Insufficient data. Nothing published to support conferred immunity. Onus is on claimant to prove immunity. Not the other way around.
There's no onus to prove anything to anyone else for one making a personal choice. If one thinks it's safe to travel to Coz then they can travel to Coz and need not prove to anyone that it is safe. They are free to look at what data is available - published and peer-reviewed or not - and make their own choices based on that.