Medical Perspectives | Infectious Diseases

February 26, 2020



Dr. Michael Miranda, M.D.

Dengue is fast emerging pandemic-prone viral disease in many parts of the world which flourishes in urban poor areas, suburbs and the countryside but also affects more affluent neighbourhoods in subtropical and tropical countries like the Philippines.  It is a mosquito-borne viral infection causing a severe flu-like illness and, sometimes causing a potentially lethal complication called severe dengue. According to DOH Dengue Disease Surveillance Report, a total of 117,654 dengue cases were reported nationwide from January 1 to November 4, 2017, with a Case Fatality Rate of 0.54% (657 cases) with the highest age group being in 5-9 years old.  

With the increasing number of cases and fatality brought about by this disease, the previous Administration found a solution that might help control this rising epidemic. Back in December 22, 2015, the Philippines became the first Asia country to approve the sale of the world’s first ever dengue vaccine “Dengvaxia”, manufactured by a French pharmaceutical company, Sanofi Pasteur. Eventually, then Health Secretary Dr. Janette Garin said that the DOH would be willing to purchase the said vaccine, spending about Php 3 billion. DOH clarified that the vaccine is only recommended for people ages 9-45 years old. With the vaccine now available in the country, DOH started a Mass vaccination program on April 4, 2016 and began injecting the first batch of school children from Central Luzon, Metro Manila and Southern Tagalog Region. 

According to the WHO Scientific Advisory Group of Experts on immunization, countries with dengue seroprevalence of ≥70% should be targeted for vaccination. Philippine Society for Microbiology and Infectious Disease (PSMID) subsequently released a position statement and noted safety signals in the clinical trials suggesting a potential risk of antibody-dependent enhancement (ADE) of breakthrough dengue infection when the vaccine is administered to seronegative individuals, which can mimic a first infection in seronegative children (those with no previous infection), and eventually a natural infection later in life could lead to severe disease. The possibility that dengue vaccines can cause severe dengue through ADE has led to serious concern regarding the safety of mass vaccination programs. PSMID thus recommended additional studies, including long-term surveillance of vaccinated individuals, to validate this observation. On November 29, 2017, Sanofi Pasteur released news of additional safety and efficacy analyses of five years of clinical data on study participants in the vaccine trials in Asia and Latin America. It stated continued protection against dengue among those who had prior dengue infection but recommended against vaccination of those without previous infection and only to be restricted to those with prior exposure to dengue.  

In response to the recent findings and statements, On May 9, 2017, the Food and Drug Administration of the Philippines (FDA) ordered a halt on the distribution, promotion and advertisement of the dengue vaccine. DOH also stated last December 1, 2017 that it will suspend the mass dengue vaccination program in conjunction the announcement of Sanofi Pasteur about the possible risks brought about by Dengvaxia and of the number, 10% (70,000 people) who had no prior infection, were reportedly at risk of contracting the worse symptoms of dengue. 

 

Sanofi Pasteur admitted that Dengvaxia may be harmful when administered to individuals not previously infected with dengue. This lead to a public uproar and a large scale safety concern with regards to all those school children that was vaccinated with Dengvaxia. To this date, about 733,713 children from the said regions are currently vaccinated. The current government is trying to probe and resolve the issue on who’s to blame and be accountable in this disarray.

 

In the recent statement of PSMID, they assure the public that Dengue vaccine is safe and effective among those with prior exposure to dengue. Current evidence does not support giving dengue vaccine to individuals without past dengue infection. Moreover, for individuals who have yet to complete the 3 doses, they are encouraged to wait for further advisory from the Department of Health, about the long-term efficacy of the vaccine and for those who intend to get vaccinated, a history of past dengue infection should be determined. Risks and benefits should be discussed prior to vaccination, as well as the risks of not being immunized. Vector control such as clearing of stagnant waters that might be a breeding ground for mosquitoes, fumigation, insect repellents and basic hygiene is still advised thus preventing dissemination and transmission of dengue.

 

In conclusion, there is still no simple solution in resolving the epidemic of dengue in our country. A viable, promising and potentially effective vaccine was introduced however, it was prematurely employed without further post-marketing surveillance. What’s worse, it was embedded in a lot of controversy from its procurement and utilizations and is allegedly used as a tool for corruption for some government officials with the effects only now being recognized by the public. With the growing safety concern and worry from the public especially the parents of all those school children that were vaccinated, the only thing that can be advised to them is too keep a close watch, be mindful, and vigilant of the possible symptoms that can manifest on their children in order to prevent any untoward demise.

 

References:

  • WHO. (2009). Dengue: Guidelines for diagnosis, treatment, prevention and control.
  • Dans ALDans LFLansang MADSilvestre MAAGuyatt GH. Review of a licensed dengue vaccine: Inappropriate subgroup analyses and selective reporting may cause harm in mass vaccination programs. J Clin Epidemiol.(2017 Nov 24)
  • Halstead SB. Dengvaxia sensitizes seronegatives to vaccine enhanced disease regardless of age. Vaccine. (2017 Nov 7)
  • Flasche SJit M, Rodríguez-Barraquer I, et al. The Long-Term Safety, Public Health Impact, and Cost-Effectiveness of Routine Vaccination with a Recombinant, Live-Attenuated Dengue Vaccine (Dengvaxia): A Model Comparison Study. PLoS Med. 2016 Nov 29;13(11)
  • Philippine Society for Microbiology and Infectious Disease. PSMID Interim Guide on the Use of Dengue Vaccine. (Update, 6 December 2017) Accessed at .
  • Philippine Society of Microbiology and Infectious Diseases. PSMID Statement on Dengue Vaccination in Adults. (25 October 2016) Accessed at .
  • Sanofi. Sanofi updates information on dengue vaccine. 29 November 2017. Accessed at .
  • Merez A, Ramos P. TIMELINE: The Philippines' dengue vaccine program. 8 December 2017 Accessed at < http://news.abs-cbn.com/focus/multimedia/slideshow/12/08/17/timeline-the-philippines-dengue-vaccine-program>
  • Hadinegoro SR, Arredondo-Garcia JL, Capeding MR, et al. "Efficacy and long-term safety of a dengue vaccine inregions of endemic disease." N Engl J Med (2015): 1195-1206.
  • World Health Organization. Background paper on Dengue Vaccines prepared by SAGE working group on Dengue vaccines and WHO secretariat. Geneva, 17 March 2016. Accessed at: http://www.who.int/immunizatio...

Accessed at <http://www.who.int/denguecontrol/disease/en/>

 

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