Safety and immunogenicity of a tetravalent dengue vaccine in children aged 2-17 years: a randomised, placebo-controlled, phase 2 trial.

BACKGROUND: An unmet clinical need remains for an effective tetravalent dengue vaccine suitable for all age groups, regardless of serostatus. We assessed the immunogenicity and safety of three different dose schedules of a tetravalent dengue vaccine (TAK-003) over a 48-month period in children living in dengue-endemic countries. METHODS: We did a large, phase 2, double-blind, placebo-controlled trial at three sites in the Dominican Republic, Panama, and the Philippines. Healthy participants aged 2-17 years were randomly assigned 1:2:5:1 using an interactive web response system with stratification by age to receive either a two-dose primary series (days 1 and 91), one primary dose (day 1), one primary dose plus booster (days 1 and 365), or placebo. Participants and relevant study personnel were masked to the random assignment until completion of the study at month 48. To maintain masking, TAK-003 recipients were administered placebo doses when appropriate. The primary objective was assessment of neutralising geometric mean titres for each serotype to month 48 assessed in the per-protocol immunogenicity subset. Secondary safety endpoints included proportions of participants with serious adverse events and symptomatic virologically confirmed dengue. This study is registered with ClinicalTrials.gov, NCT02302066. FINDINGS: Between Dec 5, 2014, and Feb 13, 2015, 1800 children were randomly assigned to the following groups: two-dose primary series (n=201), one primary dose (n=398), one primary dose plus 1-year booster (n=1002), and placebo (n=199). Of them, 1479 (82%) participants completed the 48-month study. Immunogenicity endpoints were assessed in 562 participants enrolled in the immunogenicity subset, of whom 509 were included in the per-protocol subset. At month 48, antibody titres remained elevated in all TAK-003 groups compared with placebo, irrespective of baseline serostatus. At month 48, geometric mean titres were 378 (95% CI 226-632) in two-dose, 421 (285-622) in one-dose, 719 (538-960) in one-dose plus 1-year booster, and 100 (50-201) in placebo recipients against DENV 1; 1052 (732-1511), 1319 (970-1794), 1200 (927-1553), and 208 (99-437) against DENV 2; 183 (113-298), 201 (135-298), 288 (211-392), and 71 (37-139) against DENV 3; and 152 (97-239), 164 (114-236), 219 (165-290), and 46 (26-82) against DENV 4; and tetravalent seropositivity rate was 89% (79-96), 86% (80-92), 97% (93-99), and 60% (47-72), respectively. Virologically confirmed dengue was recorded in 37 (2%) TAK-003 and 13 (7%) placebo participants, with a relative risk of 0·35 (0·19-0·65). No vaccine-related serious adverse events or severe dengue virus disease were reported. INTERPRETATION: TAK-003 elicited antibody responses against all four serotypes, which persisted to 48 months post-vaccination, regardless of baseline serostatus. No important safety risks were identified. We observed a long-term reduction in risk of symptomatic dengue virus disease in vaccinees. Results from this study provide a long-term safety database and support assessment of the vaccine in the ongoing phase 3 efficacy study. FUNDING: Takeda Vaccines.

Immunogenicity and safety of one versus two doses of tetravalent dengue vaccine in healthy children aged 2-17 years in Asia and Latin America: 18-month interim data from a phase 2, randomised, placebo-controlled study.

BACKGROUND: Development of vaccines that are effective against all four dengue virus serotypes (DENV-1-4) in all age groups is important. Here, we present 18-month interim data from an ongoing study undertaken to assess the immunogenicity and safety of Takeda's tetravalent dengue vaccine (TDV) candidate over 48 months in children living in dengue-endemic countries. METHODS: We undertook a phase 2, multicentre, randomised, double-blind, placebo-controlled study at three sites in the Dominican Republic, Panama, and the Philippines. We randomly assigned children aged 2-17 years to receive either two TDV doses 3 months apart (group 1), one TDV dose (group 2), one TDV dose and a booster dose 1 year later (group 3), or placebo (group 4). We did the randomisation (1:2:5:1) using an interactive web response system stratified by age. The primary endpoint of this 18-month interim analysis was DENV serotype-specific antibody geometric mean titres (GMTs) in the per-protocol immunogenicity subset on days 1, 28, 91, 180, 365, 393, and 540. Secondary safety endpoints were the proportions of participants with serious adverse events and with virologically confirmed dengue in the safety set, and solicited and unsolicited adverse events in the immunogenicity subset. This trial is registered with ClinicalTrials.gov, number NCT02302066. FINDINGS: Between Dec 5, 2014, and Feb 13, 2015, 1800 children were randomly assigned to group 1 (n=201), group 2 (n=398), group 3 (n=1002), and group 4 (n=199). 1794 participants received at least one dose of TDV or placebo (safety set), of whom 562 participated in the immunogenicity subset and 509 were included in the per-protocol set. Antibody titres remained elevated 18 months after vaccination in all TDV groups. At day 540, in groups 1, 2, 3, and 4, respectively, DENV-1 GMTs were 476 (95% CI 286-791), 461 (329-647), 1056 (804-1388), and 92 (49-173); DENV-2 GMTs were 1212 (842-1744), 1242 (947-1628), 1457 (1182-1796), and 177 (93-337); DENV-3 GMTs were 286 (171-478), 298 (205-433), 548 (411-730), and 78 (44-137); and DENV-4 GMTs were 98 (65-150), 102 (75-139), 172 (133-222), and 33 (21-52). Limited differences in GMTs were observed between groups 1 and 2 (in which participants received one and two doses of TDV, respectively). In baseline-seronegative participants, a 1-year booster clearly increased GMTs. Vaccine-related unsolicited adverse events occurred in 14 (2%) of 562 participants, but no vaccine-related serious adverse events arose. Symptomatic, virologically confirmed dengue was recorded in 21 (1·3%) of 1596 participants vaccinated with TDV compared with nine (4·5%) of 198 placebo recipients. INTERPRETATION: TDV was well tolerated and immunogenic against all four dengue serotypes, irrespective of baseline dengue serostatus. These data provide proof of concept for TDV and support the ongoing phase 3 efficacy assessment of two doses 3 months apart. FUNDING: Takeda Vaccines.