Sanofi announced last week that its dengue vaccine that was given to 730,000 children in the Philippines may pose health risks. The French drug company said that the vaccine may worsen the potentially fatal disease in those who were not previously infected.

First-Ever Approved Vaccine For Mosquito-Borne Dengue

The vaccine, Dengvaxia, is the first-ever approved vaccine for dengue. It can provide protection against all four strains of dengue. Earlier recommendations said that healthy individuals between 9 and 45 years old could be given the shot in 3 doses to be administered six months apart.

Sanofi, however, revealed last week that findings of a new long-term study suggest that while the vaccine worked with people who had a prior infection, it posed risk for those who had not.

Those who were not previously infected by the virus, more cases of severe disease may happen following vaccination once infected. The drug company said that it would ask health authorities to update information provided about the vaccine.

"Analysis confirmed that Dengvaxia provides persistent protective benefit against dengue fever in those who had prior infection. 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," Sanofi said in a statement.

In a press conference held on Monday, Sanofi medical director Ruby Dizon said that there had been no reported deaths linked to the dengue vaccine in the Philippines. Nonetheless, he assured that the company continues its monitoring efforts and is working with the Department of Health.

Dengue Fever

More than 400 million people worldwide get infected by dengue fever, a mosquito-borne disease. The World Health Organization said that the illness is one of the leading causes of serious illness and deaths among children in some Latin American and Asian countries.

The Philippine's DOH purchased PhP 3.5 billion or about $69 million worth of vials in early 2016. More than 700,000 Filipino youths have reportedly been vaccinated under the mass immunization program of the government. DOH said that of those who were inoculated, 70,000 are now at risk of more severe types of dengue about two years following their vaccination.

The South Asian country has launched an investigation and the public immunization program was halted on Friday. Authorities have already ordered the National Bureau of Investigation to probe the drug maker. Legislators are also set to investigate DOH's purchase of the dengue vaccine.