Vaccination and health: no mandatory vaccination required.                                                              

No visa is required.

You can stay a maximum of three (3) months. If you have a multiple entry visa it must be valid for six (6) months. 

Documentation to present: Valid passport for at least 3 months, return ticket, and economic solvency for a minimum of US $500.00 upon entry to the country.

More information here.

Important

1. Any person of nationality requiring a visa to enter the Republic of Panama, who has a valid Visa or Residence, duly issued by Canada, United States of America, Commonwealth of Australia, Republic of Korea, State of Japan, United Kingdom of Great Britain and Northern Ireland, Republic of Singapore and any of the States that make up the European Union, may enter the national territory.
2. The visa granted by the countries mentioned in the previous article must be a multiple visa, have been previously used in the territory of the granting State and its validity shall not be less than six (6) months at the moment of entering Panamanian territory.
3. If you have a multiple entry visa with six (6) months of validity remaining from ONE of the following countries: Canada, United States of America, Commonwealth of Australia, Republic of Korea, State of Japan, United Kingdom of Great Britain and Northern Ireland, Republic of Singapore and any of the States that make up the European Union.
4. You must have used this visa to enter the country. For example, if you have a U.S. visa, you must have entered the U.S. on that visa to qualify for the waiver.

More datails here.