Brazil suspends the world's first vaccine against dengue fever after two deaths under investigation

Since the beginning of the year, Brazil has vaccinated over 500,000 people, mostly members of the medical staff, with a vaccine developed by the Butantan Institute. This vaccine, approved in November, targets dengue fever, a serious disease transmitted by the tiger mosquito.

However, the Ministry of Health reported 3,703 cases of symptoms similar to dengue fever and 42 more severe reactions, including two deaths. Health Minister Alexandre Padilha stated that there is not enough evidence to establish a link between the vaccine and these cases, but he decided to temporarily suspend vaccination as a precaution.

Authorities emphasized that these adverse effects were unexpected, considering the 91.6% efficacy observed in previous trials. In 2024, Brazil reported over 6,000 deaths due to dengue fever, but the situation significantly improved in 2025.