Getting ahead of Dengue
A new vaccine against the deadly mosquito-borne disease is waiting approval form Thai drug regulators
Dengue has been part of Thai life for so long that few gave it a second thought until last year, when young actor Tridsadee “Por” Sahawong was hospitalised with the most severe form of the viral disease. More than two months after contracting dengue haemorrhagic fever and undergoing multiple surgeries, he died early yesterday morning.
The dengue epidemic was particularly bad last year with more than 4,000 cases reported in the first few months alone.
The actor developed the virus at the end of October. The first the public knew of his illness was in early November when a plea went out online for platelet donations following his transfer from a local hospital to Ramathibodi Hospital after falling into a coma. The doctors amputated his left foot below the ankle and removed his left lung to contain infection as complications from the illness spread.
His illness, while rare in its severity, brought dengue firmly into the spotlight and today Thais are taking some precautionary measures to avoid getting bitten by mosquitoes and heading to hospital for a blood test should they develop a high fever rather than taking a couple of paracetamol and staying at home.
“It’s very sad that the actor should have become so ill. But what people forget is that Thailand has been dealing with severe dengue infections for decades. In some years, we have seen more than 100,000 cases and hundreds have died,” Professor Usa Thisyakorn, a paediatrician at Chulalongkorn University, said in an interview last week.
Around 170 scientists and doctors from Asia and Europe gathered in Bangkok last week for the inaugural Asia Dengue Summit where they exchanged important developments and updated strategies for improving dengue prevention and control for the region.
The summit was organised by Asian Dengue Vaccine Advocacy (ADVA), a scientific working group dedicated to dengue vaccine advocacy in Asia, with the aim of disseminating information and making recommendations on dengue vaccine introduction strategies in Asia.
ADVA was set up in 2011 to identify opportunities and make practical recommendations for improving surveillance and laboratory capacity for dengue disease confirmation.
“We can’t wait any longer as people are increasingly getting sick. Besides, the dengue strains are continuing to spread due to urbanisation as well as environmental factors that allow conditions ideal for the dengue mosquitoes to breed,” added Professor Usa, who is the chairwoman of ADVA.
Thus the recent approval of the world’s first dengue vaccine couldn’t have come at a better time and in some countries, it is already being given as protection against the infection that the World Health Organisation (WHO) has called “one of the most severe mosquito-borne viral diseases in the world”.
In the last 50 years, dengue has become endemic in 128 countries, where about 4 billion people live. Around 75 per cent of the infections occur in Asia and most are in Southeast Asian countries. According to WHO, more than 740 people around the world are infected by dengue every minute. The severe dengue haemorraghic infection, sometimes called Dengue Shock Syndrome, affects most Asian and Latin American countries and new dengue strains are capable of infecting adults, unlike earlier strains, which affected mainly children. The new strains could be fatal if contracted by menstruating or pregnant women.
Mexico has already launched its vaccination campaign and the Philippines recently became the first Asian country to get the approval for the vaccine though it is yet to start giving it. In Thailand, the vaccine has been submitted to the Food and Drug Administration for approval. The new vaccine is expected to protect against four dengue strains found in Thailand.
Even though the vaccine has been approved and its efficacy proved, Dr Usa says that the summit has to discuss the best methods of surveillance for the infection.
“We know the vaccine has only a 60-per-cent efficacy in preventing dengue so we need to be cautious,” she says.
Clinical studies carried out on the vaccine involved more than 30,000 children aged two to 14 years in Asia and nine to 16 years in Latin America. In Asia, the study was done in Vietnam, the Philippines, Indonesia, Malaysia and Thailand while Mexico, Colombia, Brazil, Honduras and Puerto Rico made up the test sites in Latin America.
The vaccine course is comprised of three injections with follow up carried out one year after the last injection showing that the vaccine had been effective in 60 per cent of the cases, Moreover its efficacy varies according to the type of dengue strain.
But the vaccination will definitely help in reducing numbers particularly in epidemic situations.
“I really do hope that it is given for free under our healthcare policy,” Professor Usa says, adding that the price is yet to be announced.
Work on developing a vaccine has been going on for several years. In Thailand the late Professor Dr Nut Pamornprawat from Mahidol University led the Thai research team as the first to develop the Chimeric live-attenuated vaccine.
The new dengue vaccine has been developed by Sanofi Pasteur.