(my emphasis embedded above)
I don't think such "vaccinate on arrival" offer even makes practical sense for border protection because vaccines do not work straight away: a host develops anti-bodies during 2-3 weeks after the injection and then becomes immune and does not catch potential virus and consequently is less likely to be a "spreading machine" in the community he interacts with. So, in a case like Joker, an alien visiting Australia for couple weeks up to a month, his vaccination on arrival would not affect his danger to Aus public health, but would have an effect starting from about his planned leave, e.g. in his home country. this is not in Australian interest.
Of course my idea of "punishment by vaccination" is a satire. And a bit more seriously a social lesson for Joker teaching him that he's not a god and should follow the rules. And an analogy how society treats people who break the law: e.g. in prison, everyone is forced to follow the rules - if vaxxing needed no ? asked everyone must obey, anti-vaxxer or not. Joker broke the rules, so some adequate punishment be in order.
Finally the second part of punishment by forfeiting prize money to a refugee org, is the most serious idea of mine: Joker could have used his celebrity status to stand for his fellow refugees but in his narcissistic mind, he didn't say anything about them refugees, even if his father hinted him for it...