The dengue outbreak that has unfolded in Latin America over the past three months is staggering in its scale – a million cases in Brazil in a matter of weeks, a huge spike in Argentina, a state of emergency declared in Peru, and now another, in Puerto Rico.
He warns of a changing landscape for the disease. The mosquitoes that spread dengue thrive in densely populated cities with weak infrastructure and in warmer, wetter environments — the type of habitat that is expanding rapidly with climate change.
More than 3.5 million dengue cases have been confirmed by governments in Latin America in the first three months of 2024, up from 4.5 million in all of 2023. There have been more than 1,000 deaths so far this year. The Pan American Health Organization is warning that this could be the worst dengue year on record.
The rapidly changing disease landscape needs new solutions, and researchers in Brazil provided the only piece of good news in this story with the recent announcement that a clinical trial of a new dengue vaccine, given with a single shot, provided strong protection against disease .
There are two existing dengue vaccines, but one is an expensive two-shot regimen, while the other can only be given to people who already have a dengue infection.
The new one-dose vaccine uses live, weakened forms of all four strains of the dengue virus and was created by scientists at the United States’ National Institutes of Health. The vaccine was licensed for development by the Instituto Butantan, a huge public research institute in Sao Paulo, and Merck & Co.
The vaccine will butadane. It already produces most of the vaccines used in Brazil and has the capacity to produce tens of millions of doses of this new one. The institute plans to submit the dengue vaccine to Brazil’s regulatory agency for approval in the coming months and could begin production next year.
But that won’t help with this outbreak, and until production begins and a national facility begins, it may not be enough to help with the next one. Dengue usually erupts in cycles of three or four years.
And it won’t necessarily help the rest of Latin America: Butantan will only make the vaccine for Brazil. Other countries in the region battling dengue fever will have to buy it from Merck, which has not said what it plans to charge for the shot.
And there is, of course, demand for a dengue vaccine beyond America: mosquitoes are spreading the disease in Croatia, Italy, California and other areas that have never seen it before. Places that used to deal with mild outbreaks now face record highs: Bangladesh had 300,000 cases last year.
Dengue fever is commonly known as relapsing fever, after the excruciating joint pain it causes. Not everyone experiences this pain: Three-quarters of people infected with dengue fever have no symptoms at all, and among those who do, most cases are only mild flu-like.
But about 5 percent of people who get sick will develop what’s called severe dengue fever. Plasma, the protein-rich fluid component of blood, can begin to leak from blood vessels, sending patients into shock or organ failure.
When patients with severe dengue fever are treated with blood transfusions and intravenous fluids, the mortality rate tends to be between 2 and 5 percent. But when they don’t get treatment — because they don’t realize it’s dengue and don’t seek treatment quickly enough, or because health centers are overwhelmed — the death rate is 15 percent.
In Brazil, the current dengue epidemic is hitting children the hardest. Those under 5 have the highest death rate of any age group, followed by those aged 5 to 9. Adolescents between 10 and 14 have the highest number of confirmed cases, according to the Instituto Oswaldo Cruz, a national public health research center.
As clinics began to be overwhelmed by dengue patients in January, the Brazilian government bought the entire world’s stock of a Japanese dengue vaccine called Qdenga. Public health nurses deliver it to children ages 6 to 16, but there will be enough vaccine to fully vaccinate 3.3 million of Brazil’s 220 million people this year.
This major national effort will protect a few million children, but will do nothing to herd immunity.
Qdenga isn’t cheap: it’s about $115 per dose in Europe and $40 in Indonesia. Brazil pays $19 per tranche, having negotiated a lower price for its huge market.
Takeda Pharmaceuticals, which makes Qdenga, announced a deal last month with Biological E, a major Indian generic drugmaker, to license and produce up to 50 million doses a year, part of a drive to speed up production. The Indian vaccine should cost much less. But Biological E is unlikely to get regulatory approval to bring it to market before 2030. It’s a slow process that involves transferring technology, building a production line, and getting a new version of even a known product approved by the regulatory authorities.
Dengue costs Brazil at least $1 billion a year in health care treatment and lost productivity. And that number doesn’t take into account the human suffering involved.
There are four different strains of the dengue virus, further complicating the process of making a vaccine: The potentially fatal form of the disease is more common when a person has a second infection, with a different strain than the one they had the first time. Qdenga protects against all four strains of dengue, and it is hoped that the new Butantan vaccine does as well, although the data released so far show that it was only tested against the two types circulating during the first part of the trial. more results are expected in June.
Millions more people will have been exposed to dengue when this outbreak finally passes. But they will need this new vaccine more urgently than ever.
