A global dengue outbreak of 500 million cases with over 5,000 deaths was reported in 2023 from 80 countries in every region of the world except Europe. The surge of dengue cases seen in 2023 is part of a global phenomenon fuelled by the climate crisis.
Brazil alone reported 364,855 dengue cases in the first five weeks of 2024, four times more than the same period in 2023. Three Brazilian states have declared emergencies and have begun to roll out the dengue vaccine.
Malaysia is no exception to this wave of dengue fever. A total of 123,300 dengue cases were reported in 2023, resulting in 100 deaths, compared to 66,102 cases, with 56 deaths in 2022. This is a humongous 86 per cent and 78 per cent increase in dengue cases and deaths.
I am sure that virtually every person have either had dengue or whose family member or friend had dengue, or was hospitalised for it, or suffered from complications of the disease or succumbed to the disease syndrome.
Therefore, the awaited conditional approval of Takeda’s Qdenga dengue vaccine by the Drug Control Authority (DCA) is a most welcome breakthrough, an invaluable armamentarium in our war against dengue.
Even though the overall efficacy (61.2 per cent) is not as high as the efficacy of most paediatric vaccines we are familiar with, the dengue vaccine nonetheless demonstrates a profile of clinical efficacy that was worth considering as a public health tool by the World Health Organization (WHO) and the European Medicines Agency (EMA).
The 4.5 years’ study results from a phase 3 double blind, randomised, placebo-controlled trial in children and adolescents aged 4 to 16 years showed that the administration of the quadrivalent dengue vaccine reduced the rate of dengue related hospitalisations by 84.1 per cent. This would definitely reduce the demand on our hospitals beds.
Both the reduction in the number of dengue cases and dengue related hospital admissions would further help to spare more Malaysians from the morbidity (illness) and mortality (deaths) associated with the disease syndrome.
Another aspect of the vaccine which is equally important is that no serious adverse events following immunisation (AEFI) were reported. In particular, there was no evidence of dengue disease enhancement and no increased risk of hospitalisation in Takeda’s Qdenga vaccine recipients.
This phenomenon called Antibody Dependent Enhancement (ADE) was seen with an earlier dengue vaccine and pre-vaccination screening was recommended; only persons with evidence of a past dengue infection would be vaccinated.
The WHO’s Strategic Advisory Group of Experts (SAGE) has endorsed the use of Takeda’s QDenga vaccine without pre-vaccination screening.
The performance of the dengue vaccine is best in populations with a high disease burden. Where the proportion of dengue positive people (seroprevalence) is in excess of 60%, the WHO has recommended countries to consider using the dengue vaccine.
In the Damansara Damai study, out of 85 respondents who agreed to participate in the dengue seroprevalence study, 74.1 per cent (n = 63) were positive for dengue IgG and 7.1 per cent (n = 6) were positive for dengue IgM.
A population-based cross-sectional study in the Petaling district, conducted from 18 August to 26 October 2018 with 533 participants, showed a seroprevalence of 79.0 per cent.
Depending on the population being studied, the seroprevalence of dengue in Malaysia varies from 28 to 94 per cent. And over 90 per cent of individuals above 60 years of age have been noted to be seropositive for dengue.
It may therefore be useful for the Ministry of Health (MOH) to pilot study the dengue vaccine in hotspots with a seroprevalence of more than 60 per cent prior to its consideration for the National Immunisation Program (NIP).
Except for Covid vaccines, most of the vaccines licensed by the DCA were first utilised in private health care settings prior to its incorporation into the NIP.
The Hepatitis B, Measles Mumps Rubella (MMR), Haemophilus influenza B, (HiB), Human Papilloma Virus (HPV) and Pneumococcal Conjugate Vaccines (PCV) were widely used by general practitioners and doctors in private clinics and hospitals before inclusion into the NIP in 1989, 2002, 2002, 2010 and 2019 respectively.
The Tetanus, Diphtheria, Pertussis (Tdap) vaccine in pregnant mothers and influenza vaccine in elder persons is now being seriously considered by the MOH.
I guess it will not be much different with the dengue vaccine. There will be selective usage in the MOH and wider utilisation in the private health care sector prior to its inclusion in the NIP.
Cost effective analysis will require to be undertaken to study the potential impact of the dengue vaccine on the cost and health outcomes of dengue fever.
The cost of dengue illness and vector control activities to prevent it was estimated at US$175.7 million a year in a 2015 study. Two think tanks have suggested that there is an opportunity to reduce the economic burden of dengue by 50 per cent if a previous dengue vaccine with an overall efficacy of 60 per cent was approved for use.
All recipients of the Takeda Qdenga vaccine are highly encouraged by their vaccinators to participate in an active surveillance study. With more extensive usage of the dengue vaccine, we would be able to pick up extremely rare AEFIs, which cannot be captured within the limited numbers of clinical trials.
This is a form of pharmacovigilance and post-marketing surveillance which would contribute invaluable information to the dengue real world experience.
Dr Musa Mohd Nordin is a consultant paediatrician.
- This is the personal opinion of the writer or publication and does not necessarily represent the views of CodeBlue.
