Unvaccinated people are still advised to avoid unnecessary travel.
The companies report that they have evaluated the data from over 44,000 participants aged 16 years and older.
Global travel, the guidance warns, poses "additional risks", and "even fully vaccinated travelers are at increased risk for getting and possibly spreading new Covid-19 variants". There were only nine cases of COVID-19, and they all happened in the placebo group.
They said that corresponded to an efficacy rate of 91.3 percent in preventing symptomatic cases "measured seven days through up to six months after the second dose".
More than one in five adults in the United States is now fully vaccinated, CDC director Rochelle Walensky said at a briefing.
Khan said the update reinforces the safety and effectiveness of the vaccines, and is another incentive for people to get vaccinated.
"Fully vaccinated" is defined as a person being two weeks out from the second of a two-dose vaccine like Pfizer's and Moderna's or from a one-dose vaccine like Johnson & Johnson's.
The new guidance greenlights vaccinated grandparents getting on airplanes to see grandchildren, for example, and says COVID-19 testing and quarantining are not necessary before or after travel as long as take precautions such as wearing masks and maintaining social distance. Scientists are unsure how much immunity people get from having COVID-19, and it's recommended that people who have had COVID-19 still get vaccinated.
The same rules apply to vaccinated people traveling internationally, with some exceptions.
Wolf tested positive for COVID-19 in December but said he felt no major symptoms.
USA air travel has begun rebounding - 1.6 million people passed through TSA checkpoints on Thursday, well above the 124,000 who did so a year before yet still below the 2.4 million from the same day in 2019.
Indeed, all USA airlines still require passengers to wear masks. The virus is spreading more rapidly in many places.
"Every day you get more data, and you change your guidance based on the existing data", said Dr. Ali Khan, dean of the University of Nebraska's College of Public Health.
However, the head of the CDC said at a press briefing Friday that she still recommends against non-essential travel - even for vaccinated people - but that the agency has a duty to update its guidance as more science becomes available.
- Chauvin Trial Day 3: Jurors, eyewitnesses watch body cam, surveillance footage
- Derek Chauvin is on trial for George Floyd's death
- Leaked WHO report points to animals as source of the pandemic
- Two US Capitol police officers injured after suspect rams auto into barrier
- Jury in George Floyd murder trial shown harrowing video of his death
- Four reported dead, two wounded in mass shooting south of Los Angeles
- Hundreds gather for 'Stop Asian hate' rally in Calgary
- Derek Chauvin Told Witness George Floyd Was "Probably On Something"
- Suez Canal ship 'now moving,' owner and officials say
- Myanmar protests: Death toll passes 500