Data: Sherpa; Chart: Will Chase/AxiosYou've got your COVID vaccine, and the CDC says it's OK to travel this summer, even internationally. But you're likely to find that your overseas options are limited by border restrictions in many countries.Why it matters: If you don't do your homework before traveling, you could wind up stranded in a foreign airport or quarantined in your hotel room for two weeks.Stay on top of the latest market trends and economic insights with Axios Markets. Subscribe for freeReopening international travel is not a one-sided decision. While the United States is ahead of most of the world on vaccinations, other countries like France are imposing new lockdowns amid fresh COVID surges as they wait for more vaccines to become available.Knowing when and where it is safe to travel is confusing, especially because the rules change frequently. Catch up fast: First, it's important to understand the CDC's updated travel guidance, issued April 2. Fully vaccinated travelers no longer have to take a test before going abroad, and can avoid quarantine on their return. But they still need to get tested three days before they board a plane back to the U.S., and they should also monitor themselves for any symptoms and get tested three to five days after returning home. When traveling within the U.S., fully vaccinated people do not need to be tested before or after their trip, and they don't need to quarantine either. In all cases, travelers should wear a mask, stay six feet away from others and wash their hands often. What's happening: Many airlines and travel companies are bending over backwards to help people sift through the rules and manage all the new requirements.Sherpa, which specializes in international visa requirements, has created an interactive map that shows the level of restrictions Americans will encounter in each country. The PC Agency, a UK travel consultancy, created a traffic light system that designates countries as red, yellow or green, depending on their level of restrictions. Lonely Planet has also produced a guide that lists the countries vaccinated Americans can visit without major restrictions.What they're saying: If you want to go to Albania, Costa Rica, the Dominican Republic, Mexico or Tanzania, you're good to go. There are no restrictions, even for those who are not vaccinated. Other destinations, including many in the Caribbean, Eastern Europe and Africa, require visitors to have a negative COVID test before arrival. Some require a mandatory quarantine even with a negative test, although a few, like Iceland, have created new exemptions for vaccinated travelers.Many popular travel destinations, including France, Germany, Spain and Greece, remain off limits for visitors. The catch: The trickiest part of international travel might be getting home. All travelers, including vaccinated Americans, need to test negative before boarding their return flight. "It is one of the big obstacles to getting travel going again, which is why some consumers are holding back. It's the fear of testing positive," Paul Charles, founder of the PC Agency, tells Axios. What to watch: Charles expects a safe travel corridor to open up between the U.S. and the U.K. soon, and the rest of Europe to open up to Americans by early July. In the meantime, airlines and cruise operators are bending over backwards to try to help passengers manage it all. American Airlines helps passengers check the travel requirements for their destination, arrange a pre-flight COVID test if necessary and securely upload documents to a mobile health passport app called VeriFLY.United Airlines offers similar help through its Travel-Ready Center.Viking is the first cruise line to add full-scale PCR testing labs on all of its ocean ships. It's part of a plan to resume cruises in June for vaccinated passengers, starting with Bermuda, Iceland and the UK.The bottom line: As travel slowly resumes, creating peace of mind for passengers is the number one focus, says travel consultant Shashank Nigram, CEO of Simpliflying. "This will be part of the travel psyche going forward."Like this article? Get more from Axios and subscribe to Axios Markets for free.