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Trials for a new experimental vaccine for dengue — a serious disease caused by mosquito bites — are two years in, and one Canadian expert said the news is "encouraging."
A study released at the start of February confirmed a single dose of the Butantan-DV vaccine prevented symptomatic dengue for two serotypes (DENV-1 and DENV-2) in children, adolescents and adults. It had 90 per cent efficacy against DENV-1 and 70 per cent efficacy against DENV-2.
Over the past two decades, an increase in dengue cases has been reported worldwide, according to the World Health Organization (WHO). A spike in infections from 2000 to 2019 has resulted in close to a historic high of over five million cases and more than 5,000 dengue-related deaths in over 80 countries.
Stephen Barr, a professor and researcher at Western University in London, Ont., recently told Yahoo Canada the experimental vaccine "holds promise as a valuable tool against dengue in countries where DENV-1 and DENV-2 are prevalent."
Barr added "it is very encouraging to hear that this protection was regardless of prior dengue exposure, in contrast to the Dengvaxia vaccine," the only vaccine currently available.
I am hopeful, as many dengue sufferers and travellers are, that this vaccine will become available globally.Stephen Barr
Barr said he's "hopeful" the vaccine will become available globally. However, it won't happen until more testing is done.
There has been no increased risk of severe dengue or deaths associated with the vaccine over the two years of testing, but the WHO recommended a longer-term follow-up of five years to better assess durability of protection and safety.
But what exactly are the risks of dengue and how could this new vaccine help? Here's what you need to know.
How and why does the virus spread?
Barr previously told Yahoo Canada there's no human to human transmission of dengue, and a person can only get infected from a mosquito.
"When a human gets infected from the bite of a mosquito, another mosquito has to feed on that infected person and then the virus will basically replicate and incubate in that mosquito for about eight to 12 days, after which it can then become infectious and infect another human," Barr said in January.
According to the Centers for Disease Control and Prevention, dengue viruses are spread to people through the bites of infected Aedes species mosquitoes. These are the same types of mosquitoes that spread Zika and chikungunya viruses.
The Public Health Agency of Canada (PHAC) previously told Yahoo Canada in an email that dengue is not endemic in Canada and there are no locally-acquired cases of the viruses. But Barr warned Canadians can still get infected if they're travelling to countries where dengue cases are present.
What are the symptoms of dengue?
According to the Government of Canada, infection with the dengue virus can cause severe flu-like symptoms.
In some cases, "it leads to dengue haemorrhagic fever, also known as severe dengue, which affects the body's vascular system (how blood moves through the body). This can lead to significant internal bleeding and organ failure."
It's a very serious disease. ... It's important you get medical attention.Stephen Barr
Barr said a person who gets infected can experience nausea, vomiting, rashes, aches and pain.
He added people who end up experiencing severe pain will often end up taking over-the-counter painkillers such as ibuprofen, which can worsen the disease because of these drugs' ability to interfere with blood clotting.
Is there a cure for dengue?
There is no treatment for dengue, Barr said, and the therapy used to treat it is mostly pain management to help control symptoms.
There are also no approved vaccine or medications that protect against dengue fever.
"It's been very difficult coming up with an effective vaccine against dengue," Barr previously shared. The only vaccine currently available is called Dengvaxia and it is only given to a person who has been infected in order for it to work. It's also only recommended to those aged six to 45.
While news of a new vaccine brings on hope, it'll likely be years before one is circulating in Canada. That's why it's important to take preventative measures.
Could the new vaccine help keep Canadian travellers safe from dengue?
Barr told Yahoo Canada in an email it's possible the vaccine will be approved "for targeted use in endemic regions within the next couple years," depending on the study results. "It is unclear if it provides protection against DENV-3 and DENV-4 serotypes, which are also highly prevalent in regions around the world," he noted.
If the vaccine "proves highly effective and does not require prior dengue infection, it most certainly would be able to protect Canadian travellers from complications from dengue disease," he added.
However, Barr said it's important to note that vaccines do not typically prevent infection; an infected mosquito can bite a vaccinated person and transmit the virus. "The vaccine will help prevent the virus from causing disease symptoms and/or severe complications from the disease," he said.
The level of protection can vary and depends on a person's immune system.
Barr also explained it's unlikely this would become a routine vaccine.
"As long as dengue remains rare in Canada, vaccination against dengue will likely be limited to those travelling to high-risk areas, much like the yellow fever vaccine."
How can I stay safe from dengue when travelling?
The only effective way for a person to stay safe from dengue is to prevent themselves from getting bitten by a mosquito — which can be difficult.
Barr recommended Canadians travelling to warm and tropical climates use insect repellent strong enough to keep mosquitos away, and to cover up any exposed skin.
People are recommended to wear:
Light-coloured, loose clothes made of tightly woven materials such as nylon or polyester
Long pants and tucked-in long-sleeved shirts
Closed-toe shoes or boots
A hat to keep mosquitoes at bay
"Typically at nighttime when people have their guards down, these mosquitoes can come and bite," Barr warned, adding mosquito nets around beds are also recommended.