What method should be used to prove that a particular vaccine protects the body against a specific infectious disease?

The experimental method in biology allows you to actively study a particular phenomenon. Any experiment is associated with observation, but experiment and observation are not identical. In contrast to the description and comparison, the basis of which is observation, the experiment allows us to study not only what catches the eye and is immediately visible to the experimenter, but also what is hidden in the depths of the subject, phenomenon. The experiment allows us to study phenomena purposefully, under conditions that can be accurately taken into account qualitatively and quantitatively, as well as recreate again.

Remember: The process of learning a person lasts a lifetime. The value of the same knowledge for different people may be different, it is determined by their individual characteristics and needs. Therefore, knowledge is always needed at any age and position.