Worldwide situation. General considerations
Due to the advancement of vaccination worldwide, documentation and testing restrictions have been eliminated in many countries. In fact, in some countries, by presenting the complete vaccination certificate against Coronavirus, RT-PCR or antigen test results are no longer required, nor is a health affidavit form. In other cases, such as Mexico, some countries in Latin America and Europe, they do not require a vaccination certificate either.
However, we insist once again, that in the situation of constant changes, it is always important to ask and arrange details with the airline and, if necessary, with the Chicago O'Hare airport (ORD)
as well as, in the case of international flights, with the embassy or consulate near the final destination, and also with the countries involved for connecting flights, if any.