Brazil prepares to test bird flu vaccine in people
Butantan Institute, linked to the São Paulo State Health Secretariat, will begin human trials of the first Brazilian vaccine against bird flu (H5N8). The institute was authorized by Brazil’s drug watchdog Anvisa last Tuesday (Jul. 1) to begin clinical trials and is now awaiting approval from the National Research Ethics Commission.
The monovalent influenza A (H5N8) inoculation should first be tested in two doses, 21 days apart, on adults aged 18 to 59. Tests will then be carried out on people over 60.
The institute has completed pre-clinical studies on mice and rabbits with positive results for safety and immunogenicity (the ability to generate an immune response). Butantan intends to recruit 700 adult and elderly volunteers to take part in phases one and two of the study at five research centers in the states of Pernambuco, Minas Gerais, and São Paulo.
The follow-up for these participants should end in 2026, so that data covering a wide age range can be submitted to Anvisa.
Risk of a new pandemic
Butantan Institute Director Esper Kallás noted there is a large number of bird influenza viruses, adding that a small percentage of them can become aggressive and cause more serious illnesses. Even though they primarily affect birds, these viruses can reach some mammals that come into contact with them, and finally, if they adapt, they may cause infections in humans. Since 1996, he said, a type of bird-specific virus called H5 has proved capable of being transmitted sporadically to humans.
“In recent years, the virus has been adapting more and more and causing waves of deaths in mammals—first in aquatic mammals, but now also in terrestrial mammals. It’s getting closer and closer to having the adaptations needed to be transmitted to people. This alerts the entire scientific and public health care community to the possibility of a pandemic caused by bird flu,” he argued.
Lethality
According to Anvisa, experts around the world are warning of the risk of the spread of new variants of the bird flu virus, including—H5N1, H5N8, and H7N9—which are drawing attention due to their high lethality potential and ability to mutate. Since 2021, they have caused the deaths of 300 million birds and impacted 315 wild species across 79 countries, as per global data.
“In human beings, though still rare, the cases stand out for their seriousness. From 2003 to 2024, 954 people were infected in 24 countries, with 464 deaths—a fatality rate of 48.6 percent, significantly higher than the rate recorded during the COVID-19 pandemic, of less than one percent,” the regulatory agency pointed out.
