Implementation strategies for the first licensed dengue vaccine: A meeting report

Precision arbovirus serology with a pan-arbovirus peptidome

Arthropod-borne viruses represent a crucial public health threat. Current arboviral serology assays are either labor intensive or incapable of distinguishing closely related viruses, and many zoonotic arboviruses that may transition to humans lack any serologic assays. In this study, we present a programmable phage display platform, ArboScan, that evaluates antibody binding to overlapping peptides that represent the proteomes of 691 human and zoonotic arboviruses. We confirm that ArboScan provides detailed antibody binding information from animal sera, human sera, and an arthropod blood meal. ArboScan identifies distinguishing features of antibody responses based on exposure history in a Colombian cohort of Zika patients. Finally, ArboScan details epitope level information that rapidly identifies candidate epitopes with potential protective significance. ArboScan thus represents a resource for characterizing human and animal arbovirus antibody responses at cohort scale.

Effectiveness of mass dengue vaccination with CYD-TDV (Dengvaxia®) in the state of Paraná, Brazil: integrating case-cohort and case-control designs

Background

CYD-TDV (Dengvaxia®) was the first dengue vaccine approved, launched in Brazil in 2015 for individuals aged 9-44 years. We aimed to estimate the effectiveness of CYD-TDV in preventing symptomatic dengue cases during a campaign targeting individuals aged 15-27 years in selected municipalities in Paraná, Brazil. Additionally, we examined whether a history of dengue, as recorded by the surveillance system, modified the vaccine's effectiveness.

Methods

We conducted a case-cohort analysis comparing the frequency of vaccination, with at least one dose of CYD-TDV, in individuals with dengue confirmed by RT-PCR, identified by the surveillance system during 2019 and 2020, with the vaccination coverage in the target population. Moreover, in a case-control design using weighted controls, we assessed the documented history of dengue as a modifier of the vaccine's effectiveness. We used a logistic random-effects regression model, with data clustered in municipalities and incorporating covariates such as the incidence of dengue before the campaign, age, and sex. We calculated vaccine effectiveness (VE) as (1-relative risk) x 100%.

Findings

1869 dengue cases were identified, which had a vaccination frequency significantly lower than the overall vaccination coverage in the target population (50.3% vs. 57.2%, respectively; overall VE: 21.3%; 95% confidence interval [CI]: 13.4%-28.4%). In individuals with a documented history of dengue, vaccination had a VE of 71% (95% CI: 58%-80%) in reducing the incidence of dengue. However, vaccination was not associated with a significant reduction in the overall dengue case risk in individuals without a documented history of dengue (VE: 12%; 95% CI: -21% to 36%). In this last stratum, vaccination was associated with reduced cases due to DENV-1 and DENV-4, but an excess of DENV-2 cases.

Interpretation

Vaccination led to a significant reduction in reported dengue cases within the target population. The case-control design suggested that this reduction was primarily driven by the benefits observed in individuals with a documented history of dengue. In endemic regions with limited serological testing facilities, a previous history of dengue diagnosis recorded by epidemiological surveillance could be used to triage candidates for CYD-TDV vaccination.

Funding

Research supported by Sanofi.

Heterologous prime-boost immunization induces protection against dengue virus infection in cynomolgus macaques

IMPORTANCE

Currently licensed dengue vaccines do not induce long-term protection in children without previous exposure to dengue viruses in nature. These vaccines are based on selected attenuated strains of the four dengue serotypes and employed in combination for two or three consecutive doses. In our search for a better dengue vaccine candidate, live attenuated strains were followed by non-infectious virus-like particles or the plasmids that generate these particles upon injection into the body. This heterologous prime-boost immunization induced elevated levels of virus-specific antibodies and helped to prevent dengue virus infection in a high proportion of vaccinated macaques. In macaques that remained susceptible to dengue virus, distinct mechanisms were found to account for the immunization failures, providing a better understanding of vaccine actions. Additional studies in humans in the future may help to establish whether this combination approach represents a more effective means of preventing dengue by vaccination.

Clinical Characteristics and Outcomes Among Travelers With Severe Dengue : A GeoSentinel Analysis

BACKGROUND

Dengue virus is a flavivirus transmitted by Aedes mosquitoes and is an important cause of illness worldwide. Data on the severity of travel-associated dengue illness are limited.

OBJECTIVE

To describe the epidemiology, clinical characteristics, and outcomes among international travelers with severe dengue or dengue with warning signs as defined by the 2009 World Health Organization classification (that is, complicated dengue).

DESIGN

Retrospective chart review and analysis of travelers with complicated dengue reported to GeoSentinel from January 2007 through July 2022.

