These trials will give a better idea of the number of doses required for a person to be immunized, as well as of the quantity on active principle (antigen) needed in each vaccine dose.
If a helper cell recognises an antigen, it becomes activated.
如果某一个助细胞识别出一个抗原，该助细胞就会被活化。
3
Some pandemic vaccines contain an adjuvant to reduce the amount of virus antigen to be used (an antigen is a substance capable of stimulating an immune response).