I think that your essay is not long enough but this short argument is leading you to the great essay. I would recommend you to write at first something about vaccinations and how it all started.
Then, you could write more about types of them and why some people are using them, and some people are against them. It is good to have some evidence that will support your arguments. In the end, I would recommend you to write your own opinion on vaccination and how are you feeling about that modern kind of medicine.