A vaccine for dengue fever developed by Sanofi has shown the potential to protect against three of the four disease serotypes in a mid-stage trial.

According to analysis published in healthcare journal The Lancet, Sanofi’s vaccine candidate was shown to be 61.2% effective against dengue virus type 1, 81.9% against type 3 and 90% type 4, but failed to provide any protection against serotype 2.

The study involved 4,002 children aged between four and 11 years old, with the children given three doses of the live, attenuated vaccine at zero, six and 12 months.

Despite the promising results for specific serotypes, the vaccine’s failure to provide protection against serotype 2 reduced the vaccine’s overall efficacy to 30%, significantly less than the 70% highlighted by researchers.

The study did, however, confirm the vaccine’s safety profile, and International Vaccine Institute spokesperson Dr Scott Halstead said that the test results should be a source of hope for parents whose children are at risk of dengue fever.

"The complexity of dengue virus infection has hampered vaccine research for decades. This is the first time in 50 years of dengue research that I have seen a vaccine that protected a large group of children from clinical disease caused by dengue viruses. Best yet, the vaccine met the highest safety expectations," said Halstead.

Whilst Sanofi has confirmed that analyses are ongoing to determine the lack of protection for serotype 2, further Phase III clinical studies of the vaccine are currently underway, involving 31,000 children and adolescents across 10 countries in Asia and Latin America.