Vaccination is not a 100% guard against infection, but it has a substantial success rate. However some individuals cannot be immunised, such as the child linke

Vaccination is not a 100% guard against infection, but it has a substantial success rate. However some individuals cannot be immunised, such as the child linked in the article who could not be immunised due to a weak immune system. Also, children under the minimum age to be safely vaccinated rely on herd immunity to stay safe. Having everyone in the community vaccinated makes it much less likely that these infections will spread from outside and put the weaker members of the community at risk.