Brazil suspends Butantan dengue vaccine amid severe adverse events

The Brazilian Ministry of Health temporarily halted the use of the Butantan-DV dengue vaccine after 42 serious adverse events were reported, including two deaths, among more than 500,000 administered doses. Minister Alexandre Padilha emphasized the precautionary nature of the decision and noted that the reactions, such as abdominal pain, persistent vomiting and bleeding, were not observed in earlier clinical trials. The vaccine, approved by Anvisa in November 2025 for people aged 12 to 59, had been rolled out to primary‑care health workers nationwide.

Despite the suspension, the Instituto Butantan continues a phase‑III study of the vaccine in older adults. The trial, which began recruiting volunteers aged 60‑79 in January 2026, involves 997 participants across four centres in Rio Grande do Sul and Paraná. Director Esper Kallás said the study aims to assess safety and immune response in the elderly, adding, "We are putting the pieces of the puzzle together to understand if the warning signals of the 42 cases relate to other studies." The investigation into the adverse events will remain ongoing while the elderly trial proceeds under close monitoring.