For example, 27 countries said that they required yellow fever vaccinations for travelers coming straight from the United States.

This is mandatory for countries that require proof of yellow fever vaccination upon entry, but it's a good idea to carry it wherever you travel.

You will need a yellow fever vaccination if arriving from an infected area within five days.

A list of the countries that require yellow fever vaccination is published by the WHO.

If you do not have evidence of a yellow fever vaccination, you may be denied entry or required to pay a fine.

Proof of yellow fever vaccination is only required if you are coming from an infected area.

The form must be presented at certain international border crossings as proof of yellow fever vaccination.

They are also to provide evidence of yellow fever vaccination.

Proof of yellow fever vaccination is required for entry.

Proof of yellow fever vaccination may also be required if travelling from an infected area.