those are muslim extremists or black afriacan racists or potentially future chinese and indian racists/expansionsits that want to "zerg" their enemies other civilisations or what they think of what is the "other"
because they think that vaccination slows down the human population growth, so the african nature and social infrastructure have at least a chance of being sufficient
What I find ironic is that this anti-vacc movement started in America. From what we know about North America's history, one reason Europeans managed to settle it fairly easily was when they arrived, the larger native settlements has already been depopulated by a more recent contact that has spread diseases. In Central and South America, the disease came right with the conquistadores.