Somebody who is a baal teshuva and studying with Lev L'Achim asked a question about his parents who are still not religious. He explained that his father has wanted to get vaccinated against Corona urgently and needs his son's assistance to bring him to get the vaccination. He eventually realized that his father is so desperate for the vaccine because until the pandemic he would go every Shabbos to the beach and go fishing, an activity he loved and brought him peace and calmness. When the pandemic hit he could no longer go and do this on Shabbos - he just stayed home the entire time. But now there are vaccines  and if he gets the shot he can go back to his beloved fishing. And he wants his son to help go get the vaccine so he can get back to fishing.

Now, I do not understand why he needs his son to take him to get the vaccines.  Why can't he go on his own or ask someone else for help. And if he is disabled or immobile and needs that assistance, how exactly is he going to go back to fishing on Shabbos on his own?

But anyway, the son asked if he is allowed to take his father for the vaccine, which will be assisting him in going back to his beloved activity of fishing. He wants his father to get vaccinated, so he will be safe and healthy, but it will assist him in being mechalel shabbos. So, he asked if he is allowed to or not.

The people at Lev L'Achim brought the question to Rav Yitzchak Zilbershtein, rav of Raat Elchonon neighborhood of Bnei Braq.

Rav Zilbershtein paskened that even though the father is also mechalel shabbos at home, it is different when he goes fishing as that makes him a mechalel shabbos bfarhesya -a public shabbos desecrater, which gives him a worse status in halacha. He said that the son should not assist in his father getting vaccinated and should put forth effort to prevent his father from getting vaccinated so he will not return to fishing.

source: Hamechadesh