The CDC has updated its recommendations on polio vaccination for
travelers in light of the World Health Organization’s recent
declaration of polio as a public health emergency of international
concern.

The CDC recommends that people planning to travel to a country with
active wild poliovirus receive the inactivated poliovirus (IPV)
booster. Travelers should document proof of immunization in the yellow
International Certificate of Vaccination to avoid travel delays. The
U.S. is not planning to change its requirements for U.S. entry.

In its declaration, the WHO noted that 10 countries have ongoing
poliovirus transmission:

Cameroon, Pakistan, and Syria have recently exported wild poliovirus.
Residents and people traveling to these countries for more than 4
weeks are required to receive IPV or oral polio vaccine 4 to 52 weeks
before departing these countries.
Afghanistan, Equatorial Guinea, Ethiopia, Iraq, Israel, Somalia, and
Nigeria are infected with poliovirus but have not yet exported it.
Residents and long-term travelers to these countries are encouraged to
get boosters.

CDC health advisory