An estimated 400 million people contract dengue every year, with a large number of these cases in the tropics and subtropical countries. This mosquito-borne disease hasn’t been a major problem in the United States, so far.1 But with the incidence of dengue rising, particularly in pockets like Florida and states bordering Mexico, it is time to explore preventive measures, including vaccination.2 In fact, data from the National Resources Defense Council (NRDC) reveals that the two breeds of mosquitoes responsible for the spread of dengue fever are present in as many as 28 states in the country, maybe more. As good a reason as any to turn to a vaccine or other alternatives.3
For someone who has dengue, treatment is largely supportive therapy in a hospital environment. Since dengue fever doesn’t have any direct antiviral cure, prevention becomes vital.
What Makes Dengue Prevention A Challenge?
Unlike malaria and other illnesses that count mosquitoes as a vector, dengue mosquitoes do not bite you only at night. This means traditional preventive mechanisms like sleeping under a mosquito netted bed are no longer useful. These mosquitoes are found both indoors and outdoors and don’t seek out only stagnant or dirty water. In fact, your seemingly harmless indoor planter, clean water barrels, and even your dog’s water bowl could be a breeding ground.4
Another challenge lies in the diagnosis itself. Because many cases begin rather mildly and have symptoms easily mistaken for other illnesses like flu (fever, headache, painful joints), those infected often do not seek medical care. The dengue link to other symptoms like rashes, abdominal pain, or nausea is also easy to overlook. If left untreated, this makes you a carrier who can then cause the infection to be passed on to others occupants of your home. Unfortunately, by the time more severe symptoms like intense abdominal pain, mucosal bleeding, or a drop in blood platelet counts show up, others may already have been infected.5
WHO data on the disease is sobering. Around half a million people need hospitalization every year due to dengue fever. Of them, 2.5 percent succumb to their illness. Mortality rates among those with severe dengue were at one point north of 20 percent. And that’s just the officially reported numbers. Unreported cases could take that number even higher. Timely hospitalization and better awareness are improving these numbers, but there’s more to be done.6 So what is our defense against the fever?
Dengue Vaccine Offers Hope
Until recently, measures to avoid being bitten may have been the only way to prevent dengue fever. But all that changed in April 2016, when the WHO announced its endorsement of the world’s first dengue vaccine. Called Dengvaxia (CYD-TDV), the vaccine by Sanofi Pasteur has been in production since 2015 end. It is given in a 3-dose schedule, the first being the baseline dose, then a second at 6 months, and the last at 12 months.The vaccine is available for use in Mexico, the first country to approve its use, as well as Brazil, Costa Rica, El Salvador, and the Philippines.7
Phase III trials in Latin America, Asia, and the Caribbean found that it offered protection from 65.6 percent of the symptomatic dengue disease brought on by the four virus serotypes considered in the study during the 25 months of evaluation. When it came to severe dengue, the data was even more promising, with protection estimates of 93.2 percent. Further, the protection also meant prevention of 8 out of 10 hospitalizations due to illness among the vaccinated.8
Who Can Use It?
The vaccine can be administered to anyone between the ages of 9 and 45 years, or 9 and 60 years (if the license permits), but is recommended for use mainly in regions prone to the illness. The WHO, in addition, suggests that CYD-TDV should be used at a regional level based on how the epidemiological data for that area reads. Only places with “high burden” of dengue fever should look at vaccination. That’s because it may cause long-term risks of a more severe dengue infection in those vaccinated if the seroprevalence (previous infection by dengue virus) for that age group is under 50 percent. As such, the WHO does not recommend vaccinations in such places or groups. On the other hand, if seroprevalence is over 70 percent, they are ideal candidates for the vaccination.9
However, if you have had serious allergic reactions to any component of the vaccine in the past, have immune deficiency (acquired or congenital), symptomatic HIV infection, or impaired immune function with asymptomatic HIV infection, or are breastfeeding or pregnant, you should not take the vaccine.
How Long Are You Protected?
Studies investigating the duration of protection offered by the vaccination are still underway, but what is clear is a definite waning of protection over time. The first two years seemed to offer greater protection to those who were vaccinated than to those who were not.10 The interim results of a longer-term follow-up study on vaccinated children aged 9 to 16 showed that hospitalization risk from dengue remained lower for up to two years from the date that the third dose of the vaccination was administered.11
What If You’re Not Allowed To Be Vaccinated?
If the vaccine is not available where you live, or if you fall into one of the categories for whom vaccination is contraindicated by the manufacturer, there are some ways you can still protect yourself. In fact, the WHO recommends that vector control must be continued as before, with the vaccine acting as a complementary measure. Here are some easy to implement measures that can greatly cut down your risk of contracting dengue fever.12
- Cover any water storage containers at home
- Clean these water bodies and containers regularly (at least once a week)
- Use insecticides on any outdoor containers
- Dispose of solid waste in a hygienic manner
- Use mosquito repellents and wear long-sleeved clothing
- Get screens put on your windows to prevent mosquitoes from entering
|↑2, ↑5||Dengue Fever Makes Inroads into the U.S., Scientific American (2013).|
|↑3||Fever Pitch Mosquito-Borne Dengue Fever Threat Spreading in the Americas, NRDC.|
|↑6, ↑12||Dengue and severe dengue, WHO.|
|↑7||SANOFI PASTEUR DENGUE VACCINE FREQUENTLY ASKED QUESTIONS, Sanofi Pasteur.|
|↑8, ↑11||Hadinegoro, Sri Rezeki, Jose Luis Arredondo-García, Maria Rosario Capeding, Carmen Deseda, Tawee Chotpitayasunondh, Reynaldo Dietze, H. I. Hj Muhammad Ismail et al. “Efficacy and long-term safety of a dengue vaccine in regions of endemic disease.” New England Journal of Medicine 373, no. 13 (2015): 1195-1206.|
|↑9||Dengue vaccine: WHO position paper – July 2016, WHO.|
|↑10||Dengue vaccine: WHO position paper – July 2016, WHO.|