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Vaccinating against Dengue Fever likely to increase Zika outbreaks, warn Researchers

Dengue and Zika are both part of the Flaviviridae family transmitted through a common mosquito host

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Toronto, Nov 1, 2016: Vaccinating against dengue fever could increase outbreaks of Zika, warns a study by a team of researchers from Canada and China.

As dengue and Zika are both part of the Flaviviridae family transmitted through a common mosquito host, the researchers wanted to know how vaccinating for one would affect the incidence of the other.

“Vaccinating against one virus could not only affect the control of another virus, it could in fact make it easier for the other to spread,” said one of the researchers Jianhong Wu, Professor at York University in Toronto, Canada.

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The research, published in the journal Scientific Reports, identifies a potentially serious public health concern.

More than a third of the world’s population lives in areas where dengue is endemic and cases of co-infection with Zika have already been reported, according to the study.

“Recent evidence suggests that dengue virus antibodies can enhance the Zika virus infection. For that reason, we developed a new math model to investigate the effect of dengue vaccination on Zika outbreaks,” Wu said.

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The team’s model showed that vaccinations for dengue increase the number of people contracting Zika.

It also showed that the more people in a particular population that are vaccinated against dengue, the earlier and larger the Zika outbreak.

The research also found that the most effective way to minimise the unintended effect of dengue vaccinations on Zika outbreaks is through an integrated strategy that includes mosquito control.

“We concluded that vaccination against dengue among humans can significantly boost Zika transmission among the population and hence call for further study on integrated control measures on controlling dengue and Zika outbreak,” Yanni Xiao, Professor at Xi’an Jiaotong University in China, said.

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The researchers noted that their findings do not discourage the development and promotion of dengue vaccine products, however, more work needs to be done to understand how to optimise dengue vaccination programmes and minimise the risk of Zika outbreaks.

Although vaccines for dengue have been developed and are in use, there is currently no vaccine for Zika. (IANS)

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Dengue Vaccine Should Not Be Used Widely: UN Health Agency

UN Health Agency issued an important statement regarding the dengue vaccine

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Dengue vaccine.
A Manila Health officer shows off a pair of vials of the anti-dengue vaccine Dengvaxia after being recalled from local government health centers Tuesday, Dec. 5, 2017 in Manila, Philippines. The World Health Organization says the first-ever vaccine for dengue needs to be dealt with in "a much safer way," meaning that the shot should mostly be given to people who have previously been infected with the disease. VOA

The World Health Organization says the first-ever vaccine for dengue needs to be dealt with in “a much safer way,” meaning that the shot should mostly be given to people who have previously been infected with the disease.

In November, the vaccine’s manufacturer, Sanofi Pasteur, said people who had never been sickened by dengue before were at risk of developing a more serious disease after getting the shot.

After a two-day meeting this week, WHO’s independent vaccines group said it now had proof the vaccine should only be used “exclusively or almost exclusively in people who have already been infected with dengue.”

Also Read: Anti-dengue Antibody Drug May Neutralize Zika Virus

The U.N. health agency said a test should be developed so doctors would be able to quickly tell if people had previously been sickened by dengue – but the group acknowledged doing that so isn’t straightforward.

“We see significant obstacles in using the vaccine this way, but we are confident this also spurs the development of a rapid diagnostic test,” said Dr. Joachim Hombach, executive secretary of WHO’s expert group, during a news conference Thursday.

Representational image for dengue vaccination
Representational image. Wikimedia Commons

Sanofi said last year that doctors should consider whether people might have been previously infected with dengue before deciding whether they should risk getting immunized. The company said it expected to take a 100 million euro ($118 million) loss based on that news.

People who catch dengue more than once can be at risk of a hemorrhagic version of the disease. The mosquito-spread virus is found in tropical and sub-tropical climates across Latin and South America, Asia, Africa and elsewhere. It causes a flu-like disease that can cause joint pain, nausea, vomiting and a rash. In severe cases, dengue can result in breathing problems, hemorrhaging and organ failure.

About half the world’s population is at risk of dengue; WHO estimates that about 96 million people are sickened by the viral infection every year.

Also Read: Dengue fever may increase risk of stroke: Study

Following Sanofi’s announcement last year, the Philippines halted its dengue immunization program, the world’s first national vaccination program for dengue. The government also demanded a refund of more than 3 billion pesos ($59 million) from Sanofi and is considering further legal action.

In February, the Philippines said the vaccine was potentially linked to the deaths of three people: all of them died of dengue despite having received the vaccine.

The country imposed a symbolic fine of $2,000 on Sanofi and suspended the vaccine’s approval, charging that the drugmaker broke rules on how the shot was registered and marketed.

More than 730,000 children aged 9 and above in the Philippines have received at least one dose of the dengue vaccine, usually delivered in three doses.

There is no specific treatment for dengue and there are no other licensed vaccines on the market.  VOA