Dengue Vaccine Shows Promise Against 3 Out of 4 Viruses

The most advanced experimental vaccine against dengue protected some children against the disease in a study, though a more effective weapon may still be needed to curb the most widespread mosquito-borne infection.

In a clinical trial involving more than 10,000 children in Southeast Asia, the vaccine reduced the risk of infection by 56.5 percent, and the chance of severe complications by 88.5 percent, according to findings published today in The Lancet medical journal. The inoculation was less effective among the youngest children who are most in danger of contracting dengue, and failed to protect against one of four viruses that cause it.

Sanofi, the Paris-based developer of the vaccine, said it expects results from a larger trial in Latin America by the end of the year. The drugmaker plans to seek approval for the vaccine next year in the countries most affected by dengue. The shot may garner 950 million euros ($1.3 billion) in sales by 2018, according to Mark Clark, an analyst at Deutsche Bank AG in London.

For the moment, Sanofi’s vaccine “is the best we have,” Annelies Wilder-Smith, a professor of infectious diseases at Nanyang Technological University in Singapore, wrote in a commentary accompanying the study. “However, with a 56 percent efficacy, this vaccine will never be a single solution.”

Sanofi shares rose 0.4 percent to 76.03 euros as of 10:19 a.m. in Paris.

Dengue, for which there is no approved vaccine or treatment, causes flu-like illness that can develop into potentially fatal complications including bleeding gums, vomiting, rapid breathing and severe abdominal pain.

Key West

The disease isn’t confined to poor and developing countries. Cases have been reported in Texas and Florida, where an outbreak in Key West sickened at least 66 people in 2010. An outbreak on the Portuguese resort island of Madeira in 2012 sickened more than 2,000 people, including tourists. Two locally acquired cases were reported in Nice, France, in 2010.

Dengue is caused by four related viruses spread by mosquitoes. About half the world’s population lives in countries threatened by dengue, the World Health Organization estimates. There are about 390 million infections a year, with about 96 million people getting sick to some degree, according to research published last year.

Vaccine Pricing

Sanofi has spent about 1.3 billion euros developing the vaccine, according to Clark. That includes 300 million euros to build a factory to make the vaccine in Neuville-sur-Saone, near Lyon in France, that will be capable of churning out about 100 million doses a year, said Guillaume Leroy, the head of the company’s dengue program, on a conference call. The vaccine requires three doses, each six months apart.

Leroy said it’s too early to talk about the price Sanofi will charge for the vaccine. The company may sell the three-dose course for about $30 in developing nations and about $150 for travelers from rich countries, Deutsche Bank’s Clark estimates.

Sanofi said in April that the vaccine reduced infections by 56 percent in the company-funded trial, without giving any other details. The results announced today showed the vaccine provided 50 percent protection against type 1 of the virus, 78 percent against type 3 and 75 percent against type 4, but only 35 percent against type 2, a result that wasn’t statistically significant.

Different Types

The weakness of the vaccine against type 2 confirms the result of an earlier trial in Thailand, in which the overall risk reduction was 33 percent because type 2 was the main strain circulating when the research was done. The higher efficacy in today’s study may be because type 2 was less common during the late-stage trial, the researchers said.

“It’s still not an optimal vaccine,” said Scott Halstead, a senior adviser to the Dengue Vaccine Initiative, a group of four organizations that encourages the development of vaccines. “We’re all accustomed to efficacy rates of 95 percent, which is what you get when you have the measles, mumps and rubella vaccine.”

The vaccine was more effective in people who had been exposed to dengue previously than those who had never been exposed, suggesting it may be “of limited use in countries with low dengue endemicity, or in international travelers from non-dengue-endemic countries,” Wilder-Smith said.

There were 541 cases of dengue reported in the U.K. last year among people returning from dengue-affected countries, a 58 percent increase over 2012, Public Health England said this week.

The frequency of dengue infections has increased more than 30-fold in the past 50 years as urbanization gives the city-dwelling mosquitoes that spread the disease more places to breed. Brazil, which is hosting the World Cup this year and the Olympic Games in 2016, is among the hardest-hit countries, along with India, Indonesia, Vietnam and Mexico.

Other dengue vaccines are being developed by Inviragen, a subsidiary of Osaka, Japan-based Takeda Pharmaceutical Co., and by Merck & Co. and the U.S. National Institutes of Health.

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