The Centers for Disease Control and Prevention (CDC) updated its coronavirus travel guidelines on Friday to say that vaccinated people can now move about the country "safely."
It also said fully vaccinated US residents can travel abroad, given that they are "less likely to get and spread Covid-19," but cautioned that destination countries likely have their own requirements.
After a slow start, the US vaccine rollout has been accelerating in recent months and is now averaging about 2.5 million doses administered per day and sometimes surpassing 3 million.
The new rules will be a shot in the arm to the struggling tourism industry, after a year in which people were told to avoid all non-essential travel.
The US has approved three vaccines. The Pfizer/BioNTech and Moderna vaccines require two doses, spaced over several weeks, to be fully vaccinated. The Johnson & Johnson vaccine requires only one jab.
Wear masks, avoid crowds
The CDC still recommends wearing face masks and avoiding crowds.
US residents who are fully vaccinated can also travel abroad again, the CDC said, but much depends on the rules of the destination country - and a slew of travel restriction still apply, such as between the US and Europe.
The CDC points out that the destination country may require a coronavirus test before US departure. But quarantine upon return to the United States would not be necessary.
The health agency had relaxed guidelines on social contact restrictions in early March, stating that fully vaccinated people could now once again gather indoors in small private gatherings without masks and without minimum spacing. But at that time the agency still strongly advised against non-essential travel.