Dengue, a mosquito-borne disease, affects millions of people every year across Asia, Africa and Latin America. And it’s expanding geographically as warmer temperatures and urban growth allow mosquito populations to thrive in new regions.
At first glance, dengue seems like an obvious candidate for vaccination. It is caused by a virus. Infection triggers an immune response. Vaccines against similar viruses already exist.
But dengue is complicated. It is not caused by just one virus, but by four closely related ones known as serotypes. When someone is infected with one, the immune system usually protects them against that specific type – but not against the other three. In some cases, a previous infection can actually make a new infection happen more easily.
