Dengue vaccine expert questions age limit for Dengvaxia shots

ABS-CBN News

Posted at Mar 13 2018 02:20 PM | Updated as of Mar 13 2018 03:39 PM

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MANILA - French drug-maker Sanofi Pasteur's recommendation that its dengue vaccine, Dengvaxia, may be given only to people 9 years or older does not make sense for one of the world's leading experts on dengue research.

Scott Halstead, a leading figure in dengue research in the last 50 years, stressed that what's more crucial than age is the determination of a patient's history of dengue infection before administering Dengvaxia.

"Two 2-to-5-year-old and 9-year-old children are the same immunological continuum. They are not two different categories," he said in a Senate hearing, adding that the age limit could've been higher.

Halstead said he nearly "fell off his chair" when the Dengvaxia-maker recommended that the vaccine only be given to those aged 9 and older after a 3-year-review in 2015. This also prompted him to write a paper on this matter.

"When the 3-year review of Sanofi was published, I read 2-to-5 year-old children were hospitalized at a higher rate than the control group. If I'd been here, you would have seen me. I fell off my chair," he said.

"Sanofi's allegation that 9 years was a safe year because there are some intrinsic difference between 9-year-olds and younger, it simply did not fit the biology of the human species," the scientist added.

Halstead said he recommended that patients should be tested before administering Dengvaxia in order to exclude seronegatives, or those who have not been infected with dengue, as only those with previous dengue infection will benefit from the vaccine.

"That's why in my paper I made a suggestion that before Dengvaxia will be given there should be a blood test so that the people who are seronegative can be excluded," he said.

Health Secretary Francisco Duque III said ELISA tests, which can determine seronegatives and seropositives, have been available in the Philippines since the 1970's.

Halstead tried to forewarn Philippine authorities on the use of Dengvaxia vaccine on children who had never contracted dengue, but the government ignored him.

Dengvaxia was given to at least 830,000 children throughout the country. The Philippines spent P3.5 billion to purchase the French-made vaccines.

Senator Richard Gordon said the Health Department, given these warnings, should have exercised due diligence before proceeding with the mass vaccinations.

Halstead, for his part, said he was "astonished and upset" that the government mass vaccination program pushed forward. He said there is a safe vaccine against dengue but it is not yet available in the Philippines.