Yes, but I'm just trying to think about how you would go about setting up such a trial? What would the parameters be that you're looking at to determine if the trial is a success or not? Or is just to measure peoples compliance with staying at home?
Say, you took Singapore as a low risk country. Someone who is in Singapore, regardless of vaccination status, has a low probability of having the virus, as it has not been allowed to "let rip". So what would the result really mean? You took 100 travellers from Singapore, half vaccinated and half not vaccinated, and with PCR test 72 hours prior to departure (as currently required), with only 3- 5 new cases a day in a population of 5,500,000 the chance of someone testing positive in the 3 days after they've had their test is probably in the order of 1 in 365,000... so in 100 travellers per day you might expect a positive once every 10 years.
It's probably more meaningful for countries like US, UK, where there are strong vaccination rates but also still significant amounts of community transmission.