When someone is vaccinated, they are very likely to be protected against the targeted disease.
9902
但是不是每个人都能接种疫苗。
But not everyone can be vaccinated.
9903
患有削弱免疫系统的基础病症（如癌症或艾滋病）或对某些疫苗成分严重过敏的人可能无法接种某些疫苗。
People with underlying health conditions that weaken their immune systems (such as cancer or HIV) or who have severe allergies to some vaccine components may not be able to get vaccinated with certain vaccines.
9904
但如果这些人生活在接种过疫苗的人群中，他们仍然可以得到保护。
These people can still be protected if they live in and amongst others who are vaccinated.
9905
如果社区中许多人都接种了疫苗，病原体便很难传播，因为它遇到的大多数人都具有免疫力。
When a lot of people in a community are vaccinated the pathogen has a hard time circulating because most of the people it encounters are immune.
9906
因此，接种疫苗的人数越多，无法接种疫苗的人接触有害病原体的可能性就越小。
So the more that others are vaccinated, the less likely people who are unable to be protected by vaccines are at risk of even being exposed to the harmful pathogens.
9907
这就是所谓的群体免疫。
This is called herd immunity.
9908
这对于那些不仅不能接种疫苗，而且很容易感染疫苗可预防疾病的人来说尤其重要。
This is especially important for those people who not only can’t be vaccinated but may be more susceptible to the diseases we vaccinate against.
9909
没有一种疫苗能提供100%的保护，群体免疫也不能为那些不能安全接种疫苗的人提供充分保护。
No single vaccine provides 100% protection, and herd immunity does not provide full protection to those who cannot safely be vaccinated.
9910
但是通过群体免疫，这些人将因其周围的人获得免疫接种而得到相当大的保护。
But with herd immunity, these people will have substantial protection, thanks to those around them being vaccinated.