WHO to review Sanofi’s dengue vaccine Dengvaxia over safety concerns

The World Health Organisation (WHO) has ordered a review of Sanof's dengu vaccine, Dengvaxia, a year after it approved the world's first dengu vaccine in 2016.

Designed to protect people in the age group of 9-45, this vaccine, developed by France-based Sanofi Pasteur, is now reported to be causing more harm than good to people not affected by the virus.

Earlier, in the year 2016 the World Health Organisation had recommended the usage of Sanofi's dengue vaccine to control Dengue. However, WHO is now keen on reviewing Sanofi's safety data for the dengue vaccine.

The Mexican government was the first to approve the vaccine called Dengvaxia, in 2015. 

The review comes after Philippines halted a massive dengue fever vaccination effort and launched an investigation into the approval of Dengvaxia.

The Philippines has suspended its large-scale dengue vaccination effort amid the surprising results of a new study conducted by the vaccine's manufacturer.

On Wednesday last, French pharmaceutical giant Sanofi Pasteur published clinical trial data showing that its dengue vaccine, Dengvaxia, could have unintended consequences in patients who had never been infected with the mosquito-borne virus.

"The analysis confirmed that Dengvaxia provides persistent (protective) benefit against dengue fever in those who had prior infection," Sanofi said in a statement. "For those not previously infected by dengue virus, however, the analysis found that in the longer term, more cases of severe disease could occur following vaccination upon a subsequent dengue infection."

''The risk of hospitalised and severe dengue is significantly increased among vaccinated subjects who were seronegative for dengue at the time of first vaccination in all age groups studied,'' says the WHO report concerned with the safety of the drug. ''WHO believes that the safety of the drug may pose a threat to people who had not been exposed to the dengue virus previously, ie, before being vaccinated with Dengvaxia.

Owing to the safety concerns WHO will conduct a full review of the data through the Global Advisory Committee on Vaccine Safety and Strategic Advisory Group of Experts on Immunisation (SAGE). After which it will issue the revised guidance of the use of the vaccination.

While the WHO's Strategic Advisory Group of Experts on Immunisation (SAGE) had recommended the usage of Sanofi's dengue vaccine to control the widespread of the life-threatening Dengue, WHO had kept its stand by saying, ''The two candidate vaccines in phase 3 clinical development differ significantly from Dengvaxia so that no conclusions on the safety and efficacy profile of these candidates should yet be drawn. However, it will be necessary to carefully monitor vaccine performance over time in both seronegative and seropositive subjects.''

The main control measures for dengue to date have been to reduce the numbers of mosquitoes by large-scale spraying of insecticides. The chemicals have been deployed in both residential and public spaces in a mass culling of the insects spreading the disease.

Urbanization has aided the spread of dengue, with more than 100 countries now endemic for the disease. Pictured, containers, bottles and tires are perfect breeding sites for Aedes aegypti mosquitoes that transmit the dengue virus. The versatile mosquitoes can lay eggs on any shallow surface of water.

Public spraying of insecticides is based on seasonal changes, with more cases expected during rainy seasons in the tropics. But the measures haven't proven to curb the spread of disease adequately.

Experts believe a vaccine is needed to truly control the disease. A dengue vaccine, called Dengvaxia, recently became available in Mexico, Brazil, the Philippines and El Salvador.

Dengue virus is carried by the Aedes aegypti mosquito, the same type that can spread Zika virus. A bite from a mosquito harboring the virus can result in headaches, rashes and severe joint pains. In serious cases, it can cause internal bleeding and death.

The Philippines has halted a massive dengue fever vaccination effort

The country has launched an investigation into the approval of Dengvaxia. The Philippines suspended its large-scale dengue vaccination effort amid the surprising results of a new study conducted by the vaccine's manufacturer.

On Wednesday, French pharmaceutical giant Sanofi Pasteur published clinical trial data showing that its dengue vaccine, Dengvaxia, could have unintended consequences in patients who had never been infected with the mosquito-borne virus.

"The analysis confirmed that Dengvaxia provides persistent (protective) benefit against dengue fever in those who had prior infection," Sanofi said in a statement. "For those not previously infected by dengue virus, however, the analysis found that in the longer term, more cases of severe disease could occur following vaccination upon a subsequent dengue infection."