Bill Gates listed vaccines as one of the means in which population would be controlled. I don't know why he would list them that way unless they reduce fertility or cause early mortality in some cases. I don't think a good vaccine like what used to be around (which always had some level of risk/injury but in general were good things) was intended for population control but to protect life. After I heard him say that I became very wary of modern vaccines.
I came across this in trying to research past discussions about bill Gates and chemtrails. This comment of his is taken out of context and distorted by antivaxxers trying to push an agenda. He mentioned vaccines in the context of population size because it is understood that when you vaccinate third world and African countries, as they no longer lose a high proportion of children to death from childhood/early life illnesses, they have fewer kids. There is data showing that high birthrates are combating the loss of children and when this risk is eliminated, people choose to have fewer kids.
For people obsessed about overpopulation, vaccines, by eliminating serious illnesses that no longer kill children in the industrialized world in significant numbers, but still impact the third world, are seen as a harmless tool that will naturally put the brakes on population growth.
It is abundantly clear that this is what he was talking about in that oft quoted snippet. And it's well understood that people don't try to have as many children in an environment of fewer children dying.
Vaccines are developed by companies to prevent illness and death, they have to demonstrate the ability to do so in clinical trials and to demonstrate safety or else they will not be used or paid for. Bill Gates has no say in how these products turn out. He is not an inventor of pharmaceuticals or vaccines. He's a rich guy with funding capacity. Companies are incentivized to make money, not pursue Gates' fantasies.