That which is legislated is the avoidance of what is apparent [of these harms] and to take caution to the extent that is related in the Sharīʿah.

The servant is ordered to take caution against the apparent causes of evil and to avoid them to the extent that is related in the Sharīʿah.

That which is correct in our view is what is authentically reported from him [sas] that he said: “There is no contagion” and that nothing will afflict a soul except what has been written for it.

[Go ahead], flee from the leper as you would flee from a lion, (for its meaning) is that there is no contagion, he will not pass [his leprosy] to you...

His saying: “There is no contagion”, he means by it that nothing transmits [what it has] to anything else such that harm comes from its direction.

They used to believe that when the sick person mingled with the healthy, he would make them become sick and pass his disease to them. Likewise [did they believe] regarding camels. So the Prophet [sas] negated that and falsified it.

However, it is not the case that a healthy person, merely by mixing with a person who has a transmissible disease, that this disease will necessarily transmit to this healthy person.

When a man suffers from what is called “influenza”—this being an illness despite which a man is still able to leave his house, though it is a “contagious illness” as the doctors say—would it be permitted for this man to pray in his house...

The great scholar of Prophetic traditions, Shaykh al-Albānī [rh] in the context of contagion outlined a number of conditions for taking precaution that keep it within prescribed limits and bounds.

What is the ruling on what is called vaccination (taṭʿīm or talqīḥ) which is given to children so that they are not afflicted with specific diseases.