Brazil rolls out dengue vaccines as cases rise sharply

Brazil is scrambling to roll out new vaccines against dengue fever after the number of cases of the mosquito-borne disease more than quadrupled from last year’s rates.

The sharp increase, which has prompted several states to declare health emergencies and the Rio de Janeiro government to declare an epidemic, came after health officials warned of a rise in cases due to warmer weather from climate change and the El Niño weather pattern.

The country has reported more than 700,000 cases so far this year, up sharply from the 165,000 cases in the same period of 2023. More than 100 deaths have been reported from the virus, which is transmitted by mosquitoes and can cause high fever, muscle pain and internal bleeding.

The health ministry warned earlier this year that the number of dengue cases could reach a record 5mn in 2024, a more than threefold increase from the 1.65mn cases recorded last year, which resulted in 1,094 deaths. The previous record was 1.68mn cases in 2015.

The number of dengue cases typically peaks in April before tapering off, although health officials have said that rising global temperatures will allow the mosquitoes that carry the virus to thrive for longer. Last year Brazil reported its hottest year on record.

Argentina and Paraguay have also reported a surge in dengue cases. The Argentine ministry of health this week said 48,000 cases had been recorded between late July 2023 and mid-February, compared with just 1,000 in the same period a year earlier.

Nísia Trindade, Brazil’s health minister, said: “Now is the time for all of Brazil to unite against dengue. This is the time to intensify care and prevention . . . After 40 years of dealing with dengue epidemics, we now have an important scientific achievement: a vaccine.”

This month Brazil started distributing a vaccine produced by Japanese pharmaceutical group Takeda. Known as Qdenga, the vaccine has an efficacy rate of 80.2 per cent and consists of two shots with a three-month interval between them.

Because of supply bottlenecks, the vaccine is primarily being administered to children between the age of 10 and 14, who are the group most often hospitalised with the virus after elderly people. Regulators have not yet approved the vaccine for senior citizens.

Trindade said Brazil was the first country to incorporate a dengue vaccine into its free public health system. The São Paulo-based Butantan Institute has also developed a vaccine, but it has yet to be approved by regulators.

The disease is transmitted by the Aedes aegypti mosquito, which thrives in pools of stagnant water.

“The poorest regions suffer the most because of the housing conditions and urban structure that support the spread of mosquitoes. Mortality is higher among the poorest,” said Alberto Chebabo, president of the Brazilian Society of Infectious Diseases.

“We’re now in the rainy and hot season, so we can’t reverse the proliferation of the mosquito. The focus now is on care to reduce mortality.”

The World Health Organization has described dengue fever as a “substantial public health challenge”, noting a “10-fold surge in reported cases worldwide increasing from 500,000 to 5.2mn” between 2000 and 2019.

Additional reporting by Ciara Nugent and Beatriz Langella