You are most welcome. As taxpayers, you all footed the bill for me to get a PhD; this is how I pay you back for my wonderful education!
Sanofi has been pushing hard to get its vaccine licensed. Of course, their motives in doing so contain some element of opportunism, since the spread of dengue into the US and Europe creates a level of concern about dengue that did not previously exist. (Diseases that only affect people in distant third world countries receive scant attention and thus very little research funding.)
However, Sanofi is not the only company to develop a vaccine. Takeda, a Japanese company, also has a vaccine candidate which they are also testing in phase 3 trials. The US government (specifically, the NIH and the Army) has developed a couple of vaccine candidates which are being tested in collaboration with Merck and GSK. There are probably others at all stages of development.
Every single one of these vaccines has the same issues that the Sanofi vaccine has, which is that there is a risk of the vaccine causing unequal levels of immunity against dengue. In turn, this could cause the patient to be *more* susceptible to very serious and potentially life-threatening disease if they catch one of the strains that they did not become sufficiently immune to.
Please note that the increased susceptibility of a patient to severe disease from catching a second strain of dengue is well documented in the medical literature. The hypothesis that this dynamic might operate in vaccinated patients is just that, a hypothesis—but is a concern that any developer of dengue vaccine must answer before the FDA (or foreign regulators) will approve the vaccine for market.
In reports that I have read, the vaccines have not induced equal levels of immunity against all four strains; typically, fewer than half of the study participants become sufficiently immune to at least one strain. So the pharmaceutical companies have some work to do to secure that FDA approval.