The Brazilian government announced on Monday the temporary suspension of the world's first single-dose dengue vaccine, after the identification of two suspected deaths related to the immunization.
Since the beginning of the year, more than 500,000 people, mainly health professionals, have received the vaccine developed by the Butantan Institute and approved in November by Brazilian health authorities. Between January and May, approximately 3,700 people presented symptoms similar to those of dengue, representing 0.7% of the total vaccinated. In addition, 42 individuals had more severe reactions.
Three serious cases were recorded, including the death of a 58-year-old man and a 48-year-old woman. Another woman, 38 years old, had to be admitted to an intensive care unit but has already been discharged. Health Minister Alexandre Padilha stated that there is not enough data to establish a causal relationship between the vaccine and these cases, but that they represent a warning sign.
Padilha emphasized that the adverse effects were completely unexpected, as they were not observed during clinical trials with more than 16,000 volunteers, in which the vaccine showed 91.6% efficacy against the most severe forms of the disease. Although serious cases represent only 8 per 100,000 vaccinated individuals, the decision for a temporary suspension was made as a precaution.
Dengue, transmitted by the Aedes aegypti mosquito, can cause high fever, headaches, muscle pain, nausea, and skin rashes, and in exceptional cases can be fatal. In 2024, Brazil recorded more than 6,000 deaths from the disease, nearly half the global total, although the number dropped to around 1,800 last year. Paraguay, like other countries in the region, also faces recurrent dengue outbreaks, making vaccine development and safety a matter of regional interest.
To date, the only other dengue vaccine available globally is TAK-003, which requires two doses administered three months apart, in accordance with World Health Organization (WHO) guidelines. The single-dose vaccine could facilitate and accelerate mass immunization campaigns.