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WHO issues revised findings on Dengue Vaccine

By LaLaine M. Jimenea

FORMER HEALTH Secretary Janette L. Garin said she is “glad” that the World Health Organization (WHO) has issued a revised paper on the controver-sial Dengvaxia vaccine and “has clarified the true benefit of the dengue vaccine.”

In a statement, Garin said that “The DOH was correct all along that the dengue vaccine provides protection and is safe to adminis-ter to address the growing danger posed by dengue. We welcome the more in depth findings by the WHO on the safety and efficacy of the dengvaxia anti dengue vaccine.”

She added that, “We remain firm in our conviction that the vaccination program in regions 3, 4a, and NCR went through rigid guidelines enumerated by no less than the WHO and was followed by the DOH. Nonetheless, it is the avowed duty of the DOH as an institution to look after the health of the public. And we support and thank the present DOH leadership in performing its duty to monitor public health and provide the needed services.”

On the other hand, Health Undersecretary Dr. Herminigildo Valle said that “based on the Updated Q and A from WHO, ang sinasabi nito ay ‘yong risk ng severe dengue sa mga nabakunahan na ay more or less the same ng mga nagkaroon na ng dengue na hindi pa nabakunahan. It also reaffirms the benefits, outweighs the risk of severe dengue and hospitalizations among those vaccinated na may previous dengue and in places where dengue has seroprevalence of 85%.”

Valle added, “this means in areas where 85% of the population has been exposed to prior dengue infection. Those places where the mass vaccinations were given have a presumed 90% seroprevalence.”

In a new position paper published Dec. 22, 2017 explaining the efficacy and safety of the French-made dengue vaccine Dengvaxia, the WHO said on Friday said the vaccine actually reduces the risk of people being infected with the disease, but the best way to avoid dengue is still avoid being bitten with mosquitoes.

In a second revision of its paper “Updated Questions and Answers related to the dengue vaccine Dengvaxia® and its use,” WHO said the risk of people getting severe dengue after vaccination is actually the same as those who have been inoculated with Dengvaxia because of the high rate of dengue prevalence among Filipinos.

In its new paper, WHO reiterated its previous conf irmation that Dengvaxia had proven to be effective in reducing the risks of contracting dengue and hospitalization for dengue infection upon vaccination.

“The results confirmed previous findings that, overall, vaccinated trial participants had a reduced risk of virologically-conf irmed severe dengue and hospitalizations due to dengue,” WHO said.

“Trial participants who were inferred to be seropositive at the time of first vaccination had a durable protection against severe dengue and hospitalization during the entire 5-year observation period,” it added. WHO pointed out that “in the areas in the Philippines where Dengvaxia® was introduced (mainly through school programmes), the seroprevalence (or the rate of incidence of dengue infection) was estimated to be at least 85%.”

“A seroprevalence of 85% means that 85% of the population is seropositive and will benefit from Dengvaxia,” WHO said.

WHO also pointed out that the new analysis by Sanofi Pasteur of its clinical trial data suggested “a similar rate of severe and hospitalized dengue between unvaccinated seropositive persons and vaccinated seronegative persons.”

This meant the clinical possibility of a dengue-free person contracting severe dengue after vaccination with Dengvaxia is just the same as the clinical rate of a previously-infected person getting severe dengue after vaccination if he contracts dengue again. Based on findings on the disease, a person who contracts dengue is still vulnerable to the three other types of the dengue virus.

“The clinical severity in the vaccinated seronegative group was similar to that of severe cases in the unvaccinated seropositive group,” WHO said.

“There is no evidence that clinical manifestations of disease were more severe in vaccinated seronegative persons compared to unvaccinated seropositive persons. For the entire vaccinated population, overall, the risk of severe dengue is reduced compared to a non-vaccinated population,” it added.

All seropositive patients with severe dengue recovered WHO also highlighted the Sanofi Pasteur report that all seropositive patients inoculated with Dengvaxia and still contracted severe dengue, including dengue hemorrhagic fever, were able to recover from the disease. “In the clinical trials for those aged 9 years and above, the cases of severe dengue that occurred in initially seronegative vaccine recipients were categorized by the company as Dengue Hemorrhagic Fever Grades I and II and did not lead to shock, severe bleeding or death (12). All of the patients with dengue illnesses in the trial recovered,” WHO said. The organization said there were still no clear findings to explain why there is the possibility of seropositive persons contracting severe dengue, but limited its recommendation for vaccination to those nine years old and above.

“No long-term data beyond the trial observation period of 5 years currently exist. In the trial, the highest risk was in the third year and subsequently declined. Theoretically, based on the model that the vaccine acts like a silent primary infection, it is expected that the elevated risk of severe disease in vaccinated seronegative persons should disappear after they have had a natural infection,” it said.

WHO said the best way still to avoid being infected with dengue is to avoid being bitten by mosquitoes. “All individuals, regardless whether they have been vaccinated or not, should take personal protective measures to avoid mosquito bites. Furthermore, for any individual who presents with clinical symptoms compatible with dengue virus infection, regardless whether they have been vaccinated or not, prompt medical care should be sought to allow for proper evaluation, monitoring and clinical management. With proper medical care, severe dengue can be well managed.”

WHO issued the clarification after analysing the data submitted by Dengvaxia manufacturer Sanofi Pasteur on the results of its further examination of its earlier findings that there was big risk of people who have not had contracted dengue before contracting a severe case of dengue after being vaccinated with the Frenchmade vaccine.

The WHO findings come in the heels of concern that a nationwide vaccination program implemented in the last months of the Aquino Administration and continued by the DOH under President Rodrigo Duterte had exposed hundreds of thousands of Filipino children inoculated with Dengvaxia after Sanofi Pasteur announced the higher risk of severe dengue for seronegative patients.

The disclosure of the higher risk for the so-called seronegative people, or those who have not had dengue before vaccination, triggered a furor in the Philippines that led the Department of Health to suspend its distribution and the Senate to summon former President Benigno S. Aquino III, Garin and former officials of his Administration to explain the procurement of the vaccines and the nationwide vaccination program.

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