Bangkok: Philippine authorities are investigating the deaths of 14 children vaccinated in the world's first wide-scale dengue vaccine program amid growing fears about its safety and anger over its use on 837,000 children.
The administration of former president Benigno Aquino approved use of Dengvaxia in early 2016 to combat the potentially deadly mosquito-borne virus despite objections from government experts.
President Rodrigo Duterte's administration continued the vaccination drive after he took office in June 2016 despite a warning from the World Health Organisation.
Health researchers fear the scandal will stoke mistrust in vaccines across the world.
The Philippines stopped the sale and distribution of Dengvaxia late last year after its French producer Sanofi Pasteur warned the vaccine could worsen symptoms for people who had not been previously infected with the virus.
Dengue affects 390 million people globally every year and kills 25,000, mostly in Asia and Latin America.
The company's disclosure provoked a public furore in the Philippines with some parents blaming the vaccine for their children's deaths.
The Philippine Department of Health has revealed that at least 53 children who were given the vaccine still developed dengue "although they recovered or were on their way to recovery".
The government has assigned an independent panel of experts to investigate the deaths of the 14 children and report its findings within two weeks.
Health Secretary Francisco Duque told reporters that at least four of the children died of dengue.
"We need to watch out for 837,000 students who have been vaccinated and to us this is paramount," he said.
One death under investigation is that of 10-year-old Christine Mae de Guzman who suffered a throbbing headache one day after receiving a second dose of the vaccine.
Within days she had died, succumbing to dengue fever.
Christine's school in the province of Bataan, 100 kilometres north-west of Manila, was one of the first to take part in the vaccination drive.
"Of course we approved of it," Christine's father Nelson de Guzman told reporters. "It was for health."
The government has said it will sue Sanofi, accusing the pharmaceutical giant of failing to comply with Philippine Food and Drug Administration (FDA) guidelines.
It is also demanding a refund for $US70 million ($89 million) worth of unused Dengvaxia stock.
Sanofi maintains the vaccine does not kill people and that the drug is still effective for people who have previously contracted dengue.
The vaccinated children, aged nine or above, were not tested for previous dengue infection.
The company said in a statement it has complied with local regulations and FDA requirements and that it will continue to cooperate in full transparency with Philippine authorities, and to comply with the country's laws and regulations.
Dr Su-Peing Ng, head of the company's vaccine division, told reporters "there is no cause for alarm" and "those vaccinated in high-exposure settings are much more protected than those who were not."
Former president Aquino told a congressional hearing in December that the disease was a significant enough problem that he met with Sanofi executives twice before approving use of the vaccine.
More than 200,000 people contracted dengue in the Philippines last year, many of them children.
Doctors at the Philippine Department of Health had raised concerns over the lack of long-term safety data on its use before the program was launched.
Duterte has welcomed the investigations.
"If there is a failure let them sort it out," he said.
Dengvaxi has been introduced in 10 other countries but the Philippines is the only one to launch a mass immunisation drive.
The Brazilian government has said it will continue a trial in Parana, a southern state hard-hit by dengue epidemics, for children aged older than 15 but it would follow Sanofi's recommendation to avoid vaccinating people who have never had dengue.
The World Health Organisation, which published guidelines on how to use the vaccine in 2016, said it did not approve the mass vaccination program.
"This is a decision for governments and governments alone," said Dr Gundo Weiler, the WHO's representative in the Philippines.
Leonila Dans, an epidemiologist and paediatrician at the University of the Philippines, has described the vaccination program as devastating for the country, one of Asia's poorest nations with a population of 100 million.
"Even those who are not vaccinated are very emotional about it, because they feel for the kids who had the vaccine," she said.
Michel De Wilde, a former senior vice president of research and development at Sanofi, who oversaw the vaccine's development until he left the company in 2013, told the New York Times the program was a "huge disappointment and big lesson in humility."
The company spent decades developing the live-virus vaccine which is administered in three doses, taken six months apart.
Also called break-bone disease, dengue can cause high fevers, headaches, muscle and joint pains and lingering weaknesses.
Sometimes the disease causes hemorrhage or shock, which can be fatal.
