Great item, but it'll only be good for a max of 21-30 days once it's unrefrigerated. (below 30c). Once the solution goes above 8c there's no way of preserving that degradation. There's no way you can keep it that cool in the post.

What you need for postal is the dried form i.e. lyophilised + a source of bacteriostatic water. The dried form is room temp stable for months out of the fridge. Once mixed the usual rules apply.

I'm not saying the shot won't work after 30 days, but there's a risk of bacterial infection and exacerbated side effects.