Doctors advise against traveling immediately after your vaccination. Here's why.

The coronavirus vaccines are welcome news to restless travelers. But if you’re planning to take a trip as soon as you get your shot or shots, depending on which vaccine you receive, not so fast: Vaccinated individuals should wait at least two weeks after their last shot, according to doctors and the Centers for Disease Control and Prevention. In addition, some countries and cruise lines are echoing the call for vaccinated travelers to delay their visits.

Medical experts say the two-week time frame allows the vaccine to do its job. "Our bodies need that time to develop both antibody and cellular immune responses, which are critical for protection," said Paul Sax, clinical director of the Division of Infectious Diseases at Brigham and Women’s Hospital in Boston.

Sten Vermund, dean of the Yale School of Public Health in New Haven, Connecticut, said the first shot can provide partial protection. But, "to maximize the protection you get from the vaccine," he said, "you should be two weeks beyond your second dose before you expose yourself in travel or other somewhat higher-risk circumstances." The recommendation applies to Pfizer and Moderna’s vaccines, which entail two shots, and Johnson and Johnson’s, which features a single dose.

The CDC changed its long-held position against all but essential travel with an April 2 announcement that fully vaccinated people — meaning those who have received two Moderna or Pfizer shots or a single J & J shot and waited the requisite amount of time afterward — can safely move about the country.

For domestic trips, the CDC said people can skip bookended testing as well as self-quarantining. "You do NOT need to get tested or self-quarantine if you are fully vaccinated or have recovered from COVID-19 in the past 3 months," the agency stated. For international travel, visitors must follow the country’s entry guidelines and will need to present a negative test result to return to the States.

Health-care professionals still advise caution when traveling because none of the vaccines is 100% effective against infection. "There are millions of people who have been vaccinated, and if 5% of them get covid, that would be a lot of people with covid," said Emily Landon, an infectious diseases specialist at the University of Chicago Medicine.

The rise in variants also poses a concern, because it’s not yet clear how much protection the vaccines provide against those more highly transmissible strains.

It’s also not clear whether fully vaccinated individuals can contract and transmit covid-19 asymptomatically. Even though a recent study released by the CDC found that the Pfizer and Moderna vaccines cut down on asymptomatic transmission, the CDC continues to urge vaccinated individuals to wear masks and socially distance when out in public. Masks are required on all forms of U.S. public transportation, such as planes and trains, and inside transportation hubs, such as airports and bus stations.

Travel health notice information can be found on the Centers for Disease Control and Prevention's interactive map showing travel recommendations by destination and the CDC's travel health notice webpage.