SETTING

20 of 71 international GeoSentinel sites.

PATIENTS

Returning travelers with complicated dengue.

MEASUREMENTS

Routinely collected surveillance data plus chart review with abstraction of clinical information using predefined grading criteria to characterize the manifestations of complicated dengue.

RESULTS

Of 5958 patients with dengue, 95 (2%) had complicated dengue. Eighty-six (91%) patients had a supplemental questionnaire completed. Eighty-five of 86 (99%) patients had warning signs, and 27 (31%) were classified as severe. Median age was 34 years (range, 8 to 91 years); 48 (56%) were female. Patients acquired dengue most frequently in the Caribbean (n = 27 [31%]) and Southeast Asia (n = 21 [24%]). Frequent reasons for travel were tourism (46%) and visiting friends and relatives (32%). Twenty-one of 84 (25%) patients had comorbidities. Seventy-eight (91%) patients were hospitalized. One patient died of nondengue-related illnesses. Common laboratory findings and signs were thrombocytopenia (78%), elevated aminotransferase (62%), bleeding (52%), and plasma leakage (20%). Among severe cases, ophthalmologic pathology (n = 3), severe liver disease (n = 3), myocarditis (n = 2), and neurologic symptoms (n = 2) were reported. Of 44 patients with serologic data, 32 confirmed cases were classified as primary dengue (IgM+/IgG-) and 12 as secondary (IgM-/IgG+) dengue.

LIMITATIONS

Data for some variables could not be retrieved by chart review for some patients. The generalizability of our observations may be limited.

CONCLUSION

Complicated dengue is relatively rare in travelers. Clinicians should monitor patients with dengue closely for warning signs that may indicate progression to severe disease. Risk factors for developing complications of dengue in travelers need further prospective study.

PRIMARY FUNDING SOURCE

Centers for Disease Control and Prevention, International Society of Travel Medicine, Public Health Agency of Canada, and GeoSentinel Foundation.

Proceedings of the 5th Asia Dengue Summit

The 5th Asia Dengue Summit, themed "Roll Back Dengue", was held in Singapore from 13 to 15 June 2022. The summit was co-convened by Asia Dengue Voice and Action (ADVA), Global Dengue and Aedes transmitted Diseases Consortium (GDAC), Southeast Asian Ministers of Education Tropical Medicine and Public Health Network (SEAMEO TROPMED), and the Fondation Mérieux (FMx). Dengue experts from academia and research and representatives from the Ministries of Health, Regional and Global World Health Organization (WHO), and International Vaccine Institute (IVI) participated in the three-day summit. With more than 270 speakers and delegates from over 14 countries, 12 symposiums, and 3 full days, the 5th ADS highlighted the growing threat of dengue, shared innovations and strategies for successful dengue control, and emphasized the need for multi-sectoral collaboration to control dengue.

Is new dengue vaccine efficacy data a relief or cause for concern?

Dengue is a major global public health problem requiring a safe and efficacious vaccine as the foundation of a comprehensive countermeasure strategy. Despite decades of attempts, the world has a single dengue vaccine licensed in numerous countries, but restrictions and conditions of its use have deterred uptake. Recently, clinical efficacy data has been revealed for two additional dengue vaccine candidates and the data appears encouraging. In this perspective I discuss dengue, the complexities of dengue vaccine development, early development setbacks, and how the latest data from the field may be cause for measured optimism. Finally, I provide some perspectives on evaluating dengue vaccine performance and how the pursuit of the perfect dengue vaccine may prevent advancement of vaccines which are good enough.

Recent Advancements in Mosquito-Borne Flavivirus Vaccine Development

Lately, the global incidence of flavivirus infection has been increasing dramatically and presents formidable challenges for public health systems around the world. Most clinically significant flaviviruses are mosquito-borne, such as the four serotypes of dengue virus, Zika virus, West Nile virus, Japanese encephalitis virus and yellow fever virus. Until now, no effective antiflaviviral drugs are available to fight flaviviral infection; thus, a highly immunogenic vaccine would be the most effective weapon to control the diseases. In recent years, flavivirus vaccine research has made major breakthroughs with several vaccine candidates showing encouraging results in preclinical and clinical trials. This review summarizes the current advancement, safety, efficacy, advantages and disadvantages of vaccines against mosquito-borne flaviviruses posing significant threats to human health.

Dengue vaccine development: challenges and prospects

PURPOSE OF REVIEW

Dengue vaccine development is a high public health priority. To date, no dengue vaccine is in widespread use. Here we review the challenges in dengue development and the latest results for the second-generation dengue vaccines.

RECENT FINDINGS

The biggest hurdle is the immunological interaction between the four antigenically distinct dengue serotypes. The advantages of second-generation dengue vaccines are the inclusion of nonstructural proteins of the dengue backbone and a more convenient dosing with reduced numbers of doses needed.

SUMMARY

Although dengue-primed individuals can already benefit from vaccination with the first licensed dengue vaccine CYD-TDV, the public health need for the dengue-naive population has not yet been met. The urgent need remains to identify correlates of both protection and enhancement; until such correlates have been identified, all second-generation dengue vaccines still need to go through full phase 3 trials. The 5-year efficacy and safety data for both second-generation dengue vaccines are imminent.

Immunogenicity and safety of booster CYD-TDV dengue vaccine after alternative primary vaccination schedules in healthy individuals aged 9-50 years: a randomised, controlled, phase 2, non-inferiority study

BACKGROUND

Dengue is endemic in many countries throughout the tropics and subtropics, and the disease causes substantial morbidity and health-care burdens in these regions. We previously compared antibody responses after one-dose, two-dose, or three-dose primary regimens with the only approved dengue vaccine CYD-TDV (Dengvaxia; Sanofi Pasteur, Lyon, France) in individuals aged 9 years and older with previous dengue exposure. In this study, we assessed the need for a CYD-TDV booster after these primary vaccination regimens.

METHODS

In this randomised, controlled, phase 2, non-inferiority study, healthy individuals aged 9-50 years recruited from three sites in Colombia and three sites in the Philippines (excluding those with the usual contraindications to vaccinations) were randomly assigned 1:1:1 via a permuted block method with stratification by site and by age group using an independent voice response system to receive, at 6-month intervals, three doses of CYD-TDV (three-dose group), one dose of placebo followed by two doses of CYD-TDV (two-dose group), or two doses of placebo followed by one dose of CYD-TDV (one-dose group). Participants were also randomly assigned (1:1) to receive a CYD-TDV booster at 1 year or 2 years after the last primary dose. Each CYD-TDV dose was 0·5 mL and administered subcutaneously in the deltoid region of the upper arm. The investigators and sponsor, study staff interacting with the investigators, and participants and their parents or legally acceptable representatives were masked to group assignment. Neutralising antibodies were measured by 50% plaque reduction neutralisation testing, and geometric mean titres (GMTs) were calculated. Due to a change in study protocol, only participants who were dengue seropositive at baseline in the Colombian cohort received a booster vaccination. The primary outcome was to show non-inferiority of the booster dose administered at 1 year or 2 years after the two-dose and three-dose primary regimens; non-inferiority was shown if the lower limit of the two-sided adjusted 95% CI of the between-group (day 28 post-booster dose GMT from the three-dose or two-dose group vs day 28 GMT post-dose three of the three-dose primary regimen [three-dose group]) geometric mean ratio (GMR) was higher than 0·5 for each serotype. Non-inferiority of the 1-year or 2-year booster was shown if all four serotypes achieved non-inferiority. Safety was assessed among all participants who received the booster. This trial is registered with ClinicalTrials.gov, NCT02628444, and is closed to accrual.

FINDINGS

Between May 2 and Sept 16, 2016, we recruited and enrolled 1050 individuals who received either vaccine or placebo. Of the 350, 348, and 352 individuals randomly assigned to three-dose, two-dose, and one-dose groups, respectively, 108, 115, and 115 from the Colombian cohort were dengue seropositive at baseline and received a booster; 55 and 53 in the three-dose group received a booster after 1 year and 2 years, respectively, as did 59 and 56 in the two-dose group, and 62 and 53 in the one-dose group. After the three-dose primary schedule, non-inferiority was shown for serotypes 2 (GMR 0·746; 95% CI 0·550-1·010) and 3 (1·040; 0·686-1·570) but not serotypes 1 (0·567; 0·399-0·805) and 4 (0·647; 0·434-0·963) for the 1-year booster, and again for serotypes 2 (0·871; 0·673-1·130) and 3 (1·150; 0·887-1·490) but not serotypes 1 (0·688; 0·479-0·989) and 4 (0·655; 0·471-0·911) for the 2-year booster. Similarly, after the two-dose primary schedule, non-inferiority was shown for serotypes 2 (0·809; 0·505-1·300) and 3 (1·19; 0·732-1·940) but not serotypes 1 (0·627; 0·342-1·150) and 4 (0·499; 0·331-0·754) for the 1-year booster, and for serotype 3 (0·911; 0·573-1·450) but not serotypes 1 (0·889; 0·462-1·710), 2 (0·677; 0·402-1·140), and 4 (0·702; 0·447-1·100) for the 2-year booster. Thus, non-inferiority of the 1-year or 2-year booster was not shown after the three-dose or two-dose primary vaccination regimen in dengue-seropositive participants. No safety concerns occurred with the 1-year or 2-year CYD-TDV booster.

INTERPRETATION

CYD-TDV booster 1 year or 2 years after the two-dose or three-dose primary vaccination regimen does not elicit a consistent, meaningful booster effect against all dengue serotypes in participants who are seropositive for dengue at baseline.

FUNDING

Sanofi Pasteur.

TRANSLATION

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

Clinical Safety Experience of TAK-003 for Dengue Fever: A New Tetravalent Live Attenuated Vaccine Candidate

BACKGROUND

An unmet medical need remains for an effective dengue tetravalent vaccine that can be administered irrespective of previous dengue exposure. TAK-003, a dengue tetravalent vaccine, has demonstrated efficacy in an ongoing phase 3 trial in children and adolescents living in dengue-endemic areas, with an acceptable safety profile in both dengue-naive and dengue-exposed individuals.

METHODS

Safety findings are presented herein from an integrated analysis of data for healthy 4-60-year-olds from two phase 2 and three phase 3 double-blind, placebo-controlled clinical trials of TAK-003 (TAK-003, n = 14 627; placebo, n = 7167). Safety evaluation included analyses of postinjection reactogenicity, unsolicited adverse events (AEs), serious AEs (SAEs), and deaths. Subgroup analyses were performed by age group, baseline serostatus, and gender.

RESULTS

The most common local and systemic AEs were injection site pain (43% for TAK-003 and 26% for placebo) and headache (34% and 30%, respectively). Injection site AEs were mostly mild and resolved within 1-3 days. Unsolicited AEs and AEs leading to discontinuation occurred with similar frequency across both groups, while SAEs were fewer for TAK-003 recipients (6% vs 8% for placebo). Four of the 5 vaccine-related SAEs (which included hypersensitivity, dengue fever, and dengue hemorrhagic fever) occurred in the placebo group. No deaths were considered vaccine-related. Subgroup analyses showed no differences in safety by baseline serostatus or by gender, albeit analysis by age indicated greater local reactogenicity rates for adolescents (46% for TAK-003 and 28% for placebo) and adults (56% and 19%, respectively) than for children (37% and 25%, respectively).

CONCLUSIONS

No important safety risks were identified, and TAK-003 was well tolerated irrespective of age, gender, or baseline dengue serostatus in recipients aged 4-60 years.

A case-control study to determine the effectiveness of a tetravalent dengue vaccine in the state of Paraná, Brazil

Background

The Brazilian state of Paraná conducted a mass vaccination campaign against dengue with the tetravalent attenuated vaccine CYD-TDV. The campaign targeted thirty endemic municipalities. The objective of this study was to assess the effectiveness of CYD-TDV in preventing symptomatic virologically confirmed dengue cases according to specific age groups in five of the municipalities.

Methods

A case-control study was carried out in the five most populous municipalities targeted by the vaccination, with a vaccine uptake of 25%. Symptomatic dengue cases were identified by the municipal health departments. The age groups targeted were 15-18 and 19-27 in four municipalities and 9-14 and 28-44 in one municipality. All cases were confirmed by real time reverse transcription quantitative polymerase chain reaction (RT-qPCR). For each case, two controls were selected: a neighbourhood control and a workplace or school/college control, matched by age group. A conditional logistic regression model was used to determine the odds ratio for vaccination and the vaccine effectiveness.

Findings

Study participants included 618 RT-qPCR-confirmed dengue cases and 1,236 matched controls (with a non-reactive dengue IgM serologic test). Vaccine effectiveness against dengue due to any serotype was 11·1% (95% CI: -19·0%; 33·6%). Effectiveness against DENV-1 was 33·3% (95% CI: -5·0%; 57·6%) and against DENV-2 was -56·7% (95% CI: -142·2%; -5·0%). No DENV-3 was detected. The vaccine was significantly effective in the prevention of DENV-4 cases (VE = 93·3%; 95% CI: 47·7%; 99·2%).

Interpretation

CYD-TDV was effective in the prevention of symptomatic cases due to DENV-4, but not due to any serotype. The low dengue seroprevalence in the target population could possibly be related to these results.

Funding

This study was supported through a grant to the Sabin Vaccine Institute from Sanofi-Pasteur. Sanofi-Pasteur had no role in the study design, protocol development, data collection, analysis, or publication of results.