AsianScientist (Dec. 6, 2017) – Philippine health authorities have suspended the sale and distribution of Dengvaxia, the world’s first dengue vaccine, following the release of a report raising concerns about the vaccine’s safety in individuals who have never been infected with dengue.
The new findings, announced by vaccine maker Sanofi Pasteur on November 29, confirmed that Dengvaxia provides a “persistent protective benefit” for those who have previously been infected with dengue. In people who have never had dengue, however, vaccination could lead to more cases of severe disease upon a subsequent natural infection with the virus, said the report.
While a first infection with one of the four dengue virus serotypes is typically mild, a second infection with a different serotype can cause severe disease; it is thought that the body’s immune response to the first infection enhances the second.
The Sanofi report adds to previous clinical trial data indicating that the vaccine was associated with an increased risk of hospitalization for children under the age of nine. According to a 2016 study published in Science, one possible reason for this outcome is that the vaccine mimics a first infection in individuals who have never been exposed to dengue, thus setting them up for more severe disease upon a subsequent natural infection.
The symptoms of severe dengue include fever lasting for at least two days, low platelet count, bruising and severe bleeding. Severe dengue is among the leading causes of death in many Southeast Asian and Latin American countries.
However, Dr. Ng Su-Peing, Sanofi’s global medical head, said during a press conference on December 4 that vaccine-related severe dengue cases would be relatively rare.
“To see even one additional severe dengue case among those who have never seen a dengue infection before, you would need to vaccinate 5,000 people where nine out of ten have seen infection before and one out of ten hasn’t.”
“The overall benefit of vaccination in a highly endemic setting such as what we have here in the Philippines is still in line with the World Health Organization (WHO) recommendation for vaccination introduction,” she said.
However, Ng does not recommend the vaccine for those who have never been infected with dengue virus. The WHO, for its part, has advised that, pending a full study on its safety and efficacy, the vaccine should only be rolled out in populations with a high prevalence of dengue infection.
“You have to look at the local data, local epidemiology, the burden of the disease in the country, what proportion of the population in a given country have had previous dengue. From the government data in the Philippines, at least nine out of ten children, by the time they reach adolescence, have had dengue,” said Ng.
She added that dengue infection can be difficult to discern, as the majority of infected individuals show no symptoms.
The press conference came after the Philippine Department of Health (DOH) announced that it would put on hold its dengue immunization program until “experts are able to review new developments on the Dengvaxia dengue vaccine.”
In a separate press conference, DOH spokesperson Dr. Lyndon Lee-Suy assured the public that the government would continue to monitor vaccinated children. A series of consultation meetings is scheduled this week between the Philippine government and Sanofi Pasteur to discuss the next steps. Lee-Suy said that the WHO’s Strategic Advisory Group of Experts is also set to meet within the week to study the Sanofi report.
Since 2016, more than 700,000 Filipino children have received Dengvaxia for free under the DOH’s school-based immunization program, after the vaccine was licensed by the Philippine Food and Drug Administration.
Source: Sanofi Pasteur; Photo: Shutterstock.
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