There’s now a vaccine approved to treat dengue, a disease that affects tens of millions across the globe

Thomson Reuters

The first vaccine to treat dengue — a viral disease which affects tens of millions worldwide — just got approved in a country heavily affected by the disease.

Sanofi's vaccine for dengue will make its market debut in Mexico, the French drugmaker said on Wednesday.

The company also expects to file for more approvals in about 20 countries by the end of the year.

Dengue is a mosquito-borne disease that causes flu-like symptoms which can later develop into a more serious and deadly infection called severe dengue or Dengue Haemorrhagic Fever. There are four types of the virus, or "serotypes," that cause dengue. Contracting one type of the virus gives you immunity over that specific type for life, but immunity to the three other types is only partial and temporary.

Overall, the disease is seen as a threat to about half of the world's population. Some 400 million people are believed to be infected annually. Dengue is typically found in tropical and sub-tropical climates, and Mexico is one of many affected countries in the Americas, according to the WHO. Large outbreaks of dengue have been reported there in recent years, the CDC reports.

Sanofi Pasteur, the group's vaccines division, said Mexico had approved the preventive treatment, called Dengvaxia, for all four dengue virus serotypes, but only for patients aged 9 to 45 who live in areas where the disease is endemic.

This means the world's first dengue vaccine has no approval yet for use on young children, a population considered to be most at risk, or for use by tourists.

Guillaume Leroy, who leads the dengue team at Sanofi Pasteur, said the vaccine acted best as an immune booster for patients with some previous exposure.

He told Reuters in an interview that additional data over the coming years would be needed to assess whether the vaccine may be of use to travelers.

"Health authorities will have to determine (future) recommendations," he said, adding Sanofi's first 20 market approval requests were all in South America and Asia. Europe is the target for early next year and the United States in early 2017, he said.

"Mexico is one of the countries where we started our clinical trials, which has been associated with the program from the very beginning and whose regulatory authority is certified by the WHO," said Olivier Charmeil, Sanofi's executive vice president, vaccines.

Charmeil said Mexican regulators had given their green light based on results from a clinical development program involving over 40,000 people from 15 countries of different ages, geographic and epidemiological settings as well as of varied ethnic and socio-economic backgrounds.

Leroy said the vaccine reduced the risk of hospitalization by 80% and lowered the possibility of developing the severest, hemorrhagic form of the disease by 93%.

Previous results showed the vaccine had recorded low protection levels against the serotype 2 form and shown poor performance with young children.

The WHO has a target in some 128 countries to reduce dengue mortality by 50% and infections by 25% by 2020, using 2010 as the baseline.

"What we want to do is to achieve this (WHO) goal. Results show that if you vaccinate 20 percent of the population in 10 endemic countries that have taken part in our phase III studies you can potentially reduce the dengue burden by 50 percent over a five-year period," Leroy said.

He and Charmeil declined to give figures on output and sales outlook but confirmed full scale production was ramping up toward 100 million doses annually and said Dengvaxia should be one of the top three Sanofi Pasteur products in the next five years.

Sales at Sanofi Pasteur were up 7.2% at constant exchange rates in 2014 at 3.97 billion euros ($4.36 billion). Analysts said last year the vaccines may generate 1 billion euros in sales every year although pricing remains unclear.

Other drugmakers including Japan's Takeda and US Merck are also working on dengue vaccines but are several years behind.

Sanofi's vaccine will start being shipped to Mexico starting early next year.