MANILA - The Philippines has put on hold its 3.5 billion-peso (S$94 million) dengue vaccination programme, following an alert issued by French pharmaceutical giant, Sanofi Pasteur, that its Dengvaxia vaccine could prove harmful to people never infected by the mosquito-borne disease.
Philippine health officials began vaccinating over a million children in April last year (2016) with Dengvaxia, the world's first dengue vaccine, amid safety concerns expressed by public health advocates.
Sanofi recently sent out an alert saying: "For those not previously infected by dengue virus, the analysis found that in the longer term, more cases of severe disease could occur following vaccination upon a subsequent dengue infection."
Philippine Health Secretary Francisco Duque told a news briefing on Friday (Dec 1): "In the light of this new analysis, the Department of Health will place the dengue vaccination programme on hold while reviewed consultations are on the way with experts, key stakeholders, and…the World Health Organisation (WHO)."
At least 730,000 children have already received the first of three doses of the vaccine as of Nov 17.
Dr Duque allayed concerns over the vaccine's use.
"The vaccine has shown consistent and sustained benefits for those who were previously infected with the dengue virus...Let me underscore the fact the even for those who have not had prior exposure to dengue or never had dengue infection and received dengue vaccination, they have a protective period, which is 30 months," he said.
He said for those who received the vaccine, there has been a 93 per cent reduction in severity of symptoms, and an 82 per cent reduction in hospitalisation.
"I hope that this development will not, in any way, affect the expanded programme on immunisation because there are countless number of lives that have been saved from vaccine-preventable diseases. The value of that has to be preserved, and our vaccination programme has to be enhanced and strengthened, and we are committed to do exactly that," he said.
The health department, nonetheless, is reviewing its contract with Sanofi.
Dr Duque disclosed that the government has already paid 3 billion pesos for the 3 million doses it ordered from Sanofi.
The Philippines will await results of an inquiry by the WHO's Strategic Advisory Group of Experts on Immunisation later this month before moving forward.
"We want to know what 'severe disease' Sanofi is referring to. We want their official definition of what is 'severe'. It's not clear to us what constitutes a severe disease. So, we are awaiting their reply," said Dr Duque.
The health department has already instructed all its health care providers to monitor those who have received Dengvaxia, and tabulate and investigate cases that land in hospitals, regardless of symptoms.
The department will also be ramping up its five-year, post-vaccination surveillance programme by hiring more personnel.
The Philippine Food and Drug Administration, meanwhile, is proposing a labeling change for Dengvaxia.
The leaflets that come with the vaccine containing instructions for use will have to be amended to reflect Sanofi's latest alert before the product can be sold again.
Public health advocates had earlier urged the health department to delay the rollout of Dengvaxia, citing possible adverse effects.
Dr Antonio Dans, a professor at the University of the Philippines' College of Medicine, warned at the time that while the vaccine could reduce dengue cases, it could later increase the disease's severity, a phenomenon known as "antibody dependent enhancement".
Citing Sanofi's own studies, he said this could happen three years after the vaccine's introduction.
"The real dengue we are afraid of is severe dengue, not the mild ones. If a vaccine prevents mild disease but causes severe dengue, we shouldn't be using it at all," said Dr Dans.
Dengvaxia was developed by Sanofi after 25 clinical studies in 15 countries over 20 years.
The WHO has backed the use of the vaccine based on a review of the studies.