Brazilian dengue vaccine shows promise in phase 3 trial, preventing 80% of cases

A single-dose dengue vaccine produced by Butantan Institute in São Paulo state (Brazil) prevents development of the disease in 79.6% of those vaccinated, according to an article published in The New England Journal of Medicine.

Called Butantan-DV, the vaccine contains attenuated versions of all four dengue virus serotypes. The results of the ongoing Phase 3 trial show that it is safe and effective for all age groups between 2 and 59, and for people with or without a prior history of infection by dengue virus.

“Publication of the article in the world’s leading medical journal attests to the rigor and quality of the work done by researchers at 16 Brazilian centers located in all five regions of the country, and coordinated by Butantan Institute,” infectious disease specialist Esper Kallás, first author of the article, told Agência FAPESP. “In June, we’ll complete the five-year follow-up period. Once the data has been consolidated, we’ll know how long the protection induced by the vaccine will last.”

Also according to Kallás, who heads Butantan Institute, the researchers plan to submit a report to ANVISA, Brazil’s health surveillance agency, in the second half of this year in order to apply for registration of the vaccine.

“If all goes well, we’ll win definitive approval for the vaccine in 2025. We already have the infrastructure to produce it at Butantan Institute, although it can still be perfected. After all, it’s tetravalent, corresponding to four vaccines in one,” he said.

The article published today describes the results of the first two years of the Phase 3 clinical trial, which began in February 2016 and involves 16,235 participants in 13 states. Preliminary data disclosed by Butantan Institute in December 2022 pointed to overall efficacy of 79.6%. The results for each subgroup evaluated have now been detailed.

Vaccine efficacy was 80.1% for participants aged 2-6, 77.8% for those aged 7-17, and 90.0% for 18-59 age group. Stratification by serological status showed protection for 73.6% of participants with no evidence of prior infection by dengue virus and 89.2% of those previously exposed to the virus. Efficacy was 89.5% against dengue serotype 1 (DENV-1) and 69.6% against serotype 2 (DENV-2).

It was not possible to assess the vaccine’s efficacy against serotypes 3 and 4 because they were not circulating during the follow-up period. Most adverse side effects were classified as mild or moderate. The main reactions were pain and redness at the injection site, headache, and fatigue. Severe adverse events relating to the vaccine were recorded for under 0.1% of all those vaccinated, and all of them recovered.

“Findings from Phase 2 [the previous clinical trial] showed that the four attenuated viral serotypes in Butantan-DV multiply in the human organism and induce a balanced response in terms of antibody production. This leads us to conclude that its efficacy against DENV-3 and DENV-4 will also be good,” said virologist Maurício Lacerda Nogueira, one of the coordinators of the trials.

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