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Promising Dengue Vaccine Against Haemorrhagic Fever

By Sakina Mohamed

KUALA LUMPUR, July 13 (Bernama) -- The results of the study on the much-anticipated dengue vaccine was released last Friday showing promising results, with nearly 90 percent efficacy against dengue hemorrhagic fever.

The French pharmaceutical company Sanofi revealed in a leading medical journal, The Lancet, the detailed results of Phase III of the trials conducted in five countries in Asia. Over two-thirds of the global figure on the mosquito-borne disease are recorded in the region.

The clinical trials are carried out on 10,275 healthy children aged 2-14 years old in Malaysia, Indonesia, the Philippines, Thailand and Vietnam.

It is the world's first large scale dengue efficacy vaccine study aimed at estimating the protection provided after the last of three injections, each spaced six months apart.

ECONOMIC IMPLICATIONS

It was found that the vaccine provided protection against dengue haemorrhagic fever by 80 percent after one or more injections, and 88.5 percent after three.

Malaysian virologist Emeritus Prof Datuk Dr Lam Sai Kit said this could translate into lower hospitalisation and healthcare costs since the vaccine could reduce the incidence of severe dengue by two-thirds, as well as prevent deaths.

The social impact on parents was immeasurable, said Dr Lam who is also the Immediate Past President of the Asia Pacific Dengue Vaccine to Vaccination Steering Committee.

He said a study using multiple data sources to estimate the cost incurred from the illness in Malaysia by the University of Malaya (UM) Medical Centre, in conjunction with Brandeis University, USA, showed that the economic burden of dengue in Malaysia is USD102(RM325) million per year, or approximately USD3.72 (RM11.85) per capita.

"Another study also by UM and Brandeis researchers was on the economic cost of dengue vector control, where the cost per capita was estimated to be USD1.70 (RM5.42).

"Using the present vaccine could be very cost-effective for the country," said Dr Lam, who is currently UM's High Impact Research Consultant.

Sanofi Pasteur, the vaccines division of Sanofi, disclosed in a press release on July 11 that the vaccine reduced dengue by 56.5 percent in the vaccinated group compared with the control placebo group, as observed during 25 months of active surveillance.

The data also showed good serotype specific protection, with better protection shown against DEN3 and 4 (75 percent), less against DEN1 (50 percent) and least to DEN2 (35 percent).

Dr Lam noted the percentage of efficacy against DEN2 was low but said this warranted further analysis.

"It is important to wait for the Latin American trials which involve over 20,000 volunteers and see whether this finding holds out," he said.

The second of the late-stage trials are being conducted in Brazil, Columbia, Honduras, Mexico, Puerto Rico on 20,000 children aged between nine and 16 years old. Its results would be published before the year end.

HOW EFFECTIVE IS IT?

Dr Lam noted that one of the points highlighted in The Lancet was that the efficacy of one dose of the vaccine was as good as three, in all the five countries where the trials were conducted. This could mean lower immunisation costs for what is likely to be a pricey vaccine.

He said that it might be related to the fact that the volunteers have existing antibodies due to the natural exposure to flaviviruses, including dengue.

"Further assessment needs to be done to see whether this result is consistent. If this is so, it will make the administration of the vaccine in dengue endemic countries much easier, and certainly less expensive," said Dr Lam.

The findings also implies that the vaccine works better in high dengue endemic countries because of the existence of pre-existing antibodies. It is also why it was more effective in older children as the group would likely have had previous exposure, he noted.

The vaccine would probably not be as effective on those from non-dengue endemic areas.

"A British tourist seeking immunisation against dengue before coming to Malaysia, for example, may get poor protection from the vaccine. However, we need to do a larger study on this before drawing any conclusions," he said to Bernama.

Dr Lam recommended vaccinating schoolgoing children first, especially those in secondary schools.

"It is a known fact that severe dengue is seen more in young adults, so by immunising secondary school students who are the high risk group for severe dengue, it will reduce cases of dengue haemorrhagic fever and death in the country," he said.

WHAT NEXT

Dengue, also known as "breakbone fever" due to the severe pain it can cause, affects nearly half of the world's population. The WHO says the disease infects some 100 million people yearly, while some experts put it at triple the figure.

There have been 46,681 dengue cases in Malaysia from January till early July this year, a 246 percent increase compared with the corresponding period last year. The death toll within the period stands at 87, a 222 percent increase from the same period last year.

"In the last 40 years since I first started doing research on dengue, it has increased 30 fold despite all the control measures. The present vaccine is giving us hope that we will have an additional tool to combat this global scourge.

"If the data from the Latin American trial support the Asian study, then one should seriously consider its use in Malaysia," he said.

-- BERNAMA




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