Respuesta :
Hi !
In order for vaccines to protect a population from a pathogen:
A. Most of the population must be vaccinated
The answer is A! It’s called herd immunisation (like a herd of sheep, a herd of immunised people). Because some people may have weaker immune systems so they can’t have the vaccine and so they are relying on other people to be vaccined and not catch the virus to pass it onto them.