whether or not they previously have been exposed to the virus, said Xavier Sáez-Llorens, MD, of Hospital del Niño Dr José Renán Esquivel, Panama City, Republic of Panama, and his associates.
Studies show dengue to be the most common mosquito-borne viral disease affecting humans, occurring in 125 countries and causing approximately 100 million symptomatic infections annually. Vector control has not halted the global spread of dengue, necessitating development of vaccines. A vaccine for people aged 9 years and older has been licensed, but there remains the need for a safe and effective vaccine against all four dengue virus serotypes for all ages, said Dr. Sáez-Llorens and his associates.
Takeda’s live tetravalent dengue vaccine, TDV, has an “attenuated [dengue virus serotype] DENV-2 virus strain (TDV-2) and three chimeric (dengue–dengue) viruses containing the premembrane and envelope protein genes of DENV-1, DENV-3, and DENV-4 genetically engineered into the attenuated TDV-2 genome backbone (TDV-1, TDV-3, and TDV-4),” the investigators explained.
In an ongoing, randomized, double-blind, placebo-controlled study in dengue-endemic Panama, the Dominican Republic, and the Philippines, healthy children aged 2-17 years were randomly assigned to receive either one TDV dose at 0 months and one dose at 3 months (group 1); one dose at 0 months (group 2); one dose at 0 months and a booster at 12 months (group 3); or a placebo (group 4). At 6 months, 68% of children were seropositive for all four serotypes after one dose, and 85% were seropositive for all four serotypes after two doses; this occurred regardless of whether the children had previously been exposed to dengue. Group 3 has not yet received its 3-month booster.
The vaccine was well tolerated and safe. In children younger than 6 years, fever and irritability were the only systemic adverse events reported more often with the vaccine than with placebo. In children older than 6 years, only headache and myalgia were more common with the vaccine than with placebo, Dr. Sáez-Llorens and his associates noted.
“These data support phase III evaluation of the efficacy and safety of TDV given in a two-dose schedule 3 months apart, with analyses that take into account baseline age and dengue serostatus,” they concluded.
Read more in The Lancet Infectious Diseases (