The dengue vaccine under development by the Butantan Institute (i.e. Butantan-DV) shows 79.6% overall efficacy to prevent the disease, according to initial results from the phase 3 clinical study. There were no cases of severe dengue fever or with alarm signs during the two-year follow-up of the volunteers.
The results refer to analyses conducted between February 2016 and July 2021, by 16 research centers in different regions of Brazil, including 16,235 volunteers aged 2 to 59 years, who received a single dose of the vaccine. The incidence of laboratory-confirmed symptomatic dengue cases was observed after 28 days of vaccination until the second year of follow-up of individuals. The study will continue until all participants complete five years of follow-up in 2024.
People with and without previous exposure to dengue virus were included in the research. In participants who had already been infected before the study, the efficacy was 89.2%. In those who had never contracted the disease, protection was 73.5%.
The vaccine is tetravalent (capable of protecting against the four serotypes of the virus) and the study evaluated the efficacy against the serotypes DENV-1 and DENV-2, which was 89.5% and 69.6%, respectively.
There are no efficacy data against DENV-3 and DENV-4 since these viruses did not circulate widely in the country during the analyzed period. However, phase 3 is ongoing and there are clinical development plans to generate efficacy data for these two serotypes. Previously, in phase 2, published on The Lancet Infectious Diseases, 80% of the volunteers produced antibodies against all four types.
Butantan-DV, analogous to the American vaccine TV003, is developed in partnership with the multinational pharmaceutical company MSD and with support from the U.S. National Institutes of Health (NIH). The new data reinforce the vaccine's high ability to generate immune response against dengue, already observed in earlier phases of the study.
Of the 16,235 volunteers who participated in the study, 10,259 received the vaccine. By 21 days after vaccination, only three (less than 0.1%) had serious adverse events related to the immunization.
Adverse reactions were comparable between the placebo and vaccine groups, except for expected off-site reactions, such as fever and skin irritation.
The frequency of adverse events was similar among the three age groups (2-6, 7-17 and 18-59 years) and among participants previously exposed to dengue or not.
"This data represents an important milestone for the Brazilian scientific community in the