Question Summary:
Aside from dua does the shariah allow for us to use haraam substances to prevent future occurrences?

Question Detail:

It is understood that haram and impure substances can be used in case of need and necessity. Our question is in the case of the polio vaccine as well as other vaccines the vaccine is given when the patient doesn’t have the sickness. So the doctrine of necessity doesn’t come into play. We are told that this will prevent a future attack of the virus which may or may not come. Now we know Allah brings the sickness and the cure and if it is decreed that a person will get the sickness no drug can stop it. Caution is advised but does caution include the taking of haram and najis ingredients? We read in hadith: that the Messenger of Allaah sallallaahu 'alayhi wa sallam said, "Caution is of no avail against the decree but supplication benefits those things that have occurred and have not yet occurred. For indeed while the tribulation is descending the supplication meets it and they remain struggling with one another until the Day of Judgement."
So aside from dua does the shariah allow for us to use haraam substances to prevent  future occurrences?
 

Answer :

In the name of Allah, Most Gracious, Most Merciful
Assalaamu `alaykum waRahmatullahi Wabarakatoh
If medical experts regard taking polio vaccine to be necessary to prevent future occurrences, it will be permissible. The doctrine of necessity is not confined to the past or present. It includes the future as well. A person has sufficient food for the day but regards working for tomorrow to be necessary.
And Allah knows best
Wassalam
Mufti Ebrahim Desai
Darul Iftaa, Madrassah In'aamiyyah