe dengue warning signs and clinical fluid accumulation in hospitalized pediatric patients

Dengue induces a spectrum of severity in humans from the milder dengue fever to severe disease, or dengue hemorrhagic fever (DHF). Chymase is a candidate biomarker that may aid dengue prognosis. This prospective study aimed to identify whether warning signs of severe dengue, including hypovolemia and fluid accumulation, were associated with elevated chymase. Serum chymase levels were quantified prospectively and longitudinally in hospitalized pediatric dengue patients in Sri Lanka. Warning signs were determined based on daily clinical assessments, laboratory tests and ultrasound findings. Chymase was significantly elevated during the acute phase of disease in DHF or Severe dengue, defined by either the 1997 or 2009 WHO diagnosis guidelines, and persisted longer in the most severe patients. Chymase levels were higher in patients with narrow pulse pressure and clinical warning signs such as severe leakage, fluid accumulation, pleural effusion, gall-bladder wall thickening and rapid haematocrit rise concurrent with thrombocytopenia. No association between chymase and liver enlargement was observed. This study confirms that serum chymase levels are associated with DHF/Severe dengue disease in hospitalized pediatric patients. Chymase levels correlate with warning signs of vascular dysfunction highlighting the possible functional role of chymase in vascular leakage during dengue.

The Traveller's Risk Perception (TRiP) questionnaire: pre-travel assessment and post-travel changes

BACKGROUND

Travellers' risk perception is a key component of travel risk assessment because it influences the adequate implementation of safety precautions. The aims of this study are to validate a tool to analyse travellers' risk perception to identify which factors can influence it and how it changes upon return.

METHODS

The Traveller's Risk Perception (TRiP) questionnaire was developed and administered to outpatients before and after travel in three travel clinics. A principal component analysis (PCA) was performed to validate the questionnaire and multivariate regression analysis was used to evaluate the effect of travellers' characteristics on the risk scores.

RESULTS

A total of 1020 travellers completed the questionnaire. PCA identified two latent factors: 'generic-disseminated risks' and 'specific-circumstantial risks'. Cronbach's α was acceptable (0.76 and 0.70, respectively). The 'generic-disseminated risks' dimension scored higher than the 'specific-circumstantial risks' (p<0.001). The items with the highest scores were insect bites, gastrointestinal disorders and malaria. The mean scores were significantly lower after the travel for all items but one.

CONCLUSIONS

The TRiP questionnaire is a valid and reliable tool for rating travellers' perceptions. Staff in travel clinics should be trained to systematically assess travellers' risk perception in order to tailor the consultation according to specific information needs.

[Travel vaccinations for certain groups of persons]

The number of international travelers has been continuously increasing in recent decades. Among travelers, there are more and more people at an increased risk for acquiring diseases that could be prevented by vaccines or for the development of a severe course of disease. Risk groups in travel medicine are senior travelers, children, pregnant and breast-feeding women, persons with pre-existing medical conditions, and persons who visit their friends and relatives abroad (VFR). Individuals in these groups require attention during pretravel advice consultations, particularly with regards to recommended vaccinations. On the other hand, for some risk groups, particular vaccines cannot be given for safety reasons or because the response to vaccines is reduced. Not all risk groups or each vaccine have sufficient evidence available, so each patient's risks and benefits must be weighed during pretravel consultation. In this article, the particularities for each risk group with respect to pretravel immunization are highlighted.

Spread of Measles in Europe and Implications for US Travelers

From January 2018 to June 2018, World Health Organization (WHO) European Region countries reported >41 000 measles cases, including 37 deaths, a record high since the 1990s. Low vaccination coverage in previous years is the biggest contributing factor to the increase in cases. The Ukraine reported the majority of cases, but France, Georgia, Greece, Italy, the Russian Federation, and Serbia also reported high case counts. Europe is the most common travel destination worldwide and is widely perceived as being without substantial infectious disease risks. For this reason, travelers may not consider the relevance of a pretravel health consultation, including vaccination, in their predeparture plans. Measles is highly contagious, and the record number of measles cases in the WHO European Region not only puts unvaccinated and inadequately vaccinated travelers at risk but also increases the risk for nontraveling US residents who come into close contact with returned travelers who are ill. The US Centers for Disease Control and Prevention encourage US travelers to be aware of measles virus transmission in Europe and receive all recommended vaccinations, including for measles, before traveling abroad. Health care providers must maintain a high degree of suspicion for measles among travelers returning from Europe or people with close contact with international travelers who present with a febrile rash illness. The current WHO European Region outbreak should serve to remind health care providers to stay current with the epidemiology of highly transmissible diseases, such as measles, through media, WHO, and Centers for Disease Control and Prevention reports and encourage measles vaccination for international travelers.

Perceptions of rabies risk: a survey of travellers and travel clinics from Canada, Germany, Sweden and the UK

BACKGROUND

Extensive global experience shows that rabies pre-exposure prophylaxis (PrEP) through vaccination is effective and well tolerated, yet many travellers opt not to be vaccinated when travelling to rabies-endemic countries. Previous research has identified several factors influencing the choices travellers make to reduce the risk of rabies, including cost, time constraint and perspective on the importance of vaccination. The objectives of this study were to assess travellers' awareness of rabies and advice-seeking attitudes and to evaluate travel clinics practices regarding rabies pre-travel advice.

METHODS

We surveyed individuals aged 18-65 years residing in the UK, Germany, Canada and Sweden who had travelled to rabies-endemic countries between 2013 and 2016 and defined this as the rabies visit-risk sample. The first 850 respondents from the visit-risk sample who had undertaken pre-defined at-risk activities (e.g. contact with animals during the trip) completed an additional 15-min online questionnaire and were included in the activity-risk subsample. We also interviewed travel clinic personnel using a 25-min online or phone questionnaire.

RESULTS

The visit-risk sample included 4678 individuals. Many sought pre-travel health information online (33%) or talked to a family doctor (24%). Within the activity-risk subsample, 83% of travellers were aware of at least a few basic facts about rabies, and 84% could identify at least one correct rabies prevention measure; 49% were aware of a rabies vaccine, however, only 8% reported receiving PrEP vaccination within the past 3 years. Among 180 travel clinic respondents, 21% reported recommending PrEP against rabies to all travellers to rabies-endemic countries. Travel clinics estimated that 81% of travellers complete their travel vaccination schedules and reported sending reminders by e-mails (38%), text (38%), phone calls (37%) or by using vaccination cards (37%).

CONCLUSIONS

These findings suggest that although travellers had frequently heard of rabies, awareness of the risks of this serious infectious disease was relatively low. 5975671594001tay062media15975671594001.

Globalization and the Changing Epidemiology of Hepatitis A Virus

Increased economic interdependence, social integration, and other aspects of globalization are contributing to significant changes in hepatitis A epidemiology. Globally, the incidence of hepatitis A virus (HAV) infection is decreasing, the age at midpoint of population immunity (AMPI) is increasing, and the proportion of symptomatic cases is increasing as the average age at infection increases. In low-income countries, HAV remains endemic but improved water and sanitation systems are reducing transmission rates among young children. In high-income countries, most adults remain susceptible to HAV and foodborne outbreaks are becoming more frequent. Middle-income countries have diverse epidemiological profiles, and they play important roles in the global spread of HAV through international trade and travel. Future changes in the epidemiology of hepatitis A will be heavily influenced by globalization processes.

Willingness to pay for an Ebola vaccine during the 2014-2016 ebola outbreak in West Africa: Results from a U.S. National sample

The 2014-2016 Ebola virus outbreak in West Africa led to advances in the development of vaccines against Ebola. This study examined factors associated with willingness to pay for an Ebola vaccine among a U.S. national sample during the recent Ebola outbreak. From April 30-May 8, 2015, a national survey was conducted using the GfK Group's KnowlegePanel®. Main outcome measures included willingness to pay at least $1; more than $50; and more than $100 for an Ebola vaccine. Analyses were conducted using weighted multivariable logistic regression. Among participants (N = 1,447), 583 (40.3%) would not pay for an Ebola vaccine; 864 (59.7%) would pay at least $1. Among those willing to pay at least $1: 570 (66.0%) would pay $1-50; 174 (20.1%) would pay $51-100; and 120 (13.9%) would pay more than $100. Willingness to pay at least $1 for an Ebola vaccine was associated with international travel; interest in getting an Ebola vaccine; and beliefs that the U.S. government should spend money to control Ebola and assume worldwide leadership in confronting emerging epidemics. Willingness to pay more than $50 was associated with similar variables. Willingness to pay more than $100 was associated with international travel; interest in getting an Ebola vaccine; information seeking; and beliefs that the U.S. government should assume worldwide leadership in confronting emerging epidemics. International travel and interest in an Ebola vaccine were key predictors of willingness to pay across all price points. Understanding willingness to pay for vaccines against emerging infectious diseases remains critical.

Illness among US resident student travellers after return to the USA: a GeoSentinel analysis, 2007-17

Background

The number of US students studying abroad more than tripled during the past 20 years. As study abroad programmes' destinations diversify, students increasingly travel to resource-limited countries, placing them at risk for infectious diseases. Data describing infections acquired by US students while travelling internationally are limited. We describe illnesses among students who returned from international travel and suggest how to prevent illness among these travellers.

Methods

GeoSentinel is a global surveillance network of travel and tropical medicine providers that monitors travel-related morbidity. This study included the records of US resident student international travellers, 17-24 years old, who returned to the USA, had a confirmed travel-related illness at one of 15 US GeoSentinel sites during 2007-17 and had a documented exposure region. Records were analysed to describe demographic and travel characteristics and diagnoses.

Results

The study included 432 students. The median age was 21 years; 69% were female. More than 70% had a pre-travel consultation with a healthcare provider. The most common exposure region was sub-Saharan Africa (112; 26%). Students were most commonly exposed in India (44; 11%), Ecuador (28; 7%), Ghana (25; 6%) and China (24; 6%). The median duration of travel abroad was 40 days (range: 1-469) and presented to a GeoSentinel site a median of 8 days (range: 0-181) after travel; 98% were outpatients. Of 581 confirmed diagnoses, the most common diagnosis category was gastrointestinal (45%). Acute diarrhoea was the most common gastrointestinal diagnosis (113 of 261; 43%). Thirty-one (7%) students had vector-borne diseases [14 (41%) malaria and 11 (32%) dengue]. Three had vaccine-preventable diseases (two typhoid; one hepatitis A); two had acute human immunodeficiency virus infection.

Conclusions

Students experienced travel-related infections, despite the majority having a pre-travel consultation. US students should receive pre-travel advice, vaccinations and chemoprophylaxis to prevent gastrointestinal, vector-borne, sexually transmitted and vaccine-preventable infections.

Missed Opportunities for Measles, Mumps, Rubella Vaccination Among Departing U.S. Adult Travelers Receiving Pretravel Health Consultations

Background

Measles outbreaks continue to occur in the United States and are mostly due to infections in returning travelers.

Objective

To describe how providers assessed the measles immunity status of departing U.S. adult travelers seeking pretravel consultation and to assess reasons given for nonvaccination among those considered eligible to receive the measles, mumps, rubella (MMR) vaccine.

Design

Observational study in U.S. pretravel clinics.

Setting

24 sites associated with Global TravEpiNet (GTEN), a Centers for Disease Control and Prevention-funded consortium.

Patients

Adults (born in or after 1957) attending pretravel consultations at GTEN sites (2009 to 2014).

Measurements

Structured questionnaire completed by traveler and provider during pretravel consultation.

Results

40 810 adult travelers were included; providers considered 6612 (16%) to be eligible for MMR vaccine at the time of pretravel consultation. Of the MMR-eligible, 3477 (53%) were not vaccinated at the visit; of these, 1689 (48%) were not vaccinated because of traveler refusal, 966 (28%) because of provider decision, and 822 (24%) because of health systems barriers. Most MMR-eligible travelers who were not vaccinated were evaluated in the South (2262 travelers [65%]) or at nonacademic centers (1777 travelers [51%]). Nonvaccination due to traveler refusal was most frequent in the South (1432 travelers [63%]) and in nonacademic centers (1178 travelers [66%]).

Limitation

These estimates could underrepresent the opportunities for MMR vaccination because providers accepted verbal histories of disease and vaccination as evidence of immunity.

Conclusion

Of U.S. adult travelers who presented for pretravel consultation at GTEN sites, 16% met criteria for MMR vaccination according to the provider's assessment, but fewer than half of these travelers were vaccinated. An increase in MMR vaccination of eligible U.S. adult travelers could reduce the likelihood of importation and transmission of measles virus.

Primary Funding Source

Centers for Disease Control and Prevention, National Institutes of Health, and the Steve and Deborah Gorlin MGH Research Scholars Award.