Virologist urges govt to provide access to new dengue vaccine

VIROLOGIST and emeritus professor Datuk Dr Lam Sai Kit has urged the government to provide access to a new dengue vaccine suitable also for individuals previously infected with dengue.

Unlike the Dengvaxia vaccine developed by Sanofi Pasteur and cleared for marketing in 2015 (but not in Malaysia), there is no requirement for pre-vaccination testing as the new Takeda (TAK-003) vaccine, also known as Qdenga, has been approved for use regardless of prior dengue exposure.

“Globally, an estimated 3.9 billion people, about half the world population, are at risk of dengue, and it is now endemic in more than 125 countries.

“According to the World Health Organisation, there are an estimated 390 million infections and 500,000 hospitalisations each year.

Dr Lam, who is also a research consultant at Universiti Malaya, said dengue is the fastest-spreading mosquito-borne virus and was recognised by WHO in 2019 as one of the ten threats to global health.

The worldwide incidence of dengue has risen eight-fold in the past 20 years and is still rising, due to climate change, rapid urbanisation, population growth, inadequate waste management and improper water storage.

“This provides breeding grounds for these mosquitoes, facilitating the transmission of the dengue virus.”

Dengue is an important public health problem in Malaysia. In 2023, the Health Ministry said that the cumulative number of dengue cases reported up to ME48 (epidemiological week) increased by 91.3%, to 111,417 cases, compared with 58,239 for the same period in 2022.

A total of 84 deaths due to dengue fever complications have been reported, compared to 39 deaths for the same period in 2022.

“Despite an intensified integrated vector control programme in the country, including the use of Wolbachia-carrying Aedes mosquitoes in hotspots in the Klang Valley, the number of dengue cases has not declined significantly.

“Developing a safe dengue vaccine that will give lifelong protection against all four serotypes, and be affordable for developing countries where the disease burden is the greatest, has been a priority programme for international agencies, including WHO,” said Dr Lam.

He said developing a vaccine against all four dengue serotypes has been a challenging task and has been ongoing since the 1950s.

There are four dengue serotypes (Den 1-4) and infection against one serotype will not protect against infection by the other three serotypes.

“As a matter of fact, in some cases, previous exposure to dengue, through infection or vaccination, can lead to a more serious disease such as dengue hemorrhagic fever and dengue shock syndrome on second or subsequent infections.

“Hence, we are looking for a vaccine that will give lifelong protection against all four serotypes equally,” added Dr Lam, a senior fellow with the Academy of Sciences Malaysia.

In addition, he said, the vaccine must be affordable for developing countries where the disease burden is the greatest. Safety is an important issue, and the vaccine should not increase the risk of severe diseases in individuals with pre-existing immunity, added Dr Lam.

Based on data provided by Takeda, the European Union approved the licensing of Qdenga in October 2022 and it is available for European tourists who travel to Latin America, the Caribbean and Southeast Asia.

Qdenga is currently available for children and adults in the EU, UK, Indonesia, Thailand and Brazil. – The Vibes, January 15, 2024