MANILA, Philippines (AP) " A Sanofi Pasteur official says the French drugmaker cannot comply with the Philippines' request for a refund of dengue vaccines injected on over 830,000 children because it would imply that the drug is ineffective.

Sanofi Pasteur Asia-Pacific chief Thomas Triomphe told a congressional hearing Monday that it's clear in "absolute terms" that the Philippines will be able to more effectively reduce dengue infections if it continues to use the Dengvaxia vaccine than if it halts its use.

Health Secretary Francisco Duque III has asked Sanofi Pasteur to refund the Philippines' payment for unused Dengvaxia as well as Dengvaxia used in a massive government immunization program that was stopped last year after Sanofi said a study showed the vaccine may increase the risks of dengue in people vaccinated prior to infection.