What is the safest country to seek refuge in the event of a zombie apocalypse?

With the popularisation of zombie apocalypse movies like World War Z and the Walking Dead, I can't help but think of such a potential situation arising in the future.

I would think small countries that are protected from all sides by natural defences like Switzerland would be easier to safeguard? Bigger countries like the USA and China may have to work on strengthening their respective walls, but their vast borders makes it really hard to prevent any gaps in defence.