The Senate Blue Ribbon Committee and the Senate Committee on Health are investigating the Department of Health's P 3.5 billion immunization program that used Dengvaxia vaccine.
Former Health Secretary Janette Garin has been invited as among the resource speakers.
In her opening remarks, she stressed that the decision to purchase Dengvaxia from French pharmaceutical firm Sanofi Pasteur was not her decision alone.
She explained that it was an institutional decision as several government officials were involved in the negotiations.
Garin also said the Philippines was able to purchase the vaccine at a lower price.
She said while Brazil bought Dengvaxia at $30 per dose, the Philippines procured the vaccine at $20 per dose.
Aside from testifying in the Senate hearing, Garin is set to undergo operations for appendicitis later in the afternoon.
Dengvaxia was introduced to the Philippines in April 2016.
The vaccine was administered to about 830,000 school children.
Sanafi Pasteur recently announced Dengvaxia can cause severe reaction to persons who were given shots when they have not contracted dengue.