From Meer Ahmad Mydin Meera via email
Debates on the safety and efficacy of Dengvaxia, the world’s first anti-dengue vaccine, largely involve quarters who seem lost in the woods because they pay too much attention to the trees.
Of course, we can wait for the World Health Organisation (WHO) to give its Position Statement on the issue before deciding whether we should use the vaccine. That statement is due next month, but why would anyone expect it to be any different from the recommendations made last April by WHO’s Strategic Advisory Group of Experts (SAGE) on Immunisation? (See this report.)
From SAGE’s recommendations, it is obvious that there is little cause for concern about the safety of the vaccine.
Furthermore, several medical journals have reported that “Phase 3” trials of the vaccine have given positive results. (In a Phase 3 clinical trial, a drug or treatment is administered to large groups of people to confirm its effectiveness, monitor side effects, compare it to commonly used treatments and collect information that will allow the drug or treatment to be used safely.)
The New England Journal of Medicine, for example, reported that Dengvaxia “confers an overall average of 66% protection against dengue infection, 93% protection against severe dengue and 80% protection against hospitalisation for dengue” for the age group that was under study. It added: “Those who had been previously exposed to dengue had an even higher protection rate against reinfection – 82% versus the 52.5% protective effect for those who had not previously had dengue.”
The results of our own Phase 3 trial done in Malaysia are not much different. Our study, though, found that the protectiveness was slightly higher in subjects given only one dose than in those given the recommended three doses.
Singapore has decided against the use of the vaccine for the reason that the best protection it offers is against two of the less prevalent strains of dengue in that country. That decision is wrong. What matters is the overall protectiveness, especially against severe dengue and hospitalisation, and not the protectiveness against individual strains because mild dengue is no more severe than mild flu.
The vaccine can be introduced into Malaysia in either of these two ways:
- As specific protection of individual citizens at risk in endemic and hyper-endemic areas in the country paid for by themselves for themselves and their children;
- As a government-sponsored vaccination programme aimed not only at providing specific protection in endemic and hyper-endemic areas, but also at increasing the herd immunity in these areas and maybe nationally.
Most of SAGE’s recommendations appear to be towards introducing government-sponsored vaccination programmes.
Whichever way is chosen, the Ministry of Health must not hesitate to introduce the vaccine in areas of endemicity and hyper-endemicity where the seroprevalence rate is more than 50%. (“Seroprevalence” is defined in Wikipedia as the number of persons in a population who test positive for a specific disease based on blood serum specimens.)
To quote the Director-General of the Health Ministry, “One of the greatest medical achievements in modern civilisation is vaccination. Infectious diseases that were common less than a generation ago have become rare, thanks to vaccination. Countries around the world invest heavily in vaccination programmes.”
Dr Meer Ahmad is a public health consultant and general practitioner and former Assistant Director of Medical Services, Malaysian Army.
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