Brazil has suspended a vaccination campaign after two people died.
The campaign for the dengue vaccine—the world’s first single-dose vaccine—has been halted as authorities investigate deaths and other cases with “warning signs” such as persistent vomiting, Brazil’s Ministry of Health said in a June 8 statement.
The 42 cases represent 0.008 percent of the 500,000 doses of the vaccine administered through May 30, according to the ministry, and officials say they aren’t sure the vaccine caused any of the problems.
“This discontinuation has a purpose,” Health Minister Alexandre Padilha said in a statement.
“First, it is a precautionary measure that should always guide those who respect life and those who respect science, even more so when we are talking about vaccination. Second, it allows the Ministry of Health, Anvisa (Brazilian Health Regulatory Agency), and the Butantan Institute to deepen the investigation of the cases, especially the registered deaths, for which there is still not enough information to establish a causal relationship with the vaccine.”
The suspension “aims to ensure the safety of the population in the next stages of vaccination,” the Butantan Institute, an agency that works closely with the São Paulo State Health Department, said in a statement.
The institute said that if the vaccine’s safety is confirmed, “vaccination can resume soon.” It had planned to expand the campaign to older individuals, pending the results of testing in that population.
Dengue is a viral infection transmitted to humans by mosquitoes. In 2024, Brazil registered 6.5 million probable cases of dengue fever—four times as many as in 2023, according to the Ministry of Health.
By mid-November 2025, 1.6 million probable cases had been reported. Since the beginning of the 2000s, more than 20 million Brazilians have been affected by the disease.
The institute developed the vaccine using technology created by U.S. researchers. It is a live attenuated vaccine containing weakened strains of four dengue virus serotypes.
Brazilian officials approved the vaccine in 2025.
Officials launched the campaign in early 2026 to prevent dengue cases.
Testing had indicated the vaccine provided protection against dengue and severe dengue.
The campaign targeted health care workers and people aged 15 to 49 in three cities in Araguaína, an area in Brazil’s northern Tocantins state.
Fewer Dengue cases have been recorded in Brazil since the vaccine was rolled out, compared to the same time period in 2024, according to health officials.
