The only approved vaccine for dengue may actually increase the incidence of dengue infections requiring hospitalization rather than preventing the disease if health officials aren’t careful about where they vaccinate, new public health research published September 2 in Science suggests.
Dengue typically causes a mild first infection but a far worse one if someone is infected with the virus a second time. There are four types of dengue virus, and it is thought that the body’s response to the first infection leads to more severe disease upon a second infection. This has long posed challenges to scientists developing a vaccine, who worried that any candidate that failed to protect fully could raise the risk of making people sick rather than keeping them well.
In their new study, researchers from the Johns Hopkins Bloomberg School of Public Health, Imperial College London and the University of Florida re-analyzed data from vaccine trials conducted in 10 countries with more than 30,000 participants as well as recently published data on the long-term follow-up of these participants. Using that data, they developed mathematical models to understand how a vaccine rollout would affect people in countries where transmission of the disease is high, moderate or low. They found that while the vaccine can reduce illness and hospitalization by 20 to 30 percent in places where there is high transmission of dengue, it may actually significantly increase illness and hospitalization if used in locations where there is lower transmission of the virus.