MANILA - Health officials who signed a multibillion-peso deal to procure anti-dengue vaccine for public school students should be held liable after the vaccine company announced possible risks of the drug, senators said Saturday.

"We should hold the appropriate Department of Health officials responsible for haphazardly allowing the vaccine to be administered to students, without extensive due diligence on the effects of the drugs and without waiting for the results of comprehensive clinical trial," Sen. Joel Villanueva said in a statement.

In December 2015, the Philippines became the first country in Asia to approve the dengue vaccine for individuals aged 9 to 45.

On the same year, the DOH procured P3 billion worth of Dengvaxia intended for 1 million public school children in areas reported to have the highest incidence of dengue.

The Dengvaxia vaccine is said to be capable of lowering severity in dengue cases by 93 percent and reducing hospitalization rate by 82 percent, health officials said.

But vaccine manufacturer Sanofi Pasteur on Wednesday reported that Dengvaxia should not be recommended to individuals who have never been infected with the dengue virus.

It warned that the vaccine may cause "more severe dengue cases" on those who may contract the disease for the first time.

• DOH on alert as Sanofi admits dengue vaccine poses risks

"Sanofi should also be made accountable for their haphazard release of the drugs without complete and proper clinical studies," Villanueva said.

Sen. Richard Gordon, who called for a Senate probe on the procurement of the vaccines last year, said Sanofi's admission of Dengvaxia's risks proves that the vaccine procurement under the Aquino administration was a "midnight deal."

"When the Aquino administration procured it and the DOH proceeded to inoculate 280,000 children initially, the vaccine was not yet ready for distribution. Now we have the evidence on that," Gordon said in a statement.

"Before we conducted an investigation on the anomalous procurement of this vaccine, we talked to several health experts and they told us that they had already warned government long before about the possible adverse effect of the new drug on individuals with no prior history of dengue," he said.

The Philippine government suspended its dengue immunization program for public school students shortly after Sanofi announced Dengvaxia's possible risks.

• Philippines suspends dengue vaccine program after Sanofi warns of risks

On Friday, Health Secretary Francisco Duque III said no cases of "severe dengue infection" have been reported yet out of least 700,000 Filipino children who were given the vaccine.

• DOH: No severe infection among PH kids given dengue vaccine

As of November 2017, about 733,713 Filipino children have been given the anti-dengue vaccine. At least 789,010 units of Dengvaxia, most of which will expire next year, have yet to be used, the DOH said.