Eleven countries have approved the sale of Sanofi’s dengue vaccine. For its part, the World Health Organization convened a Strategic Advisory Group of Experts which reviewed the evidence and recommended that countries consider introduction of the vaccine only in settings with high endemicity, defined by a seroprevalence of at least 70 percent in the target age group. The experts advised not to use the vaccine in populations with seroprevalence less than 50 percent.
The International Federation of Red Cross and Red Crescent Societies in the Philippines was supportive of the rollout. Dr. Bhanu Pratap, health coordinator, called the introduction of the vaccine “a positive move, especially for those living in the worst affected areas and for children,” pointing out the Philippine Red Cross provides 53 percent of the country’s blood supply, and that some dengue sufferers require blood platelet transfusions.
However, the vaccine proved expensive, and the three doses required presented a burden for governments to commit to roll it out. This explains why Mexico, for example, approved sales of the vaccine to the private sector first, planning a public sector rollout only later on.
Two countries that did roll out the dengue vaccine on a large scale have reacted differently to Sanofi’s announcement that the vaccine should be administered only to those previously exposed to dengue.
In the Philippines, it’s been administered to kids in Metro Manila, central Luzon and Calabarzon, where some of the highest levels of dengue infection had taken place in the past (the goal of the Department of Health was to reduce dengue cases by 24 percent). The number of children who received initial doses of the vaccine is said to total 700,000 of which 70,000 fall in to the category of not having been exposed to dengue before, and who will thus run the risk of a possibly “severe” case if infected later on. Health Secretary Francisco Duque III, who is generally considered a sober man, said that children who have and have not been exposed to dengue prior to receiving the vaccine are protected for a 30-month period: “It is after this period that an infection could be dangerous. Immunized children with no history of dengue infection who are exposed to the dengue virus after the two-and-a-half-year protection gap are in danger of possible severe disease.” Sanofi’s definition of “severe,” which is not the same as the layman’s, means symptoms including two days of fever, a lower platelet count and bruising. This also seems to be the DOH’s definition.
In contrast to the Philippines, Michele Caputo Neto, health secretary of the Paraná State of Brazil (which has a federal system), announced on Nov. 30 that despite the Sanofi announcement, it would continue administering the vaccine. Neto pointed out two things:
First, scientific evidence submitted by Sanofi clearly demonstrated that the vaccine does not cause dengue, only the bite of the infected mosquito is capable of transmitting the disease. This new study pointed out that there is a 0.5 percent higher risk for a vaccinated individual not previously exposed to the virus develop dengue with alarm signals than an unvaccinated individual who has never been exposed. In addition, all identified cases of adverse events had full recovery, with routine treatment.
Second, Neto stated that this “reinforces the strategy adopted by the state, which offered the vaccine only in the 30 municipalities that concentrated 82 percent of the [dengue] cases registered […], 91 percent of severe cases and 87 percent of dengue deaths.” These are the cities that have faced consecutive epidemics, with high viral circulation and recorded a large number of cases. Paraná has administered the vaccine to 300,000 people. For the vaccine to result in lasting immunity, three doses are required, given six months apart.
Paraná pointed to statistics backing up their decision to continue using the vaccine. According to Julia Cordellini, superintendent of health surveillance, between August 2015 and July 2016, Paraná registered 56,351 cases and 63 deaths from dengue.
“Since August 2016, when the vaccination campaign was defined, 1,061 cases of dengue fever in Paraná and no deaths from the disease were confirmed, and only 40 people vaccinated were notified with mild dengue without laboratory confirmation, only clinical suspicion. That represents 0.01 percent of the total vaccinated.”