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 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."
The company said it would ask the authorities in countries where it has been approved for use, including in Singapore, to update their information on the vaccine, and to disseminate it to doctors and patients.
A spokesman for the Health Sciences Authority in Singapore on Thursday said it was working with Sanofi Pasteur 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 by dengue.
The insert would also contain advisories on an assessment of prior dengue infection in individuals before vaccination, and that vaccination should not be recommended to individuals who have not been previously infected with dengue.
In Manila, the Philippine Health Secretary Francisco Duque told a news conference yesterday: "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 in the Philippines have received the first of three doses of the vaccine as of Nov 17. Dr Duque tried to allay concerns over the vaccine's use, saying that for those who received it, 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 have been countless lives 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 three billion pesos for the three 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 healthcare 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 labelling change for Dengvaxia 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".
Dengvaxia was developed by Sanofi after 25 clinical studies in 15 countries over 20 years. WHO has backed the use of the vaccine based on a review of data from the studies.