You may find that the numbers blow the herd immunity theory out of the window?
No, because reality is more complicated like that what you want to construct.
btw, I have written it above: tourists are likely to be better vaccinated then the people they visit.
Also, if you remember that for certain illnesses the vaccination rate in the whole world is above 80%, the "tourist threat" does not seem that big, right?
Your intentions (and outcome) is very clear, it is simply not possible, even before you've seen the evidence - your mind is made up.
You haven't looked into the vaccination rates in Cairns, or the number of tourists that visit the city in the peak months - in fact you haven't looked at any of the metrics that I suggested.
I asked for more evidence and I will wait for it to come in before closing my mind.