A second thought on the dengue vaccine
Should we give a second thought in continuing the implementation of the school-based dengue vaccine program?
Earlier this month, the Department of Health (DOH) started to roll out the nationwide administration of the first dengue vaccine, which is marketed under the brand name Dengvaxia.
It is the product of more than 20 years of laboratory and clinical researches, involving a total of 40,000 volunteers, of whom 29,000 received the vaccine. The clinical trials were done in several Asian and Latin American countries wherein this mosquito-borne infection is endemic; and the Philippines was involved in all phases of the clinical trials.
The vaccine completed the final phase of clinical studies in 2014, and was approved by the respective Food and Drug Administrations of the Philippines and Mexico. Registration approvals in other countries are said to be forthcoming.
Impressive figures
Based on a media statement issued by Sanofi Pasteur, the manufacturer of the vaccine, pooled results of clinical trials evaluating the vaccine’s effectiveness and safety showed that it reduced dengue due to all four serotypes in two-thirds of the participants and prevented eight out of 10 hospitalizations and up to 93 percent of severe dengue cases.
These figures are indeed impressive at first blush. And since dengue fever imposes a huge disease burden in the Philippines, one can understand the enthusiasm of our health officials to immediately administer it nationwide to children aged 9 years and older, on a school-based program.
Is the enthusiasm to be the first country to administer it as part of the government’s vaccination program well thought out and judicious?
Urgent medical priority
Dr. May Book Montellano, president of the Philippine Foundation for Vaccination, was quoted in a statement issued by Sanofi Pasteur, as saying that prevention of dengue is an urgent and growing medical priority in the Philippines.
“Vaccination is widely accepted as one of the most cost-effective ways to reduce the spread of infectious diseases like dengue,” she said. “The approval of Dengvaxia, the world’s first dengue vaccine, in the Philippines, will be a critical addition to the ongoing public education and vector control efforts currently directed toward dengue prevention in our country.”
If there were no “red flags” in the extensive clinical trials done on the vaccine, I would have highly commended the sense of urgency of our health officials to immediately administer it publicly, as it would not be justifiable to withhold something that can spare the lives of thousands of our children and adults afflicted with severe dengue.
Safety questions
However, a closer scrutiny of the published study in the September 24, 2015, issue of the New England Journal of Medicine (NEJM), which I believe was one of the major bases for the registration approval of the vaccine, suggests that there are questions on its long-term safety, particularly on Year 3 after the vaccine had been administered. Hence, I share the grave concerns on the vaccine of highly credible health advocates including Doctors Willie Ong, Tony Dans and Tony Leachon.
Even the authors of the NEJM study acknowledge that they do not have the answers to these hanging questions and hopefully, continuing monitoring of cases and other ongoing studies should be able to provide the answers later on.
On the effectiveness aspect, the authors reported that the vaccine showed “a reduction in dengue disease in the efficacy surveillance phase among children who received the vaccine. In addition, there was a lower risk of hospitalization for dengue overall for up to two years after completion of the three-dose vaccination schedule among children between the ages of 9 and 16 years.”
However, the authors of the study also cautioned that “this reduction in risk was not observed among children under the age of 9 years.” They also reported that there were more hospitalizations and cases of severe dengue reported among participants under the age of 9 years than among those older than 9 years of age in the vaccine group, the clinical pattern of these cases during the long-term follow-up safety phase was similar to that reported for hospitalization during the efficacy surveillance phase, with no observed differences in clinical severity or viremia. In all cases, the participants had a complete recovery.
No definitive answers
Why is the vaccine not effective and could even be potentially harmful in children younger than 9 years? What can explain the paradoxical increase in severe cases of dengue by Year 3 in those who were vaccinated?
No one can offer definitive answers for now. “Available clinical data are insufficient for drawing definitive conclusions about the observed imbalance in younger children,” the authors wrote in their report.
Incidentally, our very own Dr. Maria Rosario Capeding of the Research Institute for Tropical Medicine in Alabang, is one of the lead authors of this landmark study. Amid the current raging controversy questioning the haste in publicly administering the vaccine, she can perhaps offer firsthand information and insights that can guide Health Secretary Janette Garin and the Department of Health (DOH) whether to proceed or suspend the ongoing dengue vaccination program.
While writing this commentary, it just occurred to me that sincere efforts at addressing the dengue problem seem to be the bane of health officials. Former Health Secretary Enrique Ona got into trouble for approving clinical trials in DOH hospitals that would evaluate an herbal treatment for dengue fever which showed promising preliminary results. Secretary Ona resigned after justifying his decision, but Secretary Garin canceled the approval and slammed the breaks on the clinical trials which had already started.
Now, Sec. Garin seems to be placed in a similar situation with health advocates expressing concern on the DOH’s undue haste in procuring and administering a vaccine with some questions (from its own researchers) on its selective effectiveness (only for children 9-16 years) and its long-term safety (paradoxical increase in severe dengue cases on Year 3).
I have heard from many that Secretary Garin is decisive. That’s generally a good trait for a leader. But, taking a pause, and giving crucial decisions a second thought and suspending one’s own decisions until valid concerns are satisfactorily answered, is the better half of decisiveness.
