UNDER THE MICROSCOPE
The world is experiencing a rapid increase in temperatures, with heat records broken almost daily, due to the now-undeniable effects of climate change. With increasing hot weather comes the accompanying shifts in the seasons, when rainfall is increased and irregular in distribution.
With the erratic weather comes an increase in the number of dengue cases, as we recently experienced. With half the global population living in dengue-endemic areas, the burden of disease is higher in the Americas and Asia. An estimated 390 million dengue cases occur annually, with 96 million of these manifesting clinically. Dengue is a leading cause of hospitalization and death among children and adults in Latin America and Asia. Even the United States of America is experiencing a gradual creeping of dengue infections toward the northern regions, which used to be dengue-free.
There is a dire need to protect vulnerable populations from dengue. Control can be classified into factors affecting the virus, the mosquito vector or the human victim. Progress in virus control remains slow and has no practical application at the moment.
Vector control measures such as search and destroy habitats, fumigation and clean-up of mosquito breeding sites are not achieving results. Bioinsecticides and Wolbachia bacteria infection of mosquitoes are promising but are not yet in widespread use.
We are left with protecting the human from falling victim to the bite of a dengue virus-carrying mosquito. But no matter how we try to protect against mosquito bites, they seem to have a way of finding our soft spots and score a bite with the injection of dengue virus as a bonus.
Thus, the only real protection from this annual epidemic of dengue fever/hemorrhagic fever is vaccination. While the Dengvaxia vaccine had been licensed in many countries around the world, the Philippines struggles with the effects of vaccine hesitancy induced by the continuing Dengvaxia hysteria. The Philippine FDA withdrew the first dengue vaccine in spite of its high dengue burden.
Now, a second dengue vaccine has come in the market. The Takeda-developed Qdenga tetravalent vaccine (because it is designed to protect against all four strains of the dengue virus) is now licensed and in use in many countries, but continues to languish in approval limbo in its application with the Philippine FDA for the last two years. Why, in spite of many robust studies proving the efficacy and safety of the vaccine, which were surely submitted in support of its application for licensure, hasn’t convinced the movers and shakers of FDA, is surely a medical mystery worthy of some scientific sleuthing.
Thus, armed with several studies on the Takeda vaccine (disclosure: funded by Takeda), let’s take a look at the evidence for its efficacy and safety. These researches were published in The New England Journal of Medicine, Clinical Infectious Disease Journal of the Infectious Disease Society of America, and The Lancet, all prestigious medical journals of the highest integrity.
These randomized, double-blind and placebo-controlled researches were done in multiple countries in Latin America and tropical Asia, including the Philippines, where Dr. Lulu Bravo, pediatric vaccinologist, was the chief investigator and co-author of several of the published researches. The number of subjects were in the hundreds of thousands, which made for a robust conclusion statistically.
Unlike the Dengvaxia vaccine, Qdenga did not show any safety signals, and can be given to seronegative individuals (persons who have not had a previous dengue infection). Thus, it can be utilized in mass vaccination activities without having to determine a vaccinee’s serostatus.
In one study involving 20,099 individuals, the overall vaccine efficacy was 80.2 percent, which means it protected that percentage of vaccinated individuals compared to unvaccinated ones. Other findings were a vaccine efficacy of 76.1 percent in seropositive individuals, and 66.2 percent in seronegative individuals. More significantly, the Takeda vaccine has 90.4 percent protection against hospitalized dengue and 85.9 percent against dengue hemorrhagic fever. The other studies showed similar vaccine efficacies.
Translating these figures into actual scenarios, if the 390 million persons infected worldwide annually were vaccinated with the Takeda vaccine, it would have prevented almost 313 million cases, surely a huge savings in both human suffering and health resources! Assuming that the 96 million hospitalized dengue cases worldwide annually were vaccinated, over 86 million of them would have avoided hospitalization. It will be a boon for public health worldwide if dengue vaccination is implemented universally.
Locally, if the 340,860 cases recorded from Jan. 1 to Nov. 16, 2024, were vaccinated with the Takeda vaccine, only 67,490 individuals would have had dengue, and only 6,479 would have been hospitalized. It would have meant we wouldn’t be needing to set up dengue fast lanes in government hospitals and our health system would not be groaning under the heavy number of dengue cases consulting.
We needed that vaccine last year.