Question Summary:
s it permissible in general to inject medicine which is derived from najis into a healthy human being ?

Question Detail:

i would like  to know the following:
in checking the ingredients of the  polio vaccine we find the following ingredients:
phenoxethanol, formaldehyde, calf serum, and monkey kidneys.
this information was gathered from a website, and assuming that it is  true, then is it permissible to use this vaccine?
and is it permissible in general to inject medicine which is derived from najis into a healthy human being while the person is not suffering from any disease?

Answer :

In the name of Allah, Most Gracious, Most Merciful
Assalaamu `alaykum waRahmatullahi Wabarakatoh
In principle, the Fuqaha have ruled that one will be execused from taking medication having haram and impure substances in the case of need and necessity based on the principle necessity relaxes prohibition. This is a medical issue and it is only appropriate that medical experts determine the need and necessity. If medical experts advise that there is a need to inject haram vaccine against some sickness and one abides by that, he will be excused and not sinful. Medical experts’ differences on this as well as whether one should take such vaccines or not is a different issue.
And Allah knows best
Wassalam
Mufti Ebrahim Desai
Darul Iftaa, Madrassah In'aamiyyah