Dengue is a viral infection transmitted by the Aedes mosquito for which there is no specific treatment.
Early detection and access to proper medical care lowers fatality rates, particularly for severe dengue.
Dengue prevention and control depends on effective mosquito control measures.
Despite the public health measures at mosquito control, the reported incidence of dengue has been more than 100,000 annually since 2014, compared to 20,000-43,000 cases annually in 2011-2013.
The deaths in 2014 to 2016 ranged from 215 to 336 annually, compared to 35-92 annually in 2011-2013.
The advent of the dengue vaccine is an addition to the public health measures to prevent and control the infection.
It does not do away with the need for mosquito control as it is not a magic bullet.
What are the benefits and risks of the vaccine?
The World Health Organization (WHO) stated in its position paper that, “Vaccine efficacy varied by country ranging from 31% in Mexico to 79% in Malaysia.”
The efficacy against hospitalisation from dengue in those more than nine years old was 81 out of 100 patients, and against severe dengue, 93 out of 100 patients. (Source: WHO; Dengue vaccine – Position paper. Weekly epidemiological record No 30, July 29, 2016, page 357).
The safety profile of the vaccine to date has been benign.
In the Asian study, 1% of vaccine recipients and 1% in the control group had serious adverse events that happened within 28 days of vaccination. These events were mainly infections and injuries.
Vaccination is the cheapest method of disease prevention and control of infections.
Dengue and its vaccine have been the subject of economic analysis as part of the vaccine’s public health impact.
A research team at University Malaya studied the cost of mosquito control activities in 2010, when there were 46,171 dengue cases.
They concluded: “In 2010, Malaysia spent US$73.5mil (RM310mil) or 0.03% of the country’s GDP on its National Dengue Vector Control Program.
“This spending represented US$1,591 (RM6,712) per reported dengue case and US$2.68 (RM11.31) per capita population.
“Most (92.2%) of this spending occurred in districts, primarily for fogging.
“The inclusion of preventive activities increases the substantial estimated cost of dengue to US$176mil (RM742.46mil), or 72% above illness costs alone.
“If innovative technologies for dengue vector control prove efficacious, and a dengue vaccine was introduced, substantial existing spending could be rechannelled to fund them.” (Source: P. Raviwharmman Packierisamy et al. Cost of Dengue Vector Control Activities in Malaysia. Journal of American Society of Tropical Medicine and Hygiene. September 28, 2015)
The Strategic Advisory Group of Experts of WHO considered the comparative mathematical modelling evaluation of the potential public health impact of the introduction of the dengue vaccine by seven different groups.
They concluded: “All models predicted that routine vaccination of nine-year-olds with the dengue vaccine at 80% vaccine coverage would cause an overall reduction in dengue disease in moderate to high transmission intensity settings (SP9≥50%). For reference, this range of transmission intensity covers all the sites selected for the phase III trials.
“The impact of vaccination was greatest in high transmission intensity settings (SP9≥70%), where the reduction in DENV-related hospitalisations predicted by the models ranged from 10% to 30% percent, with 20% being an approximate central value.” (Source: WHO. Comparative modelling of dengue vaccine public health impact, March 17, 2016).
A research team at University Science Malaysia (USM) studied the economics of the introduction of the dengue vaccine.
“A dengue dynamic transmission mathematical model was employed to evaluate the impact of a dengue vaccination programme on the incidence, mortality and economic burden of the disease.
“The model was calibrated and validated with Malaysia-specific epidemiological data and vaccine efficacy data from phase III efficacy studies.
“The impact was evaluated over a 10-year period from provider perspective.
“Two vaccination strategies, targeted hotspots (THS, covered population in six selected hotspot districts) and nationwide (NW, covered the whole Malaysian population), were simulated.
“Both strategies comprised of routinely vaccinated children aged 13 and a catch-up cohort from ages 14 to 30 who were vaccinated over a one-year duration.”
The USM team reported that the “cost per dengue case from provider perspective was US$999.02 (RM4,214). The model predicted that dengue vaccination under the THS strategy would prevent 448,124 dengue cases, 509 dengue-related deaths, 11,785 life years lost and 16,751 disability-adjusted life years (DALYs).
“Nationwide vaccination would prevent 1,060,222 dengue cases, 1,202 dengue-related deaths, 27,834 life years lost and 39,584 DALYs.
“The total dengue treatment cost saved for THS and NW vaccination strategy were approximately US$163,859,846 (RM 691,242,760) and US$386,962,641 (RM 1,632,401,901) respectively.”
The USM team concluded that “dengue vaccination would significantly reduce the disease and economic burden in Malaysia, especially if it is introduced during current dengue epidemic”. (Yeo et al. Potential health and economic impact of introducing a dengue vaccine in Malaysia: Assessment using dynamic transmission modelling. Value in health (2015) Volume 18 Issue 7, page A582)
Whither the vaccine
The media reported on April 7 that the Drug Control Authority had approved the registration of the dengue vaccine and that it would be available within six months. Since then, there has been a paucity of news.
In the meantime, dengue continues to afflict the population with the Health Ministry’s report of 66,906 cases and 149 deaths in 2017, as at Sept 9.
There are obviously high direct costs due mainly to hospitalisations and indirect costs due to loss of work productivity among those affected.
Opportunity costs of time also add to the economic impact of dengue. Furthermore, it would be challenging to quantify the suffering of patients with dengue in monetary terms.
Potential patients, their families and doctors who have to manage patients with dengue, quite rightly, are wondering when the dengue vaccine will be available to blunt the human and economic costs of the deadly infection.
Dr Milton Lum is a past president of the Federation of Private Medical Practitioners Associations, Malaysia, and the Malaysian Medical Association. The views expressed do not represent that of any organisation the writer is associated with. The information provided is for educational and communication purposes only and it should not be construed as personal medical advice. Information published in this article is not intended to replace, supplant or augment a consultation with a health professional regarding the reader’s own medical care. The Star disclaims all responsibility for any losses, damage to property or personal injury suffered directly or indirectly from reliance on such information.