As a vaccine safety controversy continues to play out in the Philippines, WHO advisers have updated their recommendations for Sanofi's Dengvaxia. The experts said it should be administered after a test confirms recipients have had a prior infection.
Alejandro Cravioto, the chair of the WHO's Strategic Advisory Group of Experts on Immunization, told reporters on a conference call that the vaccine "needs to be dealt with in a much safer way by using it exclusively or almost exclusively" in people who have had a confirmed prior infection.
The problem? A point-of-care test for dengue doesn't exist yet. According to Reuters, Sanofi Pasteur head David Loew said the company is working with potential partners to develop a test but it'll take two years or more to be ready.
In making its recommendation, WHO said countries should consider the accuracy of available tests, dengue epidemiology, costs and hospitalization rates to plan their dengue strategies.
Sanofi responded that the "recommendation confirms the public health value of Dengvaxia and its potential to reduce the overall burden of dengue in high endemic populations." The company reiterated its commitment to developing a rapid diagnostic test.
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The Dengvaxia safety issue cropped up late last year, when Sanofi said an updated trial data analysis had shown an increased risk of severe dengue cases in Dengvaxia recipients who hadn't been exposed to the virus before. That's because the shot can act as a natural first infection, and second dengue infections can be much more serious, according to a 2016 study published in Science.
The disclosure swiftly triggered an uproar in the Philippines, which was in the midst of a mass vaccination campaign. Officials there stopped all vaccinations, demanded a refund and started an investigation. In February, a preliminary report from the Philippine General Hospital said investigators found a "causal association" between three deaths and the vaccine. Sanofi responded that "no deaths related to the vaccine have been reported to us."
Along the way, the company has pledged to continue to cooperate with authorities and maintained its vaccine can help lessen the burden of dengue.
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Sanofi spent 20 years and $1.5 billion developing Dengvaxia, but so far the vaccine has been a commercial disappointment. Dengvaxia generated only €3 million in sales last year—a 98% decrease from 2016—after Sanofi refunded unused doses in the Philippines. Issues with the vaccine cost the company €158 million in the fourth quarter, CFO Jérôme Contamine said on a conference call.
Meanwhile, Takeda and a team of the NIH and Brazil's Butantan Institute are working on their own late-stage dengue vaccine programs.