the vaccine doesnt contain fetal cells, in the case you are providing the vaccine is an attenuated virus approach.
the cells are used to manufacture quantities of the virus in an extremely weakened form. This gives a chance for the immune systemto mount a response before the pathogen initiates systemic disease response.
the cells in question are not freshly harvested from a foetus, the progenitor cells are harvested and kept in continual culture for use. the reason immortalized cells are used is to escape the "expiry date" of a normal cell.
>>Some vaccines currently available were developed using cell strains cultured from two fetuses aborted for other purposes in the 1960s.[6]<<
Which one? I don't remember any vaccine that injects immortalized cells.