Dengue fever is now like the flu, WHO chief says, calling on countries to consider ‘practical values’ of new vaccine
- Food and Drug Administration in US gives Dengvaxia the nod, but Hong Kong officials say it is not suitable for city’s residents
- Takeshi Kasai, the World Health Organisation’s new regional director, says disease is not containable
The World Health Organisation’s (WHO) top man in the Western Pacific region has called on dengue fever endemic countries to consider the practical values of the world’s first vaccine to fight against the mosquito-borne disease, given a significant spike around the region.
Dr Takeshi Kasai, who visited Hong Kong for the first time as the WHO’s new regional director earlier in May, said dengue fever should be managed just like seasonal flu.
“Dengue is not like in the past when you had a few cases then contained it,” Kasai said. “It is no longer that kind of disease. Dengue is now with us. It’s like seasonal influenza.”
Kasai met with Secretary for Food and Health Professor Sophia Chan Siu-chee, Director of Health Dr Constance Chan Hon-yee, and Centre for Health Protection controller Dr Wong Ka-hing during his stay, and exchanged views on measures to combat the spread of dengue fever in the city.
The Food and Drug Administration in the United States has approved a vaccine called Dengvaxia, which is designed to prevent the disease caused by all strains of the virus in children aged between nine and 16, but is only for those “who have laboratory-confirmed previous dengue infection and who live in endemic areas”.
Kasai said countries or territories should consider the vaccine’s effectiveness, and how “practically we can use this vaccine”.
He said doctors and hospitals must first check whether the child or adult had a prior dengue infection, as the WHO had advised the vaccine should not be given to people who had not previously been infected with the virus.
Kasai said cost was another consideration involved if vaccination was to be part of an anti-dengue strategy, as Dengvaxia was a three-part process with six months between each dose.
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“All those things need to be considered and the authorities need to consider whether this is an important tool for fighting dengue or not,” he said.
Kasai said the WHO position indicated the vaccine was “definitely an important tool, but needs to be contextualised”.
Dengue fever, which is mainly transmitted to humans through the bites of infective female Aedes mosquitoes, is estimated to cause 390 million cases per year and remains endemic in some areas of Asia, including the Philippines, Malaysia, Singapore and Thailand.
It can be mild on first infection but a second can be particularly severe, occasionally fatal, especially if they are different subtypes.
Symptoms include high fever, severe headache, pain behind the eyes, muscle and joint pain, nausea, vomiting, swollen lymph nodes and rash.
There has been a spike in dengue cases in Hong Kong, with 42 cases confirmed as of May 2, with nine each from Indonesia and Malaysia and seven from Thailand.
There were 24 cases between January and May 2018.
But a Health Department spokesman said Hong Kong would not be using Dengvaxia any time soon.
“With reference to the WHO’s latest recommendation, dengue vaccine is not suitable for the general population in Hong Kong because the local seropositive rate of dengue virus antibodies is just 4.6 per cent for the whole population according to a local study,” the spokesman said.
The WHO recommended vaccination be considered if seroprevalence rates were at least 80 per cent by the age of nine.
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The spokesman said the rainy season and hot weather were conducive to mosquito proliferation and breeding, and it had begun “an all-out anti-mosquito operation” on April 15, including fogging scrub areas within a 100-metre radius around homes weekly.
Sanofi Pasteur, which developed Dengvaxia, said its priority was to bring the dengue vaccine to at-risk populations to help combat and prevent dengue for those who had a prior infection.
Last summer, Hong Kong saw 29 locally acquired cases that were linked to two different clusters in Lion Rock Park and Wong Tai Sin, and Cheung Chau.
Those 29 cases were among a record 163 dengue cases last year, higher than the 30 to 124 cases per year from 2008 to 2017. Of that number, 134 were imported, mostly from Thailand, China and the Philippines.
