Vaccinations against dengue should only be given following a diagnostic test to determine that the patient has been exposed to the disease, according to recommendations from the World Health Organization (WHO).
The update follows the interim recommendations by the WHO's Strategic Advisory Group of Experts (SAGE) that the vaccine should not be used in people without prior exposure to dengue, and that point-of-care testing should be done prior to vaccination.
SAGE, the WHO's top advisory body on immunization, shared the results from their spring meeting, which addressed not only the dengue vaccine, but also the RTS,S malaria vaccine, and general vaccination programs concerning measles and rubella and polio.
But dengue was top of mind, given the recent controversies surrounding the dengue vaccine Dengvaxia (Sanofi Pasteur) in the Philippines. Questions had been raised about the safety and efficacy of Dengvaxia, particularly the increased risk of hospitalization among children younger than age 9. This was before the Department of Health in the Philippines late last year, and an investigation was launched into the effects of the vaccine.
In a press briefing, the SAGE group said they were able to review "new evidence" to complement their 2016 recommendations, and see how the data had changed. WHO researchers added that they were "fully aware" of the situation in the Philippines, and have been advising their regional offices and were monitoring the situation, as well as being in close contact with the authorities.
"We now have clear information that the vaccine needs to be dealt with in a much safer way by using it exclusively or almost exclusively in people who have already been infected with dengue before," Alejandro Cravioto, MD, chair of the SAGE on Immunization said. "We feel that a system will be developed that will make it easier to determine whether a person has been infected or not with dengue."
Joachim Hombach, MD, SAGE's executive secretary, added that while it may be a "significant obstacle" that they currently do not have a point-of-care test that gives information about past infection with the dengue virus, the advisory group felt that this "will spur the rapid development of a rapid diagnostic test."
In keeping with the WHO's 2016 , the vaccine against dengue may be given in countries where the endemicity is as high as 70%, but preferably 80%, though a point-of-care test should be done prior to vaccination as well.
WHO researchers said that independent mathematical modeling studies also proved that the dengue vaccine could see population benefits if it is a population with a seroprevalence over 80%, because in that situation, the number of people who had no exposure to dengue would be "very few."
Other Updates
In addition to the dengue vaccine, the SAGE group also addressed the malaria vaccine, RTS,S. The group said that they were reviewing the design of new pilot studies that would look into safety issues of the vaccine and how it could be delivered in a four-dose schedule. Once they have that information, WHO researchers said, they will be able to make a more specific recommendation about the vaccine.
They estimated that the pilot studies will take about 3 to 4 years to complete, so a decision may not be made until 2022.
At the meeting, SAGE also discussed the ongoing measles and rubella outbreaks in Venezuela and Brazil, which could put measles elimination in South America "in danger."
"Strengthening immunization in all countries with cases [of these diseases] will enable us to have better control of these two diseases in the future," Cravioto said.
The group also looked ahead to the potential end of polio, and said they hoped to have a real idea soon about how long it will take to get rid of the disease, as "the last mile is taking longer than we expected."