Nationals from the US, Canadian, EU, Australian, and New Zealand don’t need a visa to travel to the Channel Islands for up to six months, which is lumped together with the UK mainland as a “common travel area.” Visitors from the European Schengen can stay for up to 90 days visa-free. Vaccinations are not needed.
Health and Safety
Alderney is one of the safest places you could visit in the world. Locals are typically very friendly and the town is small and generally free of violent crime. The only real problem is with drunken guests in the streets at bar closing times, though this is not endemic or anywhere near as bad as the UK mainland.
Health standards in Alderney are on par with England, with clinics and a small hospital, and there are no exotic diseases worry about. All visitors (including UK citizens) will have to pay for treatment as the European EHIC health card is not recognized, making travel insurance a must. Be careful on the more rugged southern coast and for high tides and surf in general.