Sanofi SA (SASY.PA) attempted to allay concerns, saying in a statement that "the vast majority of those vaccinated to date live in high endemic settings and, therefore, will have had a prior dengue infection before vaccination".
Singapore's Health Sciences Authority said last week it had flagged risks when the vaccine was approved in October previous year, and that it was working with Sanofi to strengthen warnings in the packaging of the drug of an increased risk to vaccinated individuals not previously infected by dengue.
The Philippine Food and Drug Administration also directed Sanofi to conduct an information dissemination campaign and said all drug establishments should report any incidents if the vaccine was suspected to have caused any deaths or serious illnesses.
Sanofi said in late November that a new analysis based on six years' worth of clinical trial data showed Dengvaxia could worsen symptoms for those not previously infected with dengue.
World Health Organization acknowledged mid-April 2016 that these conditions appeared to be met in the three regions in the Philippines where the dengue vaccination program was already underway at that time - noting that the decision to roll out the vaccine had been taken by the DOH before WHO's advice became available. "Dr Joselito Santa Ana, the company's regional director, said: "'Severe' may just be two days of fever, lower platelet count, haematoma or vomiting".
Rene Catan may have felt vindicated by his decision to delay the implementation of the government's dengue vaccination program for Cebu's children early this year despite the insistence of local officials to proceed with it.
They have received at least one dose of the vaccine as part of a government program that cost 3.5 billion pesos ($69 million).
Health Secretary Francisco Duque III has assured that those responsible for the dengue vaccine mess would be held accountable.
The vaccine so far has been approved in 19 countries and launched in 11, Sanofi said.
The Philippines isn't alone in this as other countries like Brazil face a similar problem.
"The FDA is closely coordinating with the Department of Health for any adverse events/reactions that may be reported by the recipients following their immunization of Dengvaxia, and will immediately take appropriate measures to protect the public", it added.
However, who would have anticipated that the World Health Organization (WHO) which had previously endorsed the vaccine, would issue a November 30 advisory stating that only those who previously contracted dengue should be administered with Dengvaxia?
A spokesman for Singapore's Health Sciences Authority said last week that it is working with Sanofi to "strengthen the package insert" to include the warning of an increased risk of hospitalisation for dengue and clinically severe dengue in vaccinated individuals not previously infected.