And the world has spent a lot of money on it: The GAVI and the Gates Foundations are each pledging a lot of money towards it, and developing countries themselves have been doing a lot of effort.
世界花了很多钱在免疫上 国际免疫预防联合会和盖茨基金会 都在免疫上投入很多钱 发展国家自身也做了很多努力