What is the ruling on a man working as a medical assistant, giving injections to women who cannot find a woman to do so, or do not trust their experience, or are shy about him entering their homes, or have been previously harmed?

It is not permissible for women to be treated by a man if they can be treated by a woman. It is also not permissible for women to administer injections to other women if other women are able to do so. If it is not clear whether the woman has a valid excuse, there is no need to ask, and it is permissible to treat her, while observing the Sharia guidelines, such as avoidingKhalwa (private seclusion) and ensuring there is no fear of Fitna (temptation or discord